+publisher:"Virginia Tech" +contributor:("Long, Timothy E.")

Virginia Tech

1. Cashman, Mark Francis. Siloxane-Based Reinforcement of Polysiloxanes: from Supramolecular Interactions to Nanoparticles.

Degree: MS, Macromolecular Science and Engineering, 2020, Virginia Tech

URL: http://hdl.handle.net/10919/100134

► Polysiloxanes, also referred to as 'silicones' encompass a unique and important class of polymers harboring an inorganic backbone. Polysiloxanes, especially poly(dimethyl siloxane) (PDMS) the flagship… (more)

▼ Polysiloxanes, also referred to as 'silicones' encompass a unique and important class of polymers harboring an inorganic backbone. Polysiloxanes, especially poly(dimethyl siloxane) (PDMS) the flagship polymer of the family, observe widespread utilization throughout industry and academia thanks to a plethora of desirable properties such as their incredible elongation potential, stability to irradiation, and facile chemical tunability. A major complication with the utilization of polysiloxanes for mechanical purposes is their poor resistance to defect propagation and material failure. As a result polysiloxane materials ubiquitously observe reinforcement in some fashion: reinforcement is achieved either through the physical or chemical incorporation of a reinforcing agent, such as fumed silica, or through the implementation of a chemical functionality that facilitates reinforcement via phase separation and strong associative properties, such as hydrogen bonding. This research tackles polysiloxane reinforcement via both of these strategies. Facile chemical modification permits the construction PDMS polymer chains that incorporate hydrogen bonding motifs, which phase separate to afford hydrogen bond-reinforced phases that instill vast improvements to elastic behavior, mechanical and elongation properties, and upper-use temperature. Novel nanocomposite formulation through the incorporation of MQ nanoparticles (which observe widespread usage in cosmetics) facilitate further routes toward improved mechanical and elongation properties. Furthermore, with growing interest in additive manufacturing strategies, which permit the construction of complex geometries via an additive approach (as opposed to conventional manufacturing processes, which require subtractive approaches and are limited in geometric complexity), great interest lies in the capability to additively manufacture polysiloxane-based materials. This work also illustrates the development of an MQ-reinforced polysiloxane system that is amenable to conventional vat photopolymerization additive manufacturing: chemical modification of PDMS polymer chains permits the installation of UV-activatable crosslinking motifs, allowing solid geometries to be constructed from a liquid precursor formulation. Advisors/Committee Members: Long, Timothy E. (committeechair), Williams, Christopher Bryant (committee member), Bortner, Michael J. (committee member).

Subjects/Keywords: Siloxane; polysiloxane; poly(dimethyl siloxane) (PDMS); MQ copolymer nanoparticle; vat photopolymerization (VP); additive manufacturing (AM); 3D printing (3DP); 1; 3-bis(3-aminopropyl)tetramethyldisiloxane (BATS); chain extender; microphase separation

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APA (6^th Edition):

Cashman, M. F. (2020). Siloxane-Based Reinforcement of Polysiloxanes: from Supramolecular Interactions to Nanoparticles. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/100134

Chicago Manual of Style (16^th Edition):

Cashman, Mark Francis. “Siloxane-Based Reinforcement of Polysiloxanes: from Supramolecular Interactions to Nanoparticles.” 2020. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/100134.

MLA Handbook (7^th Edition):

Cashman, Mark Francis. “Siloxane-Based Reinforcement of Polysiloxanes: from Supramolecular Interactions to Nanoparticles.” 2020. Web. 13 Apr 2021.

Vancouver:

Cashman MF. Siloxane-Based Reinforcement of Polysiloxanes: from Supramolecular Interactions to Nanoparticles. [Internet] [Masters thesis]. Virginia Tech; 2020. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/100134.

Council of Science Editors:

Cashman MF. Siloxane-Based Reinforcement of Polysiloxanes: from Supramolecular Interactions to Nanoparticles. [Masters Thesis]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/100134

Virginia Tech

2. Dong, Shuping. Effects of acid hydrolysis conditions on cellulose nanocrystal yield and properties: A response surface methodology study.

Degree: MS, Macromolecular Science and Engineering, 2014, Virginia Tech

URL: http://hdl.handle.net/10919/78102

► Cellulose nanocrystals (CNCs) are frequently prepared by sulfuric acid hydrolysis of a purified cellulose starting material. CNC yields, however, are generally low, often below 20%.… (more)

▼ Cellulose nanocrystals (CNCs) are frequently prepared by sulfuric acid hydrolysis of a purified cellulose starting material. CNC yields, however, are generally low, often below 20%. This study employs response surface methodology to optimize the hydrolysis conditions for maximum CNC yield. Two experimental designs were tested and compared: the central composite design (CCD) and the Box–Behnken design (BBD). The three factors for the experimental design were acid concentration, hydrolysis temperature, and hydrolysis time. The responses quantified were CNC yield, sulfate group density, ζ-potential, z-average diameter, and Peak 1 value. The CCD proved suboptimal for this purpose because of the extreme reaction conditions at some of its corners, specifically (1,1,1) and (–1,–1, –1). Both models predicted maximum CNC yields in excess of 65% at similar sulfuric acid concentrations (~59 wt %) and hydrolysis temperatures (~65 °C). With the BBD, the hydrolysis temperature for maximum yield lay slightly outside the design space. All three factors were statistically significant for CNC yield with the CCD, whereas with the BBD, the hydrolysis time in the range 60–150 min was statistically insignificant. With both designs, the sulfate group density was a linear function of the acid concentration and hydrolysis temperature and maximal at the highest acid concentration and hydrolysis temperature of the design space. Both designs showed the hydrolysis time to be statistically insignificant for the ζ-potential of CNCs and yielded potentially data-overfitting regression models. With the BBD, the acid concentration significantly affected both the z-average diameter and Peak 1 value of CNCs. However, whereas the z-average diameter was more strongly affected by the hydrolysis temperature than the hydrolysis time, the Peak 1 value was more strongly affected by the hydrolysis time. The CCD did not yield a valid regression model for the Peak 1 data and a potentially data-overfitting model for the z-average diameter data. A future optimization study should use the BBD but slightly higher hydrolysis temperatures and shorter hydrolysis times than used with the BBD in this study (45–65 °C and 60–150 min, respectively). Advisors/Committee Members: Roman, Maren (committeechair), Renneckar, Scott (committee member), Long, Timothy E. (committee member).

Subjects/Keywords: cellulose nanocrystals; sulfuric acid hydrolysis; surface charge density; z-potential; particle size; yield; surface response method; central composite design; Box-Behnken Design

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APA (6^th Edition):

Dong, S. (2014). Effects of acid hydrolysis conditions on cellulose nanocrystal yield and properties: A response surface methodology study. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78102

Chicago Manual of Style (16^th Edition):

Dong, Shuping. “Effects of acid hydrolysis conditions on cellulose nanocrystal yield and properties: A response surface methodology study.” 2014. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/78102.

MLA Handbook (7^th Edition):

Dong, Shuping. “Effects of acid hydrolysis conditions on cellulose nanocrystal yield and properties: A response surface methodology study.” 2014. Web. 13 Apr 2021.

Vancouver:

Dong S. Effects of acid hydrolysis conditions on cellulose nanocrystal yield and properties: A response surface methodology study. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/78102.

Council of Science Editors:

Dong S. Effects of acid hydrolysis conditions on cellulose nanocrystal yield and properties: A response surface methodology study. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/78102

Virginia Tech

3. Lambert, Philip Michael. Design and Fabrication of a Mask Projection Microstereolithography System for the Characterization and Processing of Novel Photopolymer Resins.

Degree: MS, Mechanical Engineering, 2014, Virginia Tech

URL: http://hdl.handle.net/10919/50515

► The goal of this work was to design and build a mask projection microstereolithography (MPμSL) 3D printing system to characterize, process, and quantify the performance… (more)

▼ The goal of this work was to design and build a mask projection microstereolithography (MPμSL) 3D printing system to characterize, process, and quantify the performance of novel photopolymers. MPμSL is an Additive Manufacturing process that uses DLP technology to digitally pattern UV light and selectively cure entire layers of photopolymer resin and fabricate a three dimensional part. For the MPμSL system designed in this body of work, a process was defined to introduce novel photopolymers and characterize their performance. The characterization process first determines the curing characteristics of the photopolymer, namely the Critical Exposure (Ec) and Depth of Penetration (Dp). Performance of the photopolymer is identified via the fabrication of a benchmark test part, designed to determine the minimum feature size, XY plane accuracy, Z-axis minimum feature size, and Z-axis accuracy of each photopolymer with the system. The first characterized photopolymer was poly (propylene glycol) diacrylate, which was used to benchmark the designed MPμSL system. This included the achievable XY resolution (212 micrometers), minimum layer thickness (20 micrometers), vertical build rate (360 layers/hr), and maximum build volume (6x8x36mm3). This system benchmarking process revealed two areas of underperformance when compared to systems of similar design, which lead to the development of the first two research questions: (i) 'How does minimum feature size vary with exposure energy?' and (ii) 'How does Z-axis accuracy vary with increasing Tinuvin 400 concentration in the prepolymer?' The experiment for research question (i) revealed that achievable feature size decreases by 67% with a 420% increase in exposure energy. Introducing 0.25wt% of the photo-inhibitor Tinuvin 400 demonstrated depth of penetration reduction from 398.5 micrometers to 119.7 micrometers. This corresponds to a decrease in Z-axis error from 119% (no Tinuvin 400) to 9% Z-axis error (0.25% Tinuvin 400). Two novel photopolymers were introduced to the system and characterized. Research question (iii) asks 'What are the curing characteristics of Pluronic L-31 how does it perform in the MPμSL system?' while Research Question 4 similarly queries 'What are the curing characteristics of Phosphonium Ionic Liquid and how does it perform in the MPμSL system?' The Pluronic L-31 with 2wt% photo-initiator had an Ec of 17.2 mJ/cm2 and a Dp of 288.8 micrometers, with a minimum feature size of 57.3 ± 5.7 micrometers, with XY plane error of 6% and a Z-axis error of 83%. Phosphonium Ionic Liquid was mixed in various concentrations into two base polymers, Butyl Diacrylate (0% PIL and 10% PIL) and Poly Ethylene Dimethacrylate (5% PIL, 15% PIL, 25% PIL). Introducing PIL into either base polymer caused the Ec to increase in all samples, while there is no significant trend between increasing concentrations of IL in either PEGDMA or BDA and depth of penetration. Any trends previously identified between penetration depth and Z accuracy do not seem to extend from one resin to… Advisors/Committee Members: Williams, Christopher Bryant (committeechair), Long, Timothy E. (committee member), Bickford, Lissett R. (committee member).

Subjects/Keywords: Mask Projection Microstereolithography; Stereolithography; Vat Polymerization; Tissue Scaffolds; Novel Photopolymer

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APA (6^th Edition):

Lambert, P. M. (2014). Design and Fabrication of a Mask Projection Microstereolithography System for the Characterization and Processing of Novel Photopolymer Resins. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50515

Chicago Manual of Style (16^th Edition):

Lambert, Philip Michael. “Design and Fabrication of a Mask Projection Microstereolithography System for the Characterization and Processing of Novel Photopolymer Resins.” 2014. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/50515.

MLA Handbook (7^th Edition):

Lambert, Philip Michael. “Design and Fabrication of a Mask Projection Microstereolithography System for the Characterization and Processing of Novel Photopolymer Resins.” 2014. Web. 13 Apr 2021.

Vancouver:

Lambert PM. Design and Fabrication of a Mask Projection Microstereolithography System for the Characterization and Processing of Novel Photopolymer Resins. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/50515.

Council of Science Editors:

Lambert PM. Design and Fabrication of a Mask Projection Microstereolithography System for the Characterization and Processing of Novel Photopolymer Resins. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/50515

Virginia Tech

4. Kletetschka, Karel. 3D Printing of Specialty Devices for Geochemical Investigations: Real-Time Studies of Goethite and Schwertmannite Formation.

Degree: MS, Geosciences, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/96191

► New types of laboratory reactors that are highly customizable, low-cost and easy to produce are needed to investigate low-temperature geochemical processes. We recently showed that… (more)

Subjects/Keywords: 3D-Printing; Custom Reactors; In-situ Experiments; Schwertmannite; Goethite

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APA (6^th Edition):

Kletetschka, K. (2018). 3D Printing of Specialty Devices for Geochemical Investigations: Real-Time Studies of Goethite and Schwertmannite Formation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/96191

Chicago Manual of Style (16^th Edition):

Kletetschka, Karel. “3D Printing of Specialty Devices for Geochemical Investigations: Real-Time Studies of Goethite and Schwertmannite Formation.” 2018. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/96191.

MLA Handbook (7^th Edition):

Kletetschka, Karel. “3D Printing of Specialty Devices for Geochemical Investigations: Real-Time Studies of Goethite and Schwertmannite Formation.” 2018. Web. 13 Apr 2021.

Vancouver:

Kletetschka K. 3D Printing of Specialty Devices for Geochemical Investigations: Real-Time Studies of Goethite and Schwertmannite Formation. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/96191.

Council of Science Editors:

Kletetschka K. 3D Printing of Specialty Devices for Geochemical Investigations: Real-Time Studies of Goethite and Schwertmannite Formation. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/96191

Virginia Tech

5. Young, Taylor Tront. Lipid Bilayer Formation in Aqueous Solutions of Ionic Liquids.

Degree: MS, Mechanical Engineering, 2012, Virginia Tech

URL: http://hdl.handle.net/10919/35292

► The formation of lipid bilayer membranes between droplets of ionic liquid is presented as a means of forming functional bimolecular networks for use in sensor… (more)

Subjects/Keywords: Alamethicin; Ionic Liquid; Lipid Bilayer; Droplet Interface Bilayer

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APA (6^th Edition):

Young, T. T. (2012). Lipid Bilayer Formation in Aqueous Solutions of Ionic Liquids. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35292

Chicago Manual of Style (16^th Edition):

Young, Taylor Tront. “Lipid Bilayer Formation in Aqueous Solutions of Ionic Liquids.” 2012. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/35292.

MLA Handbook (7^th Edition):

Young, Taylor Tront. “Lipid Bilayer Formation in Aqueous Solutions of Ionic Liquids.” 2012. Web. 13 Apr 2021.

Vancouver:

Young TT. Lipid Bilayer Formation in Aqueous Solutions of Ionic Liquids. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/35292.

Council of Science Editors:

Young TT. Lipid Bilayer Formation in Aqueous Solutions of Ionic Liquids. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/35292

Virginia Tech

6. Nebipasagil, Ali. Chemically and Photochemically Crosslinked Networks and Acid-Functionalized Mwcnt Composites.

Degree: MS, Macromolecular Science and Engineering, 2011, Virginia Tech

URL: http://hdl.handle.net/10919/42703

► PTMO-urethane and urea diacrylates (UtDA, UrDA) were synthesized from a two-step reactions of bis (4-isocyanatocyclohexyl) methane (HMDI) with either Î±,Ï -hydroxy-terminated poly (tetramethylene oxide) (PTMO… (more)

▼ PTMO-urethane and urea diacrylates (UtDA, UrDA) were synthesized from a two-step reactions of bis (4-isocyanatocyclohexyl) methane (HMDI) with either Î±,Ï -hydroxy-terminated poly (tetramethylene oxide) (PTMO Mn 250, 1000, 2000 and 2900 g/mol) or Î±,Ï -aminopropyl-terminated PTMO and 2-hydroxyethyl acrylate (HEA). PTMO-based ester precursors (EtDA) were also synthesized from Î±,Ï -hydroxy-terminated PTMO (Mn 1000 and 2000 g/mol). Two bis acetoacetates were synthesized from acetoacetylation of 1,4-butanediol and 250 g/mol hydroxy-terminated PTMO with tert-butyl acetoacetate. 1H NMR spectroscopy confirmed the structure and average molecular weights (Mn)of diacrylates. Mn of these precursors were in the range of 950 to 3670 g/mol by 1H NMR. The rheological properties of diacrylates were studied and activation energies for flow were calculated. Activation energies increased with increasing Mn and hydrogen-bond segment content. Michael carbon addition was employed to covalently crosslink the precursors resulting in networks with gel fractions better than 90%. DSC and DMA experiments revealed that networks had a broad distribution of glass transition temperatures depending on Mn and degree of hydrogen bonding present in the diacrylates. Their Tgâ s varied from -61 ÂºC to 63 ÂºC depending on the crosslinking density and hydrogen-bonding segment content. TGA revealed that UtDA and UrDA networks had an improved thermal stability compared to their EtDA counterparts. Tensile properties showed a variation depending on the structure and Mn of diacrylate and BisAcAc precursors. The storage moduli of networks precursor change from 25.3 MPa to 2.0 MPa with increasing Mn of the urethane diacrylate Elongation at break increased from 255% to 755 % for the same networks. The Youngâ s moduli increased from 3.27 MPa for EtDA 2000 to 311.1 MPa for UrDA 2000 which was attributed to increasing degree of hydrogen-bonding. Acid functionalization of C70 P Baytubes multiwalled carbon nanotubes (MWCNT) generated acid-functionalized nanotubes (MWCNT-COOH). Suspension of MWCNT-COOH in organic solvents (chloroform, toluene, THF, DMF and 2-propanol) were prepared. DLS indicated average particle diameters of MWCNT-COOH in DMF and in 2-propanol were 139 nm and 162 nm respectively. FESEM of suspensions revealed aggregate free dispersion of MWCNT-COOH in DMF and 2-propanol. MWCNT-COOH containing composite networks were prepared. FESEM images of fracture surfaces of UtDA showed MWCNT-COOH were well-dispersed in the composites. DMA showed an increase in the rubbery plateau modulus which correlated with the MWCNT-COOH content in the networks. Tensile testing also revealed a relationship between MWCNT-COOH content and youngâ s moduli and strain at break of networks. Storage moduli of networks increased from 25 MPa to 211 MPa with increasing MWCNT-COOH content whereas elongation at break decreased from 255 % to 146 %. UtDAs and pentaerythritol tetraacrylate (PETA) were crosslinked under UV radiation (6 passes, 1.42 Â± 0.05 W.cm2 for each pass) in the… Advisors/Committee Members: Long, Timothy E. (committeechair), Turner, S. Richard (committee member), Moore, Robert B. (committee member).

Subjects/Keywords: Michael carbon addition; urethane H-bonding; Telechelic; multiwalled carbon nanotubes; urethane composites; UV curing; thermo-mechanical property

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APA (6^th Edition):

Nebipasagil, A. (2011). Chemically and Photochemically Crosslinked Networks and Acid-Functionalized Mwcnt Composites. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42703

Chicago Manual of Style (16^th Edition):

Nebipasagil, Ali. “Chemically and Photochemically Crosslinked Networks and Acid-Functionalized Mwcnt Composites.” 2011. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/42703.

MLA Handbook (7^th Edition):

Nebipasagil, Ali. “Chemically and Photochemically Crosslinked Networks and Acid-Functionalized Mwcnt Composites.” 2011. Web. 13 Apr 2021.

Vancouver:

Nebipasagil A. Chemically and Photochemically Crosslinked Networks and Acid-Functionalized Mwcnt Composites. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/42703.

Council of Science Editors:

Nebipasagil A. Chemically and Photochemically Crosslinked Networks and Acid-Functionalized Mwcnt Composites. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/42703

Virginia Tech

7. Smith, Colin Frederick. Jellyfish Inspired Underwater Systems and Technologies.

Degree: MS, Mechanical Engineering, 2011, Virginia Tech

URL: http://hdl.handle.net/10919/76896

► Unmanned underwater vehicles (UUVs) have long been in use but increasingly there has been a wave of biomimetic robots taking over the duties and functions… (more)

Subjects/Keywords: robotic; vehicle; underwater; unmanned; biomimetic; jellyfish

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APA (6^th Edition):

Smith, C. F. (2011). Jellyfish Inspired Underwater Systems and Technologies. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/76896

Chicago Manual of Style (16^th Edition):

Smith, Colin Frederick. “Jellyfish Inspired Underwater Systems and Technologies.” 2011. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/76896.

MLA Handbook (7^th Edition):

Smith, Colin Frederick. “Jellyfish Inspired Underwater Systems and Technologies.” 2011. Web. 13 Apr 2021.

Vancouver:

Smith CF. Jellyfish Inspired Underwater Systems and Technologies. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/76896.

Council of Science Editors:

Smith CF. Jellyfish Inspired Underwater Systems and Technologies. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/76896

Virginia Tech

8. Skinner, Anna Penn. Ion Conducting Polyelectrolytes in Conductive Network Composites and Humidity Sensing Applications for Ionic Polymer-Metal Composite Actuators.

Degree: MS, Materials Science and Engineering, 2016, Virginia Tech

URL: http://hdl.handle.net/10919/71683

► Ionic polymer-metal composites (IPMCs) are widely studied for their potential as electromechanical sensors and actuators. Bending of the IMPC depends on internal ion motion under… (more)

Subjects/Keywords: Ionic self-assembled multilayers; Ionic polymer-metal composite; actuator; humidity sensor

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APA (6^th Edition):

Skinner, A. P. (2016). Ion Conducting Polyelectrolytes in Conductive Network Composites and Humidity Sensing Applications for Ionic Polymer-Metal Composite Actuators. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/71683

Chicago Manual of Style (16^th Edition):

Skinner, Anna Penn. “Ion Conducting Polyelectrolytes in Conductive Network Composites and Humidity Sensing Applications for Ionic Polymer-Metal Composite Actuators.” 2016. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/71683.

MLA Handbook (7^th Edition):

Skinner, Anna Penn. “Ion Conducting Polyelectrolytes in Conductive Network Composites and Humidity Sensing Applications for Ionic Polymer-Metal Composite Actuators.” 2016. Web. 13 Apr 2021.

Vancouver:

Skinner AP. Ion Conducting Polyelectrolytes in Conductive Network Composites and Humidity Sensing Applications for Ionic Polymer-Metal Composite Actuators. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/71683.

Council of Science Editors:

Skinner AP. Ion Conducting Polyelectrolytes in Conductive Network Composites and Humidity Sensing Applications for Ionic Polymer-Metal Composite Actuators. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/71683

Virginia Tech

9. Schultz, Alison. Functional Block Copolymers via Anionic Polymerization for Electroactive Membranes.

Degree: MS, Chemistry, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/51115

► Ion-containing block copolymers blend ionic liquid properties with well-defined polymer architectures. This provides conductive materials with robust mechanical stability, efficient processability, and tunable macromolecular design.… (more)

▼ Ion-containing block copolymers blend ionic liquid properties with well-defined polymer architectures. This provides conductive materials with robust mechanical stability, efficient processability, and tunable macromolecular design. Conventional free radical polymerization and anion exchange achieved copolymers containing n-butyl acrylate and phosphonium ionic liquids. These compositions incorporated vinylbenzyl triphenyl phosphonium and vinylbenzyl tricyclohexyl phosphonium cations bearing chloride (Cl), or bis(trifluoromethane sulfonyl)imide (Tf2N) counteranions. Differential scanning calorimetry and dynamic mechanical analysis provided corresponding thermomechanical properties. Factors including cyclic substituents, counteranion type, as well as ionic concentration significantly influenced phosphonium cation association. 1, 1\'-(1, 4-Butanediyl)bis(imidazole) neutralized NexarTM sulfonated pentablock copolymers and produced novel electrostatically crosslinked membranes. Variable temperature FTIR and 1H NMR spectroscopy confirmed neutralization. Atomic force microscopy and small angle X-ray scattering studied polymer morphology and revealed electrostatic crosslinking characteristics. Tensile analysis, dynamic mechanical analysis, thermogravimetric analysis, and vapor sorption thermogravimetric analysis investigated polymer properties. The neutralized polymer demonstrated enhanced thermal stability, decreased water adsorption, and well-defined microphase separation. These findings highlight NexarTM sulfonated pentablock copolymers as reactive platforms for novel, bis-imidazolium crosslinked materials. 4-Vinylbenzyl piperidine is a novel styrenic compound that observably autopolymerizes. In situ FTIR spectroscopy monitored styrene and 4-vinylbenzyl piperidine thermal polymerizations. A pseudo-first-order kinetic treatment of the thermal polymerization data provided observed rate constants for both monomers. An Arrhenius analysis derived thermal activation energy values. 4-Vinylbenzyl piperidine exhibited activation energy 80 KJ/mol less than styrene. The monomer differs from styrene in its piperidinyl structure. Consequently, in situ FTIR spectroscopy also monitored styrene thermal polymerization with variable N-benzyl piperidine concentrations. Under these circumstances, styrene revealed activation energy 60 KJ/mol less than its respective bulk value. The similarities in chemical structure between styrene and 4-vinylbenzyl piperidine suggested thermally initiated polymerization occurred by the Mayo mechanism. The unique substituent is proposed to offer additional cationic effects for enhancing polymerization rates. Living anionic polymerization of 4-vinylbenzyl piperidine achieved novel piperidinyl-containing polymers. Homopolymer and copolymer architectures of this design offer structural integrity, and emphasize base stability. Sequential anionic polymerization afforded a 10K g/mol poly(tert-butyl styrene-co-4-vinylbenzyl piperidine) diblock and a 50K poly(tert-butyl… Advisors/Committee Members: Long, Timothy E. (committeechair), Moore, Robert Bowen (committee member), McGrath, James E. (committee member).

Subjects/Keywords: water purification; random copolymer; ionic liquids; anionic polymerization; NexarTM; thermomechanical property

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APA (6^th Edition):

Schultz, A. (2013). Functional Block Copolymers via Anionic Polymerization for Electroactive Membranes. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/51115

Chicago Manual of Style (16^th Edition):

Schultz, Alison. “Functional Block Copolymers via Anionic Polymerization for Electroactive Membranes.” 2013. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/51115.

MLA Handbook (7^th Edition):

Schultz, Alison. “Functional Block Copolymers via Anionic Polymerization for Electroactive Membranes.” 2013. Web. 13 Apr 2021.

Vancouver:

Schultz A. Functional Block Copolymers via Anionic Polymerization for Electroactive Membranes. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/51115.

Council of Science Editors:

Schultz A. Functional Block Copolymers via Anionic Polymerization for Electroactive Membranes. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/51115

Virginia Tech

10. Zimmermann, Kristen Ann. Intracellular Transport in Cancer Treatments: Carbon Nanohorns Conjugated to Quantum Dots and Chemotherapeutic Agents.

Degree: MS, Biomedical Engineering, 2012, Virginia Tech

URL: http://hdl.handle.net/10919/72986

► Cancer therapies are often limited by bulk and cellular barriers to transport. Nanoparticle or chemotherapeutic compound intracellular transport has implications in understanding therapeutic effect and… (more)

▼ Cancer therapies are often limited by bulk and cellular barriers to transport. Nanoparticle or chemotherapeutic compound intracellular transport has implications in understanding therapeutic effect and toxicity. The scope of this thesis was to study the intracellular transport of carbon nanohorns and to improve the efficacy of various chemotherapeutic agents through increased intracellular transport. In the first study, fluorescent probes (quantum dots) were conjugated to carbon nanohorns to facilitate the optical visualization of the nanohorns. These hybrid particles were characterized with transmission electron microscopy, electron dispersive spectroscopy and UV-VIS/FL spectroscopy. Their cellular uptake kinetics, uptake efficiencies, and intracellular distribution were determined in three malignant cell lines (breast â€“ MDA-MB-231, bladder â€“ AY-27, and brain â€“ U87-MG) using flow cytometry and confocal microscopy. Intracellular distribution did not vary greatly between cell lines; however, the uptake kinetics and efficiencies were highly dependent on cell morphology. In the second study, the efficacy of various chemotherapeutic agents (i.e., doxorubicin, cisplatin, and carboplatin) was evaluated in AY-27 rat bladder transitional cell carcinoma cells. In the future, severe hyperthermia and chemothermotherapy (chemotherapy + hyperthermia) will also be evaluated. Doxorubicin and cisplatin compounds were more toxic compared to carboplatin. Hyperthermia has previously shown to increase the cellular uptake of chemotherapeutic agents; therefore, chemothermotherapy is expected to have synergistic effects on cell death. This work can then be translated to carbon nanohorn-based laser heating to generate thermal energy in a local region for delivery of high concentrations of chemotherapeutic agents. Although these two concepts are small pieces of the overall scope of nanoparticle-based therapies, they are fundamental to the advancement of such therapies. Advisors/Committee Members: Long, Timothy E. (committee member), Rylander, Christopher G. (committeecochair), Rylander, Marissa Nicole (committeecochair).

Subjects/Keywords: Cancer; Intracellular distribution; carbon nanohorn; cellular uptake kinetics; chemotherapy; hyperthermia; quantum dot; transport

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APA (6^th Edition):

Zimmermann, K. A. (2012). Intracellular Transport in Cancer Treatments: Carbon Nanohorns Conjugated to Quantum Dots and Chemotherapeutic Agents. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/72986

Chicago Manual of Style (16^th Edition):

Zimmermann, Kristen Ann. “Intracellular Transport in Cancer Treatments: Carbon Nanohorns Conjugated to Quantum Dots and Chemotherapeutic Agents.” 2012. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/72986.

MLA Handbook (7^th Edition):

Zimmermann, Kristen Ann. “Intracellular Transport in Cancer Treatments: Carbon Nanohorns Conjugated to Quantum Dots and Chemotherapeutic Agents.” 2012. Web. 13 Apr 2021.

Vancouver:

Zimmermann KA. Intracellular Transport in Cancer Treatments: Carbon Nanohorns Conjugated to Quantum Dots and Chemotherapeutic Agents. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/72986.

Council of Science Editors:

Zimmermann KA. Intracellular Transport in Cancer Treatments: Carbon Nanohorns Conjugated to Quantum Dots and Chemotherapeutic Agents. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/72986

Virginia Tech

11. Cao, Ke. Telechelic Polyetherimides with Functionalized End Groups for Enhancement of Mechanical Strength, Flame Retardancy, and Optical Properties.

Degree: MS, Macromolecular Science and Engineering, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/97831

► This thesis focuses on understanding the factors that affect the properties of polyetherimide (PEI) and improving the properties. As a high-performance thermoplastic resin, the first… (more)

▼ This thesis focuses on understanding the factors that affect the properties of polyetherimide (PEI) and improving the properties. As a high-performance thermoplastic resin, the first challenge in PEI application is its high processing temperature and viscosity. Therefore, two supramolecular strategies were applied to not only solve the problem of high processing temperature or viscosity but also enhance the mechanical and flame retardancy. In addition, the yellow to amber color of PEIs limits its applications in high-tech fields such as microelectronics and optoelectronics. Thus, a fundamental study of how end group and molecular weight affect the optical properties of PEIs provides a better knowledge of the mechanism and an effective strategy for designing PEIs. To lower the processing viscosity while maintaining or even improving the mechanical properties of PEI, the first strategy was to synthesize PEI oligomers, and incorporate self-complementary quadruple hydrogen bonding ureidopyrimidinone (UPy) units at the chain ends. Surprisingly, the UPy imparted PEI with a Mn as low as 8 kDa (8k-PEI) with great film formability. Excitingly, 8k-PEI-UPy exhibited an outstanding Young's modulus higher than those of state-of-the-art high-molecular-weight (high-MW) commercial PEIs. Therefore, the incorporation of UPy was proved to be an effective method to synthesize low-molecular-weight, high-mechanical-strength PEIs. Although low-molecular-weight PEI-UPy had high mechanical properties, its limited thermal stability and potentially low flame retardancy, however, restricted its applications in areas such as aerospace and aircrafts. Hence in another strategy, which utilize the phosphonium ionic groups were incorporated into PEI oligomers targeting at achieving high thermal stability, flame retardancy, and mechanical properties simultaneously. Functionalization of dianhydride-terminated PEI by tetraphenylphosphonium bromide afforded the synthesis of phosphonium bromide terminated PEI (PEI-PhPPh3Br), which simultaneously exhibited excellent thermal stability up to ~400°C, outstanding flame retardancy evidenced by high char yield and extremely high limiting oxygen index, and a very high mechanical strength. The study thus provides an efficient strategy to simultaneously enhance the thermal and mechanical properties as well as flame retardancy. Furthermore, the low-molecular-weight PEI-PhPPh3Br had good processability due to its strong shear thinning. In addition to the thermal and mechanical properties and flame retardancy, the end groups affect the optical properties, especially the yellowness, of PEIs. Understanding how end group and molecular weight affect the yellowness, of PEIs is critical for their applications in fields including optoelectronics and microelectronics. Thereby, PEIs with different Mn and various end groups including electron-withdrawing and electron-donating were prepared and characterized. Electron-withdrawing end groups reduced the yellowness and increased the transparency of PEI, regardless of the Mn.… Advisors/Committee Members: Liu, Guoliang (committeechair), Long, Timothy E. (committeechair), Moore, Robert Bowen (committee member).

Subjects/Keywords: Polyetherimide; ureidopyrimidinone; phosphonium; yellowness

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APA (6^th Edition):

Cao, K. (2018). Telechelic Polyetherimides with Functionalized End Groups for Enhancement of Mechanical Strength, Flame Retardancy, and Optical Properties. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/97831

Chicago Manual of Style (16^th Edition):

Cao, Ke. “Telechelic Polyetherimides with Functionalized End Groups for Enhancement of Mechanical Strength, Flame Retardancy, and Optical Properties.” 2018. Masters Thesis, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/97831.

MLA Handbook (7^th Edition):

Cao, Ke. “Telechelic Polyetherimides with Functionalized End Groups for Enhancement of Mechanical Strength, Flame Retardancy, and Optical Properties.” 2018. Web. 13 Apr 2021.

Vancouver:

Cao K. Telechelic Polyetherimides with Functionalized End Groups for Enhancement of Mechanical Strength, Flame Retardancy, and Optical Properties. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/97831.

Council of Science Editors:

Cao K. Telechelic Polyetherimides with Functionalized End Groups for Enhancement of Mechanical Strength, Flame Retardancy, and Optical Properties. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/97831

12. Meng, Xiangtao. Chemical Modification of Cellulose Esters for Oral Drug Delivery.

Degree: PhD, Macromolecular Science and Engineering, 2016, Virginia Tech

URL: http://hdl.handle.net/10919/71383

► Polymer functional groups have critical impacts upon physical, chemical and mechanical properties, and thus affect the specific applications of the polymer. Functionalization of cellulose esters… (more)

▼ Polymer functional groups have critical impacts upon physical, chemical and mechanical properties, and thus affect the specific applications of the polymer. Functionalization of cellulose esters and ethers has been under extensive investigation for applications including drug delivery, cosmetics, food ingredients, and automobile coating. In oral delivery of poorly water-soluble drugs, amorphous solid dispersion (ASD) formulations have been used, prepared by forming miscible blends of polymers and drugs to inhibit crystallization and enhance bioavailability of the drug. The Edgar and Taylor groups have revealed that some cellulose omega-carboxyalkanoates were highly effective as ASD polymers, with the pendant carboxylic acid groups providing both specific polymer-drug interactions and pH-triggered release through swelling of the ionized polymer matrix. While a variety of functional groups such as hydroxyl and amide groups are also of interest, cellulose functionalization has relied heavily on classical methods such as esterification and etherification for appending functional groups. These methods, although they have been very useful, are limited in two respects. First, they typically employ harsh reaction conditions. Secondly, each synthetic pathway is only applicable for one or a narrow group of functionalities due to restrictions imposed by the required reaction conditions. To this end, there is a great impetus to identify novel reactions in cellulose modification that are mild, efficient and ideally modular. In the initial effort to design and synthesize cellulose esters for oral drug delivery, we developed several new methods in cellulose functionalization, which can overcome drawbacks of conventional synthetic pathways, provide novel cellulose derivatives that are otherwise inaccessible, and present a platform for structure-property relationship study. Cellulose omega-hydroxyalkanoates were previously difficult to access as the hydroxyl groups, if not protected, react with carboxylic acid/carbonyl during a typical esterification reaction or ring opening of lactones, producing cellulose-g-polyester and homopolyester. We demonstrated the viability of chemoselective olefin hydroboration-oxidation in the synthesis of cellulose omega]-hydroxyesters in the presence of ester groups. Cellulose esters with terminally olefinic side chains were transformed to the target products by two-step, one-pot hydroboration-oxidation reactions, using 9-borabicyclo[3.3.1]nonane (9-BBN) as hydroboration agent, followed by oxidizing the organoborane intermediate to a primary alcohol using mildly alkaline H2O2. The use of 9-BBN as hydroboration agent and sodium acetate as base catalyst in oxidation successfully avoided cleavage of ester linkages by borane reduction and base catalyzed hydrolysis. With the impetus of modular and efficient synthesis, we introduced olefin cross-metathesis (CM) in polysaccharide functionalization. Using Grubbs type catalyst, cellulose esters with terminally olefinic side chains were… Advisors/Committee Members: Edgar, Kevin J. (committeechair), Turner, S. Richard (committee member), Taylor, Lynne S. (committee member), Matson, John (committee member), Long, Timothy E. (committee member).

Subjects/Keywords: cellulose esters; functionalization; amorphous solid dispersion; olefin metathesis; thiol-Michael addition; esterification; hydroboration oxidation; click reaction.

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APA (6^th Edition):

Meng, X. (2016). Chemical Modification of Cellulose Esters for Oral Drug Delivery. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/71383

Chicago Manual of Style (16^th Edition):

Meng, Xiangtao. “Chemical Modification of Cellulose Esters for Oral Drug Delivery.” 2016. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/71383.

MLA Handbook (7^th Edition):

Meng, Xiangtao. “Chemical Modification of Cellulose Esters for Oral Drug Delivery.” 2016. Web. 13 Apr 2021.

Vancouver:

Meng X. Chemical Modification of Cellulose Esters for Oral Drug Delivery. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/71383.

Council of Science Editors:

Meng X. Chemical Modification of Cellulose Esters for Oral Drug Delivery. [Doctoral Dissertation]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/71383

Virginia Tech

13. Tamami, Mana. Synthesis and characterization of ammonium ionenes containing hydrogen bonding functionalities.

Degree: PhD, Chemistry, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/19234

► Ammonium ionenes are polycations that have quaternary nitrogens in their macromolecular backbone and are synthesized via step-growth polymerization technique. They offer interesting coulombic properties, and… (more)

▼ Ammonium ionenes are polycations that have quaternary nitrogens in their macromolecular backbone and are synthesized via step-growth polymerization technique. They offer interesting coulombic properties, and the synthetic design provides control over charge density. Non-covalent interactions including nucleobase hydrogen bonding and electrostatics were studied in ammonium ionenes. The non-covalent interactions are expected to increase the effective molecular weight of polymeric precursors and induce microphase separation due to intermolecular associations. The influence of non-covalent interactions on structure-property relationships of ammonium ionenes were studied regarding mechanical (tensile, DMA), thermal (DSC, TGA), and morphological (AFM, SAXS) properties. Hydrogen bonding interaction (10-40 kJ/mol) was introduced using DNA nucleobase pairs such as adenine and thymine. Novel adenine and thymine functionalized segmented and non-segmented ammonium ionenes were successfully synthesized using Michael addition chemistry. In non-segmented systems, we investigated the influence of spacer length on homoassociation and heteroassociation of complementary nucleobase-containing ionenes. Based on DSC analyses, complementary non-segmented ionenes made miscible blends. The Tgs of ionene blends with shorter spacer length (4 bonds between the nucleobase and secondary amine in the polymer backbone) followed the Fox equation, which indicated no intermolecular interactions. The longer alkyl spacer (9 bonds between nucleobase and secondary amine in the polymer backbone) provided efficient flexibility for the self-assembly process to occur. Thus, increasing the spacer length from 4-bonds to 9-bonds, the Tgs of the blends deviated from both Fox and Gordon-Taylor equations and demonstrated the presence of hydrogen bonding interactions. In segmented systems, we investigated the association between nucleobase-containing ionenes and their complementary guest molecules. Job\'s method revealed a 1:1 stoichiometry for the hydrogen-bonded complexes. These association constants for the 1:1 complexes, based on the Benesi-Hildebrand model were 94 and 130 M-1 respectively, which were in agreement with literature values for adenine and thymine nucleobase pairs (10-100 M-1). DSC thermograms confirmed no macrophase separation for 1:1 [ionene-A/T]:[guest molecule] complexes based on the disappearance of the melting peak of the guest molecule. Morphological studies including atomic force microscopy (AFM) demonstrated a reduced degree of microphase separation for the 1:1 complexes due to the disruption of adenine-adenine or thymine-thymine interactions. Poly(dimethyl siloxane)-based ammonium ionenes having various hard segment contents were synthesized. The charge density or hard segment content was tuned for appropriate application using low molecular weight monomer. The change in hard segment content had a profound effect on thermal, mechanical, rheological, and gas permeability. Microphase separation was confirmed using DSC and DMA… Advisors/Committee Members: Long, Timothy E. (committeechair), Turner, S. Richard (committee member), Wilkes, Garth L. (committee member), Duncan, Susan E. (committee member).

Subjects/Keywords: Segmented ionenes; non-segmented ionenes; nucleobase; hydrogen bonding; Michael addition; self-healing; bio-adhesion; molecular

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APA (6^th Edition):

Tamami, M. (2013). Synthesis and characterization of ammonium ionenes containing hydrogen bonding functionalities. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/19234

Chicago Manual of Style (16^th Edition):

Tamami, Mana. “Synthesis and characterization of ammonium ionenes containing hydrogen bonding functionalities.” 2013. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/19234.

MLA Handbook (7^th Edition):

Tamami, Mana. “Synthesis and characterization of ammonium ionenes containing hydrogen bonding functionalities.” 2013. Web. 13 Apr 2021.

Vancouver:

Tamami M. Synthesis and characterization of ammonium ionenes containing hydrogen bonding functionalities. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/19234.

Council of Science Editors:

Tamami M. Synthesis and characterization of ammonium ionenes containing hydrogen bonding functionalities. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/19234

Virginia Tech

14. Nelson, Ashley Marie. Design of Functional Polyesters for Electronic and Biological Applications.

Degree: PhD, Chemistry, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/74914

► Melt polymerization and novel monomers enabled the synthesis of polyesters for electronic and biological applications. Inspiration from nature and a passion for environmental preservation instigated… (more)

▼ Melt polymerization and novel monomers enabled the synthesis of polyesters for electronic and biological applications. Inspiration from nature and a passion for environmental preservation instigated an emphasis on the incorporation of renewable resources into polymeric materials. Critical analysis of current research surrounding bisphenol-A replacements and ioncontaining segmented polyurethanes aided in identifying benchmark polymers, including limitations, challenges, and future needs. Structure-property-morphology relationships were investigated to evaluate the polymers for success in the proposed applications as well as to improve understanding of polyester compositions to further design and develop sophisticated polymers for emerging applications. Aiming to utilize the reported [2 + 2] cycloaddition of the known mesogen 4,4’-dimethyltrans-stilbene dicarboxylate (SDE) to overcome ultraviolet (UV) induced degradation issues in electronic encasings, the synthesis of copolyesters containing SDE ensued. 1,6-Hexanediol (HD) and 1,4-butanediol comonomers in varying weight ratios readily copolymerized with SDE under melt transesterification conditions to afford a systematic series of copolyesters. Differential scanning calorimetry revealed all copolyesters exhibited liquid crystalline transitions and melting temperatures ranged from 196 °C – 317 °C. Additionally, melt rheology displayed shear thinning to facilitate melt processing. Compression molded films exhibited high storage moduli, a glassy plateau until the onset of flow, and tensile testing revealed a Young’s iii modulus of ~900 MPa for poly(SDE-HD). These properties enable a wide range of working temperatures and environments for electronic applications. Adding complexity to linear liquid crystalline copolyesters, copolymerization with oligomeric hydroxyl-functionalized polyethers afforded segmented liquid crystalline copolyesters. 4,4’-Biphenyl dicarboxylate (BDE), commercially available diols containing 4, 5, 6, 8, or 10 methylene units, and introducing poly(tetramethylene oxide) or a Pluronic® triblock oligoethers in varying weight % were used to synthesize multiple series of segmented copolyesters. Comparing melting transitions as a function of methylene spacer length elucidated the expected even-odd effect and melting temperatures ranged from 150 °C to 300 °C. Furthermore, incorporating the flexible soft segment did not prevent formation of a liquid crystalline morphology. Complementary findings between differential scanning calorimetry and small-angle X-ray scattering confirmed a microphase-separated morphology. Thermomechanical analysis revealed tunable plateau moduli and temperature windows based on both soft segment content and methylene spacer length, and tensile testing showed the strain at break doubled from 75 weight % to 50 weight % hard segment content. The same compositions Young’s moduli decreased from 107 ± 12 MPa at 75 weight % hard segment to 19 ± 1 MPa with 50 weight % hard segment, demonstrating the mechanical trade-off and range of… Advisors/Committee Members: Long, Timothy E. (committeechair), Roman, Maren (committee member), Turner, S. Richard (committee member), Moore, Robert Bowen (committee member).

Subjects/Keywords: polyester; melt polymerization; renewable; gene delivery; liquid crystalline

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APA (6^th Edition):

Nelson, A. M. (2015). Design of Functional Polyesters for Electronic and Biological Applications. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/74914

Chicago Manual of Style (16^th Edition):

Nelson, Ashley Marie. “Design of Functional Polyesters for Electronic and Biological Applications.” 2015. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/74914.

MLA Handbook (7^th Edition):

Nelson, Ashley Marie. “Design of Functional Polyesters for Electronic and Biological Applications.” 2015. Web. 13 Apr 2021.

Vancouver:

Nelson AM. Design of Functional Polyesters for Electronic and Biological Applications. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/74914.

Council of Science Editors:

Nelson AM. Design of Functional Polyesters for Electronic and Biological Applications. [Doctoral Dissertation]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/74914

Virginia Tech

15. Savage, Alice. Synthesis and Solution Properties of Semi-rigid Polyelectrolytes and Polyampholytes.

Degree: PhD, Chemistry, 2014, Virginia Tech

URL: http://hdl.handle.net/10919/50820

► The incorporation of substituted stilbenes in copolymers affects the resulting solution properties and their controlled radical polymerizations. Substituted stilbene monomers readily polymerize in an alternating… (more)

Subjects/Keywords: Semi-rigid; polyelectrolytes; alternating copolymers; polyampholytes

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APA (6^th Edition):

Savage, A. (2014). Synthesis and Solution Properties of Semi-rigid Polyelectrolytes and Polyampholytes. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50820

Chicago Manual of Style (16^th Edition):

Savage, Alice. “Synthesis and Solution Properties of Semi-rigid Polyelectrolytes and Polyampholytes.” 2014. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/50820.

MLA Handbook (7^th Edition):

Savage, Alice. “Synthesis and Solution Properties of Semi-rigid Polyelectrolytes and Polyampholytes.” 2014. Web. 13 Apr 2021.

Vancouver:

Savage A. Synthesis and Solution Properties of Semi-rigid Polyelectrolytes and Polyampholytes. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/50820.

Council of Science Editors:

Savage A. Synthesis and Solution Properties of Semi-rigid Polyelectrolytes and Polyampholytes. [Doctoral Dissertation]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/50820

Virginia Tech

16. Margaretta, Evan David. Imparting Functionality to Macromolecules for Selective Stimulus Response.

Degree: PhD, Chemistry, 2016, Virginia Tech

URL: http://hdl.handle.net/10919/82226

► Polymeric materials with inherent stimulus response represent an ever-growing area of research. In particular, block copolymers demonstrate exciting properties owing to their enhanced mechanical strength… (more)

▼ Polymeric materials with inherent stimulus response represent an ever-growing area of research. In particular, block copolymers demonstrate exciting properties owing to their enhanced mechanical strength and microphase separation. Incorporating functionality into block copolymers proves useful in enhancing their utility. Presently, synthesis and subsequent post-polymerization modification achieved this for a range of block copolymers. In particular, neutralization of acid-containing polymers readily imparted ionic functionality and yielded microphase-separated block copolymer domains, enhancing polymer thermomechanical properties and ion transport. An ABA triblock copolymer composed of mechanically reinforcing polystyrene outer blocks and ionic central poly(1-methylimidazolium acrylate) block acted as a host for ionic liquid that caused an evolution in bulk morphology, resulting in enhanced ionic conductivity. The resulting membrane also exhibited a strong electromechanical actuation response under applied potential. Adding ionic liquid doped with a corresponding lithium salt enabled evaluation of sulfonated block copolymers as components of ternary polymer electrolytes, relevant for battery applications. Modification of a sulfonic acid-containing pentablock copolymer presented photocurable functional groups to the ionic domains which enabled their UV irradiation-induced curing. This novel route of modifying ion-containing block copolymers resulted in enhanced thermomechanical properties and enabled healing of physical defects in the film, unprecedented for ion-containing block copolymers. Covalent networks represent a relevant area of research for a wide variety of applications such as coatings, adhesives, and scaffolds. Careful design of degradable crosslinkers enables stimulus response in these networks by eliminating covalent crosslinks and affording a soluble product. Extension of poly(ethylene glycol) methacrylate-based network formation into three dimensions using microstereolithography resulted in novel acid-degradable 3D-printed parts. An additional study investigated mixtures of acrylamide-modified poly(vinyl alcohol) and poly(ethylene glycol) diacrylate as water-soluble resins for the direct formation of hydrogels from solution. Photorheology and photocalorimetry investigated the thermal and mechanical changes inherent in the curing process and evaluated the mixtures as a platform for microstereolithography. Advisors/Committee Members: Long, Timothy E. (committeechair), Moore, Robert Bowen (committee member), Turner, S. Richard (committee member), Heflin, James R. (committee member).

Subjects/Keywords: Ion-containing polymers; block copolymers; stimulus response; post-polymerization modification

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APA (6^th Edition):

Margaretta, E. D. (2016). Imparting Functionality to Macromolecules for Selective Stimulus Response. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/82226

Chicago Manual of Style (16^th Edition):

Margaretta, Evan David. “Imparting Functionality to Macromolecules for Selective Stimulus Response.” 2016. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/82226.

MLA Handbook (7^th Edition):

Margaretta, Evan David. “Imparting Functionality to Macromolecules for Selective Stimulus Response.” 2016. Web. 13 Apr 2021.

Vancouver:

Margaretta ED. Imparting Functionality to Macromolecules for Selective Stimulus Response. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/82226.

Council of Science Editors:

Margaretta ED. Imparting Functionality to Macromolecules for Selective Stimulus Response. [Doctoral Dissertation]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/82226

17. Zhang, Keren. Bio-inspired Design and Self-Assembly of Nucleobase- and Ion-Containing Polymers.

Degree: PhD, Chemistry, 2016, Virginia Tech

URL: http://hdl.handle.net/10919/73986

► Bio-inspired monomers functionalized with nucleobase or ionic group allowed synthesis of supramolecular polymers using free radical polymerization and controlled radical polymerization techniques. Comprehensive investigations for… (more)

▼ Bio-inspired monomers functionalized with nucleobase or ionic group allowed synthesis of supramolecular polymers using free radical polymerization and controlled radical polymerization techniques. Comprehensive investigations for the structure-property-morphology relationships of these supramolecular polymers elucidated the effect of noncovalent interactions on polymer physical properties and self-assembly behaviors. Reverse addition-fragmentation chain transfer (RAFT) polymerization afforded acrylic ABC and ABA triblock copolymers with nucleobase-functionalized external blocks and a low-Tg central block. The hard-soft-hard triblock polymer architecture drove microphase-separation into a physically crosslinked hard phase in a low Tg matrix. Hydrogen bonding in the hard phase enhanced the mechanical strength and maintained processability of microphase-separated copolymers for thermoplastics and elastomers. A thermodynamically favored one-to-one stoichiometry of adenine and thymine yielded the optimal thermomechanical performance. Intermolecular hydrogen bonding of two thymine units and one adenine unit allowed the formation of base triplets and directed self-assembly of ABC triblock copolymers into remarkably well-defined lamellae with long-range ordering. Acetyl protected cytosine and guanine-containing random copolymers exhibited tunable cohesive strength and peel strength as pressure sensitive adhesives. Post-functionalization converted unprotected cytosine pendent groups in acrylic random copolymers to ureido-cytosine units that formed quadruple self-hydrogen bonding. Ureido-cytosine containing random copolymers self-assembled into nano-fibrillar hard domains in a soft acrylic matrix, and exhibited enhanced cohesive strength, wide service temperature window, and low moisture uptake as soft adhesives. A library of styrenic DABCO salt-containing monomers allowed the synthesis of random ionomers with two quaternized nitrogen cations on each ionic pendant group. Thermomechanical, morphological, and rheological analyses revealed that doubly-charged DABCO salts formed stronger ionic association and promoted more well-defined microphase-separation compared to singly-charged analogs with the same charge density. Bulkier counterions led to enhanced thermal stability, increased phase-mixing, and reduced water uptake for DABCO salt-containing copolymers, while alkyl substituent lengths only significantly affected water uptake of DABCO salt-containing copolymers. Step growth polymerization of plant oil-based AB monomer and diamines enabled the synthesis of unprecedented isocyanate-free poly(amide hydroxyurethane)s, the first examples of film-forming, linear isocyanate-free polyurethanes with mechanical integrity and processability. Successful electrospinning of segmented PAHUs afforded randomly orientated, semicrystalline fibers that formed stretchable, free-standing fiber mats with superior cell adhesion and biocompatibility. Advisors/Committee Members: Long, Timothy E. (committeechair), Moore, Robert Bowen (committee member), Grove, Tijana (committee member), Turner, S. Richard (committee member).

Subjects/Keywords: noncovalent interaction; hydrogen bonding; ionic interaction; nucleobase; DABCO salt; self-assembly; microphase-separation; non-isocyanate polyurethane

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APA (6^th Edition):

Zhang, K. (2016). Bio-inspired Design and Self-Assembly of Nucleobase- and Ion-Containing Polymers. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/73986

Chicago Manual of Style (16^th Edition):

Zhang, Keren. “Bio-inspired Design and Self-Assembly of Nucleobase- and Ion-Containing Polymers.” 2016. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/73986.

MLA Handbook (7^th Edition):

Zhang, Keren. “Bio-inspired Design and Self-Assembly of Nucleobase- and Ion-Containing Polymers.” 2016. Web. 13 Apr 2021.

Vancouver:

Zhang K. Bio-inspired Design and Self-Assembly of Nucleobase- and Ion-Containing Polymers. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/73986.

Council of Science Editors:

Zhang K. Bio-inspired Design and Self-Assembly of Nucleobase- and Ion-Containing Polymers. [Doctoral Dissertation]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/73986

Virginia Tech

18. Heifferon, Katherine Valentine. Designing Functionality into Step-Growth Polymers from Liquid Crystallinity to Additive Manufacturing.

Degree: PhD, Chemistry, 2019, Virginia Tech

URL: http://hdl.handle.net/10919/99829

► Step-growth polymerization facilitates the synthesis of a wide range of industrially applicable polymers, such as polyesters and polysulfones. The choice of backbone and end group… (more)

▼ Step-growth polymerization facilitates the synthesis of a wide range of industrially applicable polymers, such as polyesters and polysulfones. The choice of backbone and end group structure within these polymers drastically impacts the final material properties and processability emphasizing the necessity for thorough understanding of structure-property relationships. Seemingly simple changes, such as exchanging a monomer for its regioisomer, affects the polymers fundamental packing structure triggering a domino effect ultimately influencing the morphological, thermal, mechanical and barrier properties. In conjunction, end groups provide a means by which tunable mechanical properties and application into unique processing methods can be achieved. Synthesizing polyesters with bibenzoate based monomers generates a large range of morphologies. Linear, 4,4' bibenzoate (4,4'BB), is widely considered a mesogenic monomer due to its ability to impart a liquid crystalline (LC) morphology on semi-aromatic polyesters with linear aliphatic spacers. In this body of work, semi-aromatic polyesters using one of 4,4'BB's regioisomers, either 3,4'BB or 3,3'BB, largely resulted in amorphous or semi-crystalline polymers depending on the selection of aliphatic diol. Incorporation of the meta isomer (3,4'BB) into traditionally LC polymers, such as poly(diethylene glycol 4,4'-bibenzoate) and poly(butylene 4,4'-bibenzoate), through copolymerization afforded two polymer series with tunable LC properties. The 3,4'BB exhibited selective disruption of crystalline domains over the LC phase generating a number of polymers with LC glass morphologies. The application of 3,4'BB to a fully-aromatic polyester enabled the synthesis of a novel melt-processable homopolyester with high thermal stability, poly(p-phenylene 3,4' bibenzoate). This structure afforded a nematic LC morphology which revealed beneficial shear-thinning properties similar to industrial standards. The unique LC morphology of this homopolyester inspired further characterization of the range of achievable properties using the basic structure, poly(phenylene bibenzoate), with all the possible regioisomers. This study afforded six polymers systematically varied in chain linearity from a completely meta to a completely para backbone configuration. A range of morphologies were achieved from high Tg amorphous polymers for the meta configurations to semi-crystalline or LC in the polymers with greater linearity. End group functionalization generates influence on polymer properties while limiting the impact on beneficial properties achieved through the backbone structure and packing. Post-polymerization reactions or the addition of a monofunctional endcapper to the polymerization both achieve end group control. In this dissertation, the addition of a monofunctional diester with a sulfonate moiety to a semi-aromatic LC polyester synthesis resulted in a telechelic ionomer. The non-covalent interaction of the ionic groups will hopefully improve the compression and transverse mechanical… Advisors/Committee Members: Long, Timothy E. (committeechair), Turner, S. Richard (committee member), Moore, Robert Bowen (committee member), Williams, Christopher Bryant (committee member).

Subjects/Keywords: polyesters; polysulfones; liquid crystalline; additive manufacturing; step-growth polymerization

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Heifferon, K. V. (2019). Designing Functionality into Step-Growth Polymers from Liquid Crystallinity to Additive Manufacturing. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/99829

Chicago Manual of Style (16^th Edition):

Heifferon, Katherine Valentine. “Designing Functionality into Step-Growth Polymers from Liquid Crystallinity to Additive Manufacturing.” 2019. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/99829.

MLA Handbook (7^th Edition):

Heifferon, Katherine Valentine. “Designing Functionality into Step-Growth Polymers from Liquid Crystallinity to Additive Manufacturing.” 2019. Web. 13 Apr 2021.

Vancouver:

Heifferon KV. Designing Functionality into Step-Growth Polymers from Liquid Crystallinity to Additive Manufacturing. [Internet] [Doctoral dissertation]. Virginia Tech; 2019. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/99829.

Council of Science Editors:

Heifferon KV. Designing Functionality into Step-Growth Polymers from Liquid Crystallinity to Additive Manufacturing. [Doctoral Dissertation]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/99829

Virginia Tech

19. Edling, Hans Eliot. Synthesis and Structure-Property Relationships of Polyesters Containing Rigid Aromatic Structures.

Degree: PhD, Chemistry, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/95029

► Polyesters are an attractive class of polymer that can be readily modified with a wide range of different comonomers, during polymerization or with melt blending,… (more)

▼ Polyesters are an attractive class of polymer that can be readily modified with a wide range of different comonomers, during polymerization or with melt blending, to achieve a wide variety of physical properties. This research primarily focuses on polyesters that incorporate rigid aromatic structures that have excellent potential to enhance thermal and mechanical properties. Copolyesters were prepared through melt polycondensation of diesters and diols in the presence of an exchange catalyst. Monomer incorporation was verified with nuclear magnetic resonance (NMR) and molecular weights were obtained by measuring inherent viscosity (ninh). Physical properties were assessed with thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and rheology. Mechanical properties were assessed with tensile and impact testing. Copolyesters of poly(ethylene terephthalate) (PET) were synthesized by substituting dimethyl terephthalate (DMT) with dimethyl 4,4'-biphenyldicarboxylate (4,4'BB) resulting in enhanced glass transition (Tg) temperatures relative to PET while affording melting temperatures (Tm) low enough to allow facile melt processing. Further modification with dimethyl isophthalate (DMI) or dimethyl 3,4'-biphenyldicarboxylate (3,4'BB) slowed crystallization sufficiently to allow biaxial orientation, leading to further studies assessing the permeability of oriented films. Novel amorphous polyesters were synthesized with 3,4'BB or 4,4'BB in combination with neopentyl glycol (NPG), 1,4-cyclohexandimethanol (CHDM) and ethylene glycol (EG). Use of multiple diols produced clear, amorphous copolyesters with Tgs as high at 129 C. A series of novel high temperature(Tm) copolyesters were synthesized from dimethyl 2,6-naphthalenedicarboxylate (DMN) and 4,4'BB combined with CHDM. Studies were performed with standard DSC and thin film calorimetry to show the convergence of multiples melting endotherms in an effort to determine their origin. Preliminary work was performed on the modification of poly(1,4-cyclohexylenedimethylene terephthalate) (PCT), poly(1,4-cyclohexylenedimethylene 2,6-naphthalate) (PCN) and poly(1,4-cyclohexylenedimethylene 4,4'-bibenzoate) (PCB) with dimethyl p-terphenyl-4,4''-dicarboxylate. Advisors/Committee Members: Turner, S. Richard (committeechair), Long, Timothy E. (committee member), Gandour, Richard D. (committee member), Moore, Robert Bowen (committee member).

Subjects/Keywords: aromatic polyesters; biphenyl; crystallinity; amorphous; melt-phase polymerization; melting temperature; glass transition; permeability; stability; impact

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Edling, H. E. (2018). Synthesis and Structure-Property Relationships of Polyesters Containing Rigid Aromatic Structures. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/95029

Chicago Manual of Style (16^th Edition):

Edling, Hans Eliot. “Synthesis and Structure-Property Relationships of Polyesters Containing Rigid Aromatic Structures.” 2018. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/95029.

MLA Handbook (7^th Edition):

Edling, Hans Eliot. “Synthesis and Structure-Property Relationships of Polyesters Containing Rigid Aromatic Structures.” 2018. Web. 13 Apr 2021.

Vancouver:

Edling HE. Synthesis and Structure-Property Relationships of Polyesters Containing Rigid Aromatic Structures. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/95029.

Council of Science Editors:

Edling HE. Synthesis and Structure-Property Relationships of Polyesters Containing Rigid Aromatic Structures. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/95029

Virginia Tech

20. Zhang, Musan. Advancing Step-Growth Polymers: Novel Macromolecular Design and Electrostatic Interactions in Polyesters and Polyurethanes.

Degree: PhD, Chemistry, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/23239

► Conventional melt transesterification successfully synthesized high molecular weight segmented copolyesters. The cycloaliphatic monomers 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) and dimethyl-1,4-cyclohexane dicarboxylate (DMCD) afforded sterically hindered, ester carbonyls in… (more)

▼ Conventional melt transesterification successfully synthesized high molecular weight segmented copolyesters. The cycloaliphatic monomers 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) and dimethyl-1,4-cyclohexane dicarboxylate (DMCD) afforded sterically hindered, ester carbonyls in high-Tg polyester precursors. Reaction between the polyester polyol precursor and a primary or secondary alcohol at melt polymerization temperatures revealed reduced transesterification of the polyester hard segment as a result of enhanced steric hindrance adjacent to the ester linkages. Subsequent polymerization of a 4,000 g/mol polyol with monomers comprising the low-Tg block yielded high molecular weight polymers that exhibited enhanced mechanical properties compared to a non-segmented copolyester control. Atomic force microscopy uncovered unique needle-like, interconnected, microphase separated surface morphologies, and small-angle X-ray scattering confirmed the presence of bulk microphase separation. This new synthetic strategy enabled selective control of ionic charge placement into the hard segment or soft segment block of segmented copolyesters using melt transesterification. The ionic placement impacted the microphase-separated morphology, which influenced its thermomechanical properties and resulting mechanical performance. Melt transesterification of low-Tg, sodium sulfonated copolyesters achieved up to 15 mol% ionic content. The 10 and 15 mol% sodium sulfonated copolyesters exhibited water-dispersibility, which enabled cation dialysis exchanges to divalent metal cations. The sulfonated copolyesters containing divalent metal cations exhibited enhanced rubbery plateau moduli to higher temperatures. Novel trialkylphosphonium ionic liquids chain extenders enabled the successful synthesis of poly(ethylene glycol)-based, cationic polyurethanes with pendant phosphoniums in the hard segments (HS). Aqueous size exclusion chromatography (SEC) confirmed the charged polyurethanes, which varied the phosphonium alkyl substituent length (ethyl and butyl) and cationic HS content (25, 50, 75 mol%), achieved high absolute molecular weights. Dynamic mechanical analysis (DMA) demonstrated the triethylphosphonium (TEP) and tributylphosphonium (TBP) polyurethanes displayed similar thermomechanical properties, including increased rubbery plateau moduli and flow temperatures. Fourier transform infrared spectroscopy (FTIR) emphasized the significance of ion-dipole interaction on hydrogen bonding. Atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD) supported microphase separated morphologies in the trialkylphosphonium polyurethanes, despite the presence of ionic interactions. Sorption isotherm experiments revealed TBP polyurethanes displayed similar water sorption profiles to the noncharged analogue and lower water absorptivity compared to TEP. The phosphonium polyurethanes displayed significantly improved tensile strain; however, lower tensile stress of the TEP polyurethane… Advisors/Committee Members: Long, Timothy E. (committeechair), Turner, S. Richard (committee member), Whittington, Abby R. (committee member), Moore, Robert Bowen (committee member).

Subjects/Keywords: Step-growth polymers; polyesters; ionomers; polyurethanes; morphology

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Zhang, M. (2013). Advancing Step-Growth Polymers: Novel Macromolecular Design and Electrostatic Interactions in Polyesters and Polyurethanes. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/23239

Chicago Manual of Style (16^th Edition):

Zhang, Musan. “Advancing Step-Growth Polymers: Novel Macromolecular Design and Electrostatic Interactions in Polyesters and Polyurethanes.” 2013. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/23239.

MLA Handbook (7^th Edition):

Zhang, Musan. “Advancing Step-Growth Polymers: Novel Macromolecular Design and Electrostatic Interactions in Polyesters and Polyurethanes.” 2013. Web. 13 Apr 2021.

Vancouver:

Zhang M. Advancing Step-Growth Polymers: Novel Macromolecular Design and Electrostatic Interactions in Polyesters and Polyurethanes. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/23239.

Council of Science Editors:

Zhang M. Advancing Step-Growth Polymers: Novel Macromolecular Design and Electrostatic Interactions in Polyesters and Polyurethanes. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/23239

Virginia Tech

21. Mondschein, Ryan Joseph. Structure-Property Relationships of Polyester Regioisomers and Pendant Functionalized Polyetherimides.

Degree: PhD, Chemistry, 2019, Virginia Tech

URL: http://hdl.handle.net/10919/101706

► Step-growth polymerization enabled the synthesis of novel polyester regioisomers and pendant functionalized polyetherimides (PEI)s. Novel monomers incorporated at targeted mol % produced series of polyesters… (more)

▼ Step-growth polymerization enabled the synthesis of novel polyester regioisomers and pendant functionalized polyetherimides (PEI)s. Novel monomers incorporated at targeted mol % produced series of polyesters and PEIs, suitable for systematic analysis of key polymer properties. Subsequent compositional, thermal, mechanical, and rheological characterization forged structure-property relationships to further understand the influence of composition on performance. Altering regiochemistry is a subtle way to maintain the same polymer composition but tune desired properties. Similarly, introducing functional pendant groups expands the property profile of common industrial polymers and installs a handle for secondary chemistry after synthesizing the main polymer. Both altering regiochemistry and adding pendant groups alters polymer properties without the need for large changes in synthetic requirements or reaction conditions, ideal for industrial adoption. Incorporation of a kinked bibenzoate (BB)-based diester monomers into the commonly utilized linear regioisomer afforded processable amorphous and semi-aromatic (co)polyesters. BB-(co)polyesters with ethylene glycol (EG) possessed improved barrier performance compared to poly(ethylene terephthalate) (PET) while improving on mechanical properties, including tensile and flexural modulus/strength, rivaling bisphenol-A polycarbonate (BPA-PC). Replacement of EG with 1,4-cyclohexanedimethanol (CHDM) improved thermal properties closer to BPA-PC, while enabling melt rheological analysis due to its amorphous morphology. Time-temperature superposition (TTS) analysis produced master curves provided insight into the entanglement molecular weight (Me) and entanglement density. More kinked structures possessed a lower Me and more entanglements. Introducing kinked monomers posed the question of cyclic speices generation during polymerization, common in step-growth reactions. Thus, systematic incorporation of meta-substituted hydroxyethylresorcinol and para-substituted hydroxyethylhydroquinone regioisomers into PET analogues enabled the characterization of cyclic formation due to monomer regioisomers. Increased meta substitution produced increased amounts of cylic species, analyzed by size exclusion chromatography (SEC). Adding functionality to high performance polyetherimides (PEI)s is difficult due to the high temperatures required for processing. The lack of thermal stability for commonly utilized H-bonding/reactive groups limits viable moieties. Utilizing the high temperture processing, PEIs incorporating pendant carboxylic acids reacted in the melt to form branched PEIs. These branched PEIs exhibited steeper shear thinning as well as improved flame resistance, limited in thin film commercial PEIs. Advisors/Committee Members: Long, Timothy E. (committeechair), Turner, Sam Richard (committee member), Moore, Robert Bowen (committee member), Cheng, Shengfeng (committee member).

Subjects/Keywords: polyester; regioisomers; barrier; permeability; cyclics; entanglement; polyetherimides; branching; flame resistance; processability; pendant groups

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Mondschein, R. J. (2019). Structure-Property Relationships of Polyester Regioisomers and Pendant Functionalized Polyetherimides. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/101706

Chicago Manual of Style (16^th Edition):

Mondschein, Ryan Joseph. “Structure-Property Relationships of Polyester Regioisomers and Pendant Functionalized Polyetherimides.” 2019. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/101706.

MLA Handbook (7^th Edition):

Mondschein, Ryan Joseph. “Structure-Property Relationships of Polyester Regioisomers and Pendant Functionalized Polyetherimides.” 2019. Web. 13 Apr 2021.

Vancouver:

Mondschein RJ. Structure-Property Relationships of Polyester Regioisomers and Pendant Functionalized Polyetherimides. [Internet] [Doctoral dissertation]. Virginia Tech; 2019. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/101706.

Council of Science Editors:

Mondschein RJ. Structure-Property Relationships of Polyester Regioisomers and Pendant Functionalized Polyetherimides. [Doctoral Dissertation]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/101706

Virginia Tech

22. Fox, Stephen Carter. Regioselective Synthesis of Novel Cellulose Derivatives for Drug Delivery.

Degree: PhD, Macromolecular Science and Engineering, 2011, Virginia Tech

URL: http://hdl.handle.net/10919/77263

► New methods were developed for the regioselective synthesis of new classes of cellulose derivatives with properties that could help improve the delivery of pharmaceutical drugs… (more)

▼ New methods were developed for the regioselective synthesis of new classes of cellulose derivatives with properties that could help improve the delivery of pharmaceutical drugs within the human body. The specific synthetic targets of this research were regioselectively carboxylated and regioselectively aminated cellulose derivatives. While different avenues to the carboxylated cellulose were ultimately explored without success, a new method for the synthesis of selectively O-acylated 6-amino-6-deoxy-cellulose esters was devised. A key reaction that enabled the synthesis of the new cellulose derivatives described in this dissertation was the one-pot conversion of microcrystalline cellulose to 6-bromo-6-deoxy-cellulose esters. This reaction resulted in the highly selective displacement of the primary hydroxyl groups attached to the 6-carbon (C-6) on each anhydroglucose unit (AGU) in cellulose with bromide, with little or no bromination occurring at carbons 2 and 3 (C-2 and C-3). The brominated cellulose was then completely esterified by adding acetic, propionoic, or butyric acid anhydride to the reaction solution. The reaction products were readily soluble in many common organic solvents, including acetone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, and chloroform. It was shown that the bromides could be converted to iodides under Finkelstein reaction conditions. The presence of halides at C-6 allows a variety of new functional groups to be regioselectively introduced to cellulose via nucleophilic substitution. In one case, the 6-bromo-6-deoxy-cellulose esters were reacted with sodium cyanide to produce regioselectively synthesized cellulose nitriles. These compounds were synthesized with the idea that they could be converted to regioselectively carboxylated cellulose derivatives as an alternative pathway to the rhodium-catalyzed carbonyl insertion reactions also attempted in this research. However, the cellulose nitriles were highly susceptible to alkaline degradation, and conversion to the carboxylated cellulose was not achieved. The 6-bromo-6-deoxy-cellulose esters were also reacted with sodium azide to successfully produce 6-azido-6-deoxy-cellulose esters. The azide groups were then reduced to amines using the Staudinger reaction. This very mild and selective reaction allowed the conversion of the azides to amines in the presence of the ester groups still attached to the cellulose backbone. Such derivatives could have properties useful for a range of biomedical applications, including the delivery of anionic drugs. Advisors/Committee Members: Edgar, Kevin J. (committeechair), Frazier, Charles E. (committee member), Hanson, Brian E. (committee member), Roman, Maren (committee member), Long, Timothy E. (committee member).

Subjects/Keywords: drug delivery; Staudinger reduction; cellulose; regioselective synthesis; cellulose derivatives

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Fox, S. C. (2011). Regioselective Synthesis of Novel Cellulose Derivatives for Drug Delivery. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77263

Chicago Manual of Style (16^th Edition):

Fox, Stephen Carter. “Regioselective Synthesis of Novel Cellulose Derivatives for Drug Delivery.” 2011. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/77263.

MLA Handbook (7^th Edition):

Fox, Stephen Carter. “Regioselective Synthesis of Novel Cellulose Derivatives for Drug Delivery.” 2011. Web. 13 Apr 2021.

Vancouver:

Fox SC. Regioselective Synthesis of Novel Cellulose Derivatives for Drug Delivery. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/77263.

Council of Science Editors:

Fox SC. Regioselective Synthesis of Novel Cellulose Derivatives for Drug Delivery. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/77263

Virginia Tech

23. Green, Matthew Dale. Tailoring Structure and Function of Imidazole-Containing Block Copolymers for Emerging Applications from Gene Delivery to Electromechanical Devices.

Degree: PhD, Chemical Engineering, 2011, Virginia Tech

URL: http://hdl.handle.net/10919/40352

► The imidazole ring offers great potential for a variety of applications including gene delivery vectors, ionic liquids, electromechanical actuators, and novel monomers and polymers. The… (more)

▼ The imidazole ring offers great potential for a variety of applications including gene delivery vectors, ionic liquids, electromechanical actuators, and novel monomers and polymers. The imidazole ring provides a unique building block for these applications due to its thermal stability, aromatic nature, ability to form ionic salts, and ease of functionalization. Free radical polymerization of 1-vinylimidazole (1-VIm) and free radical copolymerizations with methyl methacrylate (MMA) and n-butyl acrylate (nBA) afforded homopolymers and copolymers with tunable solution and thermal properties. Aqueous SEC provided reproducible and reliable molecular weights for poly(1-VIm) in the absence of polymer aggregates. Analysis of the thermal properties revealed ideal random copolymers with MMA and non-ideal copolymers with nBA. Small angle X-ray scattering determined that the spacing between ionic groups remained constant with increased nonionic comonomer incorporation while the spacing between adjacent polymer backbones increased. Functionalization of 1-VIm with varying length alkyl halides and polymerization prepared a series of imidazolium homopolymers. Anion exchange reactions controlled the thermal and solution properties, and the bromide counteranion quantitatively exchanged to tetrafluoroborate (BF4), trifluoromethanesulfonate (TfO), and bis(trifluoromethanesulfonyl)imide (Tf2N). Thermogravimetric analysis revealed that thermal stability increased with decreased alkyl substituent length and larger counteranion size, and differential scanning calorimetry determined that glass transition temperature (Tg) decreased with increased alkyl substituent length and larger counteranion size. Electrochemical impedance spectroscopy determined the ionic conductivities of the imidazolium homopolymers, and analysis using the Vogel-Fulcher-Tammann equation revealed that the activation energy of ion conduction increased as alkyl substituent length increased. Polymer morphology determined using X-ray scattering also influenced the ionic conductivity. As the alkyl substituent length increased, the spacing between adjacent polymer backbones increased, which decreased the ionic conductivity due to the ion-hopping mechanism of ion conduction. Unsuccessful attempts to control the radical polymerization of 1-VIm led to the investigation of 1-(4-vinylbenzyl)imidazole (VBIm), which is a styrenic-based monomer with excellent propagating radical stability. Triblock copolymers incorporating VBIm monomer into a soft random copolymer center block and reinforcing, hard segment outer blocks provided a template for tuning the properties of the ionomer membranes for electroactive devices. Analysis of the morphology and mechanical properties using small angle X-ray scattering and dynamic mechanical analysis determined microphase separation and optimal mechanical properties for electromechanical transducer fabrication. Testing electromechanical transducers revealed superior performance relative to the benchmark NafionÂ®. Optimization of triblock… Advisors/Committee Members: Long, Timothy E. (committeechair), Walz, John Y. (committee member), Baird, Donald G. (committee member), Davis, Richey M. (committeecochair).

Subjects/Keywords: imidazole; block copolymers; ionenes; nitroxide-mediated polymerization; gene delivery; ionic polymer transducers; ionic conductivity

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Green, M. D. (2011). Tailoring Structure and Function of Imidazole-Containing Block Copolymers for Emerging Applications from Gene Delivery to Electromechanical Devices. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/40352

Chicago Manual of Style (16^th Edition):

Green, Matthew Dale. “Tailoring Structure and Function of Imidazole-Containing Block Copolymers for Emerging Applications from Gene Delivery to Electromechanical Devices.” 2011. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/40352.

MLA Handbook (7^th Edition):

Green, Matthew Dale. “Tailoring Structure and Function of Imidazole-Containing Block Copolymers for Emerging Applications from Gene Delivery to Electromechanical Devices.” 2011. Web. 13 Apr 2021.

Vancouver:

Green MD. Tailoring Structure and Function of Imidazole-Containing Block Copolymers for Emerging Applications from Gene Delivery to Electromechanical Devices. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/40352.

Council of Science Editors:

Green MD. Tailoring Structure and Function of Imidazole-Containing Block Copolymers for Emerging Applications from Gene Delivery to Electromechanical Devices. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/40352

Virginia Tech

24. Scott, Philip Jonathan. Advancing Elastomers to Additive Manufacturing Through Tailored Photochemistry and Latex Design.

Degree: PhD, Macromolecular Science and Engineering, 2020, Virginia Tech

URL: http://hdl.handle.net/10919/99311

► Additive manufacturing (AM) revolutionizes the fabrication of complex geometries, however the utility of these 3D objects for real world applications remains hindered by characteristically poor… (more)

Subjects/Keywords: polymer latex colloids; additive manufacturing; elastomers; polydienes; vat photopolymerization

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Scott, P. J. (2020). Advancing Elastomers to Additive Manufacturing Through Tailored Photochemistry and Latex Design. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/99311

Chicago Manual of Style (16^th Edition):

Scott, Philip Jonathan. “Advancing Elastomers to Additive Manufacturing Through Tailored Photochemistry and Latex Design.” 2020. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/99311.

MLA Handbook (7^th Edition):

Scott, Philip Jonathan. “Advancing Elastomers to Additive Manufacturing Through Tailored Photochemistry and Latex Design.” 2020. Web. 13 Apr 2021.

Vancouver:

Scott PJ. Advancing Elastomers to Additive Manufacturing Through Tailored Photochemistry and Latex Design. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/99311.

Council of Science Editors:

Scott PJ. Advancing Elastomers to Additive Manufacturing Through Tailored Photochemistry and Latex Design. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/99311

Virginia Tech

25. Fahs, Gregory Bain. The Effect of Ionomer Architecture on the Morphology in Gel State Functionalized Sulfonated Syndiotactic Polystyrene.

Degree: PhD, Chemistry, 2020, Virginia Tech

URL: http://hdl.handle.net/10919/97193

► Polymers are a class of chemicals that are defined by having a very large set of molecules that are chemically linked together where each unit… (more)

▼ Polymers are a class of chemicals that are defined by having a very large set of molecules that are chemically linked together where each unit (monomer) is repeated within the chemical structure. In particular, this dissertation focuses on the construction what are termed as "blocky" copolymers, which are defined by having two chemically different monomers that are incorporated in the polymer chain. The "blocky" characteristic of these polymers means that these two different monomers are physically segregated from each other on the polymer chain, where long portions of the chain that are of one type, followed by another section of the polymer that has the other type of monomer. The goal of creating this type of structure is to try to take advantage of the properties of both types of monomers, which can create materials with superior synergistic properties. In this case a hydrophobic (water hating) monomer is combined with a hydrophilic (water loving) chain. This hydrophobic component in the polymer is able to crystallize, which provides mechanical and thermal stability in the material by acting as a physical tether to hold neighboring chains together. With the other set of hydrophilic monomers, which in this case have an ionic component incorporated, we can now take advantage of this chemical components ability to aide in the transportation of ions. Transportation of ions is useful in a variety of commercially relevant applications, two of the most important applications of these ionic materials is in membranes that can be used to purify water or membrane materials in fuel cell technologies, specifically for proton exchange membranes. The focus of this research in particular was to create a simple synthesis technique that can create these blocky polymer chain architectures, which is done by performing the reaction while the polymer is made into a gel. The key to this is that the crystals within the gel act as a barrier to chemical reactions, creating conditions where we have substantial portions of the material that are able to be functionalized and the crystals within the material that are protected from being functionalized. By looking at the thermal characteristics, such as melting temperatures and amount of crystals within these systems we have seen that functionalizing these polymers in the heterogeneous gel state gives substantially better properties than functionalizing these materials randomly. Much like oil and water, incompatible polymer chains will phase separate from each other. In this case the hydrophobic and ionic components will phase separate from each other. The shape and distribution of these phase separated structure will dictate many of the material properties, which can be described by modeling the data collected from x-ray scattering experiments. All of this information will tell us based on the initial conditions that these polymers were created in, what properties should be expected based on the morphology and thermal behavior. This gives a better understanding of how to fine tune these… Advisors/Committee Members: Moore, Robert Bowen (committeechair), Long, Timothy E. (committee member), Cheng, Shengfeng (committee member), Liu, Guoliang (committee member).

Subjects/Keywords: gel-state; post-polymerization functionalization; sulfonation; heterogeneous; blocky; microstructure; syndiotactic polystyrene; small-angle x-ray scattering; wide-angle x-ray diffraction; ultra-small angle x-ray scattering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Fahs, G. B. (2020). The Effect of Ionomer Architecture on the Morphology in Gel State Functionalized Sulfonated Syndiotactic Polystyrene. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/97193

Chicago Manual of Style (16^th Edition):

Fahs, Gregory Bain. “The Effect of Ionomer Architecture on the Morphology in Gel State Functionalized Sulfonated Syndiotactic Polystyrene.” 2020. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/97193.

MLA Handbook (7^th Edition):

Fahs, Gregory Bain. “The Effect of Ionomer Architecture on the Morphology in Gel State Functionalized Sulfonated Syndiotactic Polystyrene.” 2020. Web. 13 Apr 2021.

Vancouver:

Fahs GB. The Effect of Ionomer Architecture on the Morphology in Gel State Functionalized Sulfonated Syndiotactic Polystyrene. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/97193.

Council of Science Editors:

Fahs GB. The Effect of Ionomer Architecture on the Morphology in Gel State Functionalized Sulfonated Syndiotactic Polystyrene. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/97193

26. Rezaei Mojdehi, Ahmad. Experimental and Theoretical Studies of Friction and Adhesion of Elastomeric Materials.

Degree: PhD, Engineering Mechanics, 2017, Virginia Tech

URL: http://hdl.handle.net/10919/79818

► In this dissertation, four distinct but in some ways related topics, mostly related to experimental and theoretical investigations of friction and adhesion of elastomeric materials,… (more)

▼ In this dissertation, four distinct but in some ways related topics, mostly related to experimental and theoretical investigations of friction and adhesion of elastomeric materials, are presented. First, an experimental and theoretical study of the interaction between elastic beams and granular media under compressive loading is performed. Buckling loads of beams with different dimensions and boundary conditions within granular media of different depths and grain sizes are measured, and theoretically approximated using the Ritz energy approach, based on the concept of beam on an elastic foundation. Several nondimensional parameters and a scaling law are derived to characterize different interaction regimes between the beams and granular support. The findings from this work is believed to be helpful for improved understanding of interactions between elastic beams and surrounding elastic foundation with applications to piles, oil pipelines, and robotic needle insertion into soft tissues. Second, the role of axial compliance on the friction of extensible strips is investigated. Significant changes were observed in the static and kinetic friction of strips, when the effective axial compliance was changed. The underlying causes of the changes in the frictional response are explained and quantitatively predicted using an extended shear lag model. We believe that this study provides insights into the effect of axial compliance on the frictional response of materials, paving the way for design and optimization of systems where the static and kinetic friction forces play an important role. Third, the effect of normal force and rate on the kinetic friction of two different elastomers, namely acrylic and silicone-based elastomers is evaluated. A custom-built pendulum test setup was used to perform the friction test in dynamic conditions. Two substantially different responses with respect to the change in normal force were observed and the role of different contributions to the frictional response of viscoelastic materials, i.e. bulk hysteresis friction, adhesion friction, and cohesion friction, are discussed. Different scenarios such as modifying the surface by using graphite powder, reducing test velocity, and also performing drop tests to characterize the surface hysteresis of the elastomers, were considered to further explore the origin of frictional responses of the elastomers. This study could improve insights gained from Dynamic Mechanical Analysis (DMA) data when obtaining and interpreting the effect of normal force on kinetic COF of elastomers with potential applications to tires, shoes, etc. where friction plays an important role. Last, a generalized scaling law, based on the classical fracture mechanics approach, is developed to predict the bond strength of adhesive systems. The proposed scaling law, which depends on the rate of change of bond area with compliance, is in apparent discrepancy with the previously reported scaling relationship that depends on the ratio of area to compliance. This distinction can have… Advisors/Committee Members: Dillard, David A. (committeechair), Holmes, Douglas P. (committeechair), Boreyko, Jonathan B. (committee member), Williams, Christopher B. (committee member), Long, Timothy E. (committee member).

Subjects/Keywords: Friction; Adhesion; Elastomeric Materials; Shear Lag Model; Pressure Sensitive Adhesives; Fracture Mechanics

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APA (6^th Edition):

Rezaei Mojdehi, A. (2017). Experimental and Theoretical Studies of Friction and Adhesion of Elastomeric Materials. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/79818

Chicago Manual of Style (16^th Edition):

Rezaei Mojdehi, Ahmad. “Experimental and Theoretical Studies of Friction and Adhesion of Elastomeric Materials.” 2017. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/79818.

MLA Handbook (7^th Edition):

Rezaei Mojdehi, Ahmad. “Experimental and Theoretical Studies of Friction and Adhesion of Elastomeric Materials.” 2017. Web. 13 Apr 2021.

Vancouver:

Rezaei Mojdehi A. Experimental and Theoretical Studies of Friction and Adhesion of Elastomeric Materials. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/79818.

Council of Science Editors:

Rezaei Mojdehi A. Experimental and Theoretical Studies of Friction and Adhesion of Elastomeric Materials. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/79818

Virginia Tech

27. Chartrain, Nicholas. Designing Scaffolds for Directed Cell Response in Tissue Engineering Scaffolds Fabricated by Vat Photopolymerization.

Degree: PhD, Materials Science and Engineering, 2019, Virginia Tech

URL: http://hdl.handle.net/10919/95939

► Vat photopolymerization (VP) is a 3D printing (or additive manufacturing) technology that is capable of fabricating parts with complex geometries with very high resolution. These… (more)

▼ Vat photopolymerization (VP) is a 3D printing (or additive manufacturing) technology that is capable of fabricating parts with complex geometries with very high resolution. These features make VP an attractive option for the fabrication of scaffolds that have applications in tissue engineering. However, there are few printable materials that are biocompatible and allow cells attachment. In addition, those that have been reported cannot be obtained commercially and their synthesis requires substantial resources and expertise. A novel resin composition formulated from commercially available components was developed, characterized, and printed. Scaffolds were printed with high fidelity. The scaffolds had mechanical properties and water contents that suggested they might be suitable for use in tissue engineering. Fibroblast cells were seeded on the scaffolds and successfully adhered and proliferated on the scaffolds. The growth, migration, and differentiation of cells is influenced by the environmental stimuli they experience. In engineered constructs, the scaffold provides many of stimuli. The geometrical features of scaffolds, including how porous they are, the size and shape of their pores, and their overall size are known to affect cell growth. However, scaffolds that have a variety of pore sizes but identical pore shapes, porosities, and other geometric parameters cannot be fabricated with techniques such as porogen leaching and gas foaming. This has resulted in conflicting reports of optimal pore sizes. In this work, several scaffolds with identical pore shapes and porosities but pore sizes ranging from 200 μm to 600 μm were designed and printed using VP. After seeding with cells, scaffolds with large pores (500-600 μm) had a large number of evenly distributed cells while smaller pores resulted in fewer cells that were unevenly distributed. These results suggest that larger pore sizes are most beneficial for culturing fibroblasts. Multi-material tissue scaffolds were fabricated with VP by selectively photocuring two materials into a single part. The scaffolds, which were printed on an unmodified and commercially available VP system, were seeded with cells. The cells were observed to have attached and grown in much larger numbers in certain regions of the scaffolds which corresponded to regions built from a particular resin. By selectively patterning more than one material in the scaffold, cells could be directed towards certain regions and away from others. The ability to control the location of cells suggests that these printing techniques could be used to organize cells and materials in complex ways reminiscent of native tissue. The organization of these cells might then allow the engineered construct to mimic the function of a native tissue. Advisors/Committee Members: Williams, Christopher B. (committeechair), Whittington, Abby R. (committeechair), Long, Timothy E. (committee member), Zheng, Xiaoyu (committee member), Foster, Earl J. (committee member).

Subjects/Keywords: Additive Manufacturing; 3D Printing; Tissue Engineering; Regenerative Medicine; Biomaterials

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Chartrain, N. (2019). Designing Scaffolds for Directed Cell Response in Tissue Engineering Scaffolds Fabricated by Vat Photopolymerization. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/95939

Chicago Manual of Style (16^th Edition):

Chartrain, Nicholas. “Designing Scaffolds for Directed Cell Response in Tissue Engineering Scaffolds Fabricated by Vat Photopolymerization.” 2019. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/95939.

MLA Handbook (7^th Edition):

Chartrain, Nicholas. “Designing Scaffolds for Directed Cell Response in Tissue Engineering Scaffolds Fabricated by Vat Photopolymerization.” 2019. Web. 13 Apr 2021.

Vancouver:

Chartrain N. Designing Scaffolds for Directed Cell Response in Tissue Engineering Scaffolds Fabricated by Vat Photopolymerization. [Internet] [Doctoral dissertation]. Virginia Tech; 2019. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/95939.

Council of Science Editors:

Chartrain N. Designing Scaffolds for Directed Cell Response in Tissue Engineering Scaffolds Fabricated by Vat Photopolymerization. [Doctoral Dissertation]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/95939

Virginia Tech

28. Qian, Chen. Linking the Rheological Behavior to the Processing of Thermotropic Liquid Crystalline Polymers in the Super-cooled State.

Degree: PhD, Chemical Engineering, 2016, Virginia Tech

URL: http://hdl.handle.net/10919/75005

► Thermotropic liquid crystalline polymers (TLCPs) have attracted great interest because of the combination of their promising properties, which includes high stiffness and strength, excellent processability,… (more)

▼ Thermotropic liquid crystalline polymers (TLCPs) have attracted great interest because of the combination of their promising properties, which includes high stiffness and strength, excellent processability, and outstanding chemical resistance. TLCPs exhibit inherently low viscosity relative to many other conventional thermoplastics. The low melt viscosity is detrimental to processes requiring high melt strength, such as extrusion blow molding, film blowing, thermoforming and multilayer coextrusion. Our laboratory has developed a unique method to increase the viscosity of TLCPs by first raising the temperature above the melting point (Tm) to exclude all solid crystalline structure, and then lowering the temperature below Tm to super cool the materials. Additionally, the super-cooling behavior of TLCPs allows them to be blended with other thermoplastics possessing lower processing temperatures. The initial focus of this dissertation is to investigate the processing temperature of a representative TLCP in the super-cooled state, using the methods of small amplitude oscillatory shear (SAOS), the startup of shear flow and differential scanning calorimetry (DSC). The TLCP used in this work is synthesized from 4-hydroxybenzoic acid (HBA), terephthalic acid (TA), hydroquinone (HQ) and hydroquinone derivatives (HQ-derivatives). The TLCP of HBA/TA/HQ/HQ-derivatives has a melting point, Tm, of around 280 °C. Once melted, the TLCP can be cooled 30 °C below the Tm while still maintaining its processability. As the TLCP was cooled to 250 °C, a one order magnitude increase in viscosity was obtained at a shear rate of 0.1 s- 1. Additionally, super cooling the TLCP did not significantly affect the relaxation of shear stress after preshearing. However, the recovery of the transient shear stress in the interrupted shear measurements was suppressed to a great extent in the super-cooled state. The second part of this work is concerned with the extrusion blow molding of polymeric blends containing the TLCP of HBA/TA/HQ/HQ-derivatives and high density polyethylene (HDPE), using a single screw extruder. The blends were processed at a temperature of 260 °C which is 20 °C below Tm of the TLCP such that the thermal degradation of HDPE was minimized. Bottles were successfully produced from the blends containing 10, 20 and 50 wt% TLCP. The TLCP/HDPE blend bottles exhibited an enhanced modulus relative to pure HDPE. However, the improvement in tensile strength was marginal. At 10 and 20 wt% TLCP contents, the TLCP phase existed as platelets, which aligned along the machine direction. A co-continuous morphology was observed for the blend containing 50 wt% TLCP. The preliminary effectiveness of maleic anhydride grafted HDPE (MA-g-HDPE) as a compatibilizer for the TLCP/HDPE system was also studied. The injection molded ternary TLCP/HDPE/MA-g-HDPE blends demonstrated superior mechanical properties over the binary TLCP/HDPE blends, especially in tensile strength. Consequently, it is promising to apply the ternary blends of TLCP/HDPE/MA-g-HDPE in… Advisors/Committee Members: Baird, Donald G. (committeechair), Wilkes, Garth L. (committee member), Martin, Stephen Michael (committee member), Long, Timothy E. (committee member).

Subjects/Keywords: thermotropic liquid crystalline polymer; rheology; super-cooled state

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Qian, C. (2016). Linking the Rheological Behavior to the Processing of Thermotropic Liquid Crystalline Polymers in the Super-cooled State. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/75005

Chicago Manual of Style (16^th Edition):

Qian, Chen. “Linking the Rheological Behavior to the Processing of Thermotropic Liquid Crystalline Polymers in the Super-cooled State.” 2016. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/75005.

MLA Handbook (7^th Edition):

Qian, Chen. “Linking the Rheological Behavior to the Processing of Thermotropic Liquid Crystalline Polymers in the Super-cooled State.” 2016. Web. 13 Apr 2021.

Vancouver:

Qian C. Linking the Rheological Behavior to the Processing of Thermotropic Liquid Crystalline Polymers in the Super-cooled State. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/75005.

Council of Science Editors:

Qian C. Linking the Rheological Behavior to the Processing of Thermotropic Liquid Crystalline Polymers in the Super-cooled State. [Doctoral Dissertation]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/75005

Virginia Tech

29. Inglefield Jr, David Lott. Tailoring Intermolecular Interactions for High-Performance Nanocomposites.

Degree: PhD, Chemistry, 2014, Virginia Tech

URL: http://hdl.handle.net/10919/64411

► Acid oxidation of multi-walled carbon nanotubes (MWCNTs) introduced carboxylic acid sites onto the MWCNT surface, which permitted further functionalization. Derivatization of carboxylic acid sites yielded… (more)

▼ Acid oxidation of multi-walled carbon nanotubes (MWCNTs) introduced carboxylic acid sites onto the MWCNT surface, which permitted further functionalization. Derivatization of carboxylic acid sites yielded amide-amine and amide-urea functionalized MWCNTs from oxidized precursors. Conventional MWCNT characterization techniques including X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Raman spectroscopy supported successful MWCNT functionalization. Incorporation of MWCNTs functionalized with hydrogen bonding groups into a segmented polyurethane matrix led to an increase in mechanical properties at optimized MWCNT loadings, in contrast with non-functionalized MWCNTs that resulted in mechanical property decreases across all loadings. Dynamic mechanical analysis (DMA) demonstrated an increase in the polyurethane-MWCNT composite flow temperature with increasing hydrogen bonding MWCNT incorporation, as opposed to non-functionalized MWCNT composites which displayed no significant change in flow temperature. Variable temperature Fourier transform infrared spectroscopy (VT FT-IR) probed temperature-dependent hydrogen bonding in the polyurethane-MWCNT composites and revealed a significant impact on composite hydrogen bonding interactions upon MWCNT incorporation, which was amplified in composites formed using hydrogen bonding functionalized MWCNTs. Acid oxidation of carbon nanohorns (CNHs) yielded carboxylic acid functionalized CNHs, providing sites for further reaction with histamine to afford histamine-functionalized CNHs (His-CNHs). Raman spectroscopy, XPS and TGA confirmed successful functionalization. Transmission electron microscopy (TEM) demonstrated that His-CNHs efficiently complex quantum dots (QDs) through imidazole-Zn interactions. Combination of His-CNHs, QDs, and a poly(oligo-(ethylene glycol9) methyl ether methacrylate)-block-poly(4-vinyl imidazole) copolymer using an interfacial complexation technique afforded stable ternary nanocomplexes with average hydrodynamic diameters under 100 nm. These ternary nanocomplexes represent promising materials for photothermal cancer theranostics due to their size and stability. The efficient reaction of 2-isocyanatoethyl methacrylate with amines afforded urea-containing methacrylic monomers, where the amine-derived pendant groups determined the polymer Tg. Reversible addition-fragmentation chain-transfer (RAFT) polymerization enabled the synthesis of ABA triblock copolymers with urea-containing methacrylic outer blocks and poly(2-ethylhexyl methacrylate) inner blocks. These ABA triblocks copolymers displayed composition dependent phase-separated morphologies and desirable mechanical properties. The urea-containing polymers efficiently complexed gold nanoparticles through urea-gold interactions. Furthermore, urea-containing methacrylic polymers served as a useful matrix for incorporation of silica-coated upconverting nanoparticles, affording upconverting nanoparticle composite films.The novel ionene monomer… Advisors/Committee Members: Long, Timothy E. (committeechair), Dorn, Harry C. (committee member), Rylander, M Nichole (committee member), Moore, Robert Bowen (committee member).

Subjects/Keywords: polymer nanocomposites; carbon nanomaterials; nanoparticles

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Inglefield Jr, D. L. (2014). Tailoring Intermolecular Interactions for High-Performance Nanocomposites. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/64411

Chicago Manual of Style (16^th Edition):

Inglefield Jr, David Lott. “Tailoring Intermolecular Interactions for High-Performance Nanocomposites.” 2014. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/64411.

MLA Handbook (7^th Edition):

Inglefield Jr, David Lott. “Tailoring Intermolecular Interactions for High-Performance Nanocomposites.” 2014. Web. 13 Apr 2021.

Vancouver:

Inglefield Jr DL. Tailoring Intermolecular Interactions for High-Performance Nanocomposites. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/64411.

Council of Science Editors:

Inglefield Jr DL. Tailoring Intermolecular Interactions for High-Performance Nanocomposites. [Doctoral Dissertation]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/64411

Virginia Tech

30. Arrington, Kyle. Sustainable Polymers Through Creative Design.

Degree: PhD, Chemistry, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/96220

► Plastics have changed the world of materials due to their high durability, low price, low density, and ease of processing. Unfortunately, the majority of plastic… (more)

▼ Plastics have changed the world of materials due to their high durability, low price, low density, and ease of processing. Unfortunately, the majority of plastic goods produced are discarded instead of recycled, leading to a massive accumulation of plastic waste in landfills and natural habitats. To decrease the impact of plastic waste, sustainable materials and synthetic methods are needed. This dissertation focuses on new strategies for developing renewable and degradable polymers with minimal energy input as well as new methods to blend legacy polyolefins with renewable polymers. The first half of the dissertation focuses on synthesizing polymers using light while the second section focuses on combining traditional polyolefins with renewable polymers. Photo-mediated polymerizations are an attractive alternative to traditional thermal polymerizations due to their ease of setup and the spatiotemporal control afforded by light. Using LED lights also affords a synthetic technique that requires little energy input, thus decreasing the overall environmental impact of the material. In this work, coupling LEDs with a trithiocarbonate allowed for the synthesis of many different polymers and topologies. Bottlebrush polymers synthesized with light afforded molar masses in excess of 11 million Da without the oligomerization of the bottlebrush polymers. These bottlebrush polymers were then used to make reversibly crosslinkable adhesives, allowing for a new example of recyclable adhesives. The second half of the dissertation focuses on developing sustainable polymers using ring-opening metathesis polymerization (ROMP) to combine the properties of polyolefins with renewable polymers. First, polyketones synthesized by ROMP were developed for their potential use as photodegradable polymers. This initial study probed the synthesis of different polyketone monomers and the properties of their respective polymers. Next, a photodegradable and biodegradable thermoplastic elastomer (TPE) was synthesized that incorporated a ketone containing polybutadiene (PB) flanked by polylactide (PLA). The thermomechanical properties were controlled based on the relative length of each block while the rate of photodegradation was controlled by the mol% of ketone incorporated into the PB block. Finally, ABA triblock copolymers of cellulose derivatives and polyolefins were developed for their uses as compatibilizers for blends. With the addition of as little as 1 wt% of the ABA triblock copolymer, the respective blends showed large imp Advisors/Committee Members: Matson, John (committeechair), Riffle, Judy S. (committee member), Long, Timothy E. (committee member), Edgar, Kevin J. (committee member).

Subjects/Keywords: compatibilization; polysaccharide; RAFT; ROMP; ROP

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APA (6^th Edition):

Arrington, K. (2018). Sustainable Polymers Through Creative Design. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/96220

Chicago Manual of Style (16^th Edition):

Arrington, Kyle. “Sustainable Polymers Through Creative Design.” 2018. Doctoral Dissertation, Virginia Tech. Accessed April 13, 2021. http://hdl.handle.net/10919/96220.

MLA Handbook (7^th Edition):

Arrington, Kyle. “Sustainable Polymers Through Creative Design.” 2018. Web. 13 Apr 2021.

Vancouver:

Arrington K. Sustainable Polymers Through Creative Design. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10919/96220.

Council of Science Editors:

Arrington K. Sustainable Polymers Through Creative Design. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/96220

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