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

Virginia Tech

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

Degree: MS, Mechanical Engineering, 2012, Virginia Tech

► 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 March 30, 2020. 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. 30 Mar 2020.

Vancouver:

Young TT. Lipid Bilayer Formation in Aqueous Solutions of Ionic Liquids. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2020 Mar 30]. 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

2. Flack, Matthew Alexander. Novel Approaches To The Synthesis of Clicked Block Copolymers.

Degree: MS, Chemistry, 2010, Virginia Tech

URL: http://hdl.handle.net/10919/35801

► Block copolymers are widely used in both the academic and industrial communities due to their unique properties. With the development of living polymerization techniques, the… (more)

Subjects/Keywords: Click chemistry; Polystyrene; Polyisoprene; Block copolymers

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APA (6^th Edition):

Flack, M. A. (2010). Novel Approaches To The Synthesis of Clicked Block Copolymers. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35801

Chicago Manual of Style (16^th Edition):

Flack, Matthew Alexander. “Novel Approaches To The Synthesis of Clicked Block Copolymers.” 2010. Masters Thesis, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/35801.

MLA Handbook (7^th Edition):

Flack, Matthew Alexander. “Novel Approaches To The Synthesis of Clicked Block Copolymers.” 2010. Web. 30 Mar 2020.

Vancouver:

Flack MA. Novel Approaches To The Synthesis of Clicked Block Copolymers. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/35801.

Council of Science Editors:

Flack MA. Novel Approaches To The Synthesis of Clicked Block Copolymers. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/35801

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 March 30, 2020. 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. 30 Mar 2020.

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 2020 Mar 30]. 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. 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 March 30, 2020. http://hdl.handle.net/10919/76896.

MLA Handbook (7^th Edition):

Smith, Colin Frederick. “Jellyfish Inspired Underwater Systems and Technologies.” 2011. Web. 30 Mar 2020.

Vancouver:

Smith CF. Jellyfish Inspired Underwater Systems and Technologies. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2020 Mar 30]. 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

5. 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 March 30, 2020. 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. 30 Mar 2020.

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 2020 Mar 30]. 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

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 March 30, 2020. 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. 30 Mar 2020.

Vancouver:

Nebipasagil A. Chemically and Photochemically Crosslinked Networks and Acid-Functionalized Mwcnt Composites. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2020 Mar 30]. 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. 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 March 30, 2020. 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. 30 Mar 2020.

Vancouver:

Zimmermann KA. Intracellular Transport in Cancer Treatments: Carbon Nanohorns Conjugated to Quantum Dots and Chemotherapeutic Agents. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2020 Mar 30]. 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

8. van der Aa, Eveline Maria. Synthesis and Characterization of Nucleobase-Containing Polyelectrolytes for Gene Delivery.

Degree: MS, Chemistry, 2010, Virginia Tech

URL: http://hdl.handle.net/10919/33008

► Wide literature precedence exists for polymers containing electrostatic interactions and polymers containing hydrogen bonding motifs, however the combination of electrostatic and hydrogen bonding interactions is… (more)

Subjects/Keywords: gene delivery; water-soluble; hydrogen bonding; electrostatic interactions; nucleobase; polyelectrolyte

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APA (6^th Edition):

van der Aa, E. M. (2010). Synthesis and Characterization of Nucleobase-Containing Polyelectrolytes for Gene Delivery. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33008

Chicago Manual of Style (16^th Edition):

van der Aa, Eveline Maria. “Synthesis and Characterization of Nucleobase-Containing Polyelectrolytes for Gene Delivery.” 2010. Masters Thesis, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/33008.

MLA Handbook (7^th Edition):

van der Aa, Eveline Maria. “Synthesis and Characterization of Nucleobase-Containing Polyelectrolytes for Gene Delivery.” 2010. Web. 30 Mar 2020.

Vancouver:

van der Aa EM. Synthesis and Characterization of Nucleobase-Containing Polyelectrolytes for Gene Delivery. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/33008.

Council of Science Editors:

van der Aa EM. Synthesis and Characterization of Nucleobase-Containing Polyelectrolytes for Gene Delivery. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/33008

Virginia Tech

9. 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 March 30, 2020. 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. 30 Mar 2020.

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 2020 Mar 30]. 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

10. 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 March 30, 2020. 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. 30 Mar 2020.

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 2020 Mar 30]. 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

11. 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 March 30, 2020. http://hdl.handle.net/10919/51115.

MLA Handbook (7^th Edition):

Schultz, Alison. “Functional Block Copolymers via Anionic Polymerization for Electroactive Membranes.” 2013. Web. 30 Mar 2020.

Vancouver:

Schultz A. Functional Block Copolymers via Anionic Polymerization for Electroactive Membranes. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2020 Mar 30]. 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

12. Chen, Xi. Designing Acrylic Block Copolymers with Multiple Hydrogen Bonding or Multiple Ionic Bonding.

Degree: MS, Chemistry, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/84961

► The dynamic characteristics of hydrogen and ionic bonding contributes to the reversible properties of acrylic polymers, opening new avenues for designing materials with mechanical strength… (more)

▼ The dynamic characteristics of hydrogen and ionic bonding contributes to the reversible properties of acrylic polymers, opening new avenues for designing materials with mechanical strength and processability. These non-covalent interactions function as physical crosslinks, which provide enhanced structural and mechanical integrity to acrylic block copolymers. The strong hydrogen bonding or ionic interaction also directs self-assembly to hierarchical microstructures, which enables many applications including thermoplastic elastomers and energy storage devices. Inspired by complementary hydrogen bonding interactions between nucleobase pairs in DNA, a series of bioinspired nucleobase-acrylate monomers such as adenine acrylate (AdA), thymine acrylate (ThA), cytosine acrylate (CyA) were designed, whose synthesis were afforded by aza-Michael addition. Among those nucleobases, cytosine arises as a unique category. It is not only able to self-associate via weak hydrogen bonds, but also forms quadruple hydrogen-bond bearing units (ureido-cytosine) when functionalized with isocyanates. Reversible addition-fragmentation chain transfer polymerization (RAFT) yielded acrylic ABA triblock copolymers with CyA external hard blocks. A subsequent post-functionalization using hexyl-isocyanate generated the corresponding ureido-cytosine acrylate(UCyA)-containing triblock copolymers. The self-complementary quadruple hydrogen bonding in the UCyA polymers achieved a broader service iii temperature window, while the alkyl chain ends of UCyA units allowed tunability of the mechanical strength to apply as thermoplastic elastomers. In addition, quadruple hydrogen bonding induced stronger propensity of self-assembly and denser packing of the polymers, which contributed to a well-defined ordered morphology and enhanced resistance to moisture uptake. A facile 2-step synthesis provided doubly-charged styrenic DABCO salt monomer(VBDC18BrCl) containing an octadecyl tail. RAFT polymerization allowed the preparation of DABCO ABA block copolymers with defined molecular weights and low polydispersity. Thermal analysis revealed a melting transition of the VBDC18BrCl block copolymer resulting from the side-chain crystallization of the long alkyl tail. Systematic mechanical comparisons between DABCO salt-containing copolymers and the corresponding singly-charged polymer controls demonstrated superior mechanical properties attributable to a stronger ionic interaction between the doubly-charged groups. Morphological characterizations revealed a well-ordered lamellar microstructure and a unique three-phase morphology of the DABCO block copolymers, which involve a soft phase, a hard phase, and an ionic aggregates domain dispersed within the hard domain. Advisors/Committee Members: Long, Timothy E. (committeechair), Edgar, Kevin J. (committee member), Moore, Robert Bowen (committee member).

Subjects/Keywords: Block copolymer; hydrogen bonding; ionic interaction; nucleobase; DABCO salt; mechanical property; self-assembly; 3-D printing

…Long* Department of Chemistry, Macromolecules Innovation Institute (MII), Virginia… …Tech, Blacksburg, VA, 24061 2.1 Abstract RAFT polymerization is a versatile and facile…

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APA (6^th Edition):

Chen, X. (2018). Designing Acrylic Block Copolymers with Multiple Hydrogen Bonding or Multiple Ionic Bonding. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/84961

Chicago Manual of Style (16^th Edition):

Chen, Xi. “Designing Acrylic Block Copolymers with Multiple Hydrogen Bonding or Multiple Ionic Bonding.” 2018. Masters Thesis, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/84961.

MLA Handbook (7^th Edition):

Chen, Xi. “Designing Acrylic Block Copolymers with Multiple Hydrogen Bonding or Multiple Ionic Bonding.” 2018. Web. 30 Mar 2020.

Vancouver:

Chen X. Designing Acrylic Block Copolymers with Multiple Hydrogen Bonding or Multiple Ionic Bonding. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/84961.

Council of Science Editors:

Chen X. Designing Acrylic Block Copolymers with Multiple Hydrogen Bonding or Multiple Ionic Bonding. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/84961

Virginia Tech

13. 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, Sam Richard (committee member), Heflin, James Randy (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 March 30, 2020. http://hdl.handle.net/10919/82226.

MLA Handbook (7^th Edition):

Margaretta, Evan David. “Imparting Functionality to Macromolecules for Selective Stimulus Response.” 2016. Web. 30 Mar 2020.

Vancouver:

Margaretta ED. Imparting Functionality to Macromolecules for Selective Stimulus Response. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2020 Mar 30]. 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

Virginia Tech

14. June, Stephen Matthew. Step-Growth Polymerization Towards the Design of Polymers: Assembly and Disassembly of Macromolecules.

Degree: PhD, Chemistry, 2012, Virginia Tech

URL: http://hdl.handle.net/10919/37619

► Step-growth polymerization provided an effective method for the preparation of several high performance polymers. Step-growth polymerization was used for syntheses of poly(siloxane imides), polyesters, poly(triazole… (more)

▼ Step-growth polymerization provided an effective method for the preparation of several high performance polymers. Step-growth polymerization was used for syntheses of poly(siloxane imides), polyesters, poly(triazole esters), poly(triazole ether esters), and epoxy networks. Each of these polymeric systems exhibited novel structures, and either photoreactive capabilities, or high performance properties. There is an increasing trend towards the development of photoactive adhesives. In particular these polymers are often used in flip bonding, lithography, stimuli responsive polymers, drug delivery, and reversible adhesives. The ability to tailor polymer properties carefully with exposure to light allows for very unique stimuli responsive properties for many applications. This dissertation primarily investigates photoreactive polymers for reversible adhesion for use in the fabrication of microelectronic devices. In particular cyclobutane diimide functionality within polyimides and poly(siloxane imides) and o-nitro benzyl ester functionality within polyesters acted effectively as chromophores to this end. Thermal solution imidization allowed for the effective synthesis of polyimides and poly(siloxane imides). 1,2,3,4-Cyclobutane tetracarboxylic dianhydride acted as the chromophore within the polymer backbone. The polyimides obtained exhibited dispersibility only in dipolar, aprotic, high boiling solvents such as DMAc or NMP. The obtained poly(siloxane imides) demonstrated enhanced dispersibility in lower boiling organic solvents such as THF and CHCl3. Dynamic mechanical analysis and tensile testing effectively measure the mechanical properties of the photoactive poly(siloxane imides) and confirmed elastomeric properties. Atomic force microscopy confirmed microphase separation of the photoactive poly(siloxane imides). 1H NMR spectroscopy confirmed formation of maleimide peaks upon exposure to narrow band UV light with a wavelength of 254 nm. This suggested photo-cleavage of the cyclobutane diimide units within the polymer backbone. Melt transesterification offered a facile method for the synthesis of o-nitro benzyl ester-containing polyesters. 1H NMR spectroscopy confirmed the structures of the photoactive polyesters and size exclusion chromatography confirmed reasonable molecular weights and polydispersities of the obtained samples. 1H NMR spectroscopy also demonstrated a decrease in the integration of the resonance corresponding to the o-nitro benzyl ester functionality relative to the photo-stable m-nitro benzyl ester functionality upon exposure to high-intensity UV light, suggesting photo-degradation of the adhesive. ASTM wedge testing verified a decrease in fracture energy of the adhesive upon UV exposure, comparable to the decrease in fracture energy of a commercial hot-melt adhesive upon an increase in temperature. Click chemistry was used to synthesize polyesters and segmented block copolyesters. Triazole-containing homopolyesters exhibited a marked increase (~40 Â°C) in Tg, relative to… Advisors/Committee Members: Long, Timothy E. (committeechair), Moore, Robert B. (committee member), Davis, Richey M. (committee member), Turner, S. Richard (committee member).

Subjects/Keywords: Polycondensation; Polyaddition; Step-Growth Polymers; Epoxy Networks; Microbial Fuel Cells; Photo-active Polymers; Poly(siloxane imides); Polyesters; â Clickâ Chemistry; Stimuli Responsive Polymers; Bisphenol-A; BPA

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APA (6^th Edition):

June, S. M. (2012). Step-Growth Polymerization Towards the Design of Polymers: Assembly and Disassembly of Macromolecules. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/37619

Chicago Manual of Style (16^th Edition):

June, Stephen Matthew. “Step-Growth Polymerization Towards the Design of Polymers: Assembly and Disassembly of Macromolecules.” 2012. Doctoral Dissertation, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/37619.

MLA Handbook (7^th Edition):

June, Stephen Matthew. “Step-Growth Polymerization Towards the Design of Polymers: Assembly and Disassembly of Macromolecules.” 2012. Web. 30 Mar 2020.

Vancouver:

June SM. Step-Growth Polymerization Towards the Design of Polymers: Assembly and Disassembly of Macromolecules. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/37619.

Council of Science Editors:

June SM. Step-Growth Polymerization Towards the Design of Polymers: Assembly and Disassembly of Macromolecules. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/37619

Virginia Tech

15. 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 (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 March 30, 2020. http://hdl.handle.net/10919/64411.

MLA Handbook (7^th Edition):

Inglefield Jr, David Lott. “Tailoring Intermolecular Interactions for High-Performance Nanocomposites.” 2014. Web. 30 Mar 2020.

Vancouver:

Inglefield Jr DL. Tailoring Intermolecular Interactions for High-Performance Nanocomposites. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2020 Mar 30]. 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

16. 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 March 30, 2020. 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. 30 Mar 2020.

Vancouver:

Savage A. Synthesis and Solution Properties of Semi-rigid Polyelectrolytes and Polyampholytes. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2020 Mar 30]. 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

17. Buckwalter, Daniel James. Non-covalent Intermolecular Interactions in Polymer Design: Segmented Copolymers to Non-viral Gene Delivery Vectors.

Degree: PhD, Chemistry, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/50926

► Non-covalent intermolecular interactions play a large role in determining the properties of a given system, from segmented copolymers to interactions of functionalized polymers with non-viral… (more)

▼ Non-covalent intermolecular interactions play a large role in determining the properties of a given system, from segmented copolymers to interactions of functionalized polymers with non-viral nucleic acids delivery vehicles. The ability to control the intermolecular interactions of a given system allow for tailoring of that system to yield a desired outcome, whether it is a copolymers mechanical properties or the colloidal stability of a pDNA-delivery vector complex. Each chemical system relies on one or more types of intermolecular interaction such as hydrogen bonding, cooperative À-À stacking, electrostatic interactions, van der waals forces, metal-ligand coordination, or hydrophobic/solvophobic effects. The following research describes the tailoring of specific intermolecular interactions aimed at altering the physical properties of segmented copolymers and non-viral gene delivery vectors. Amide containing segmented copolymers relies heavily on hydrogen bonding intermolecular interactions for physical crosslinking to impart the necessary microphase separated morphology responsible for a copolymers physical properties. Amide containing hard segments are composed of various chemical structures from crystalline aramids to amorphous alkyl amides with each structure possessing unique intermolecular interactions. Variations to either of the copolymer segments alters the copolymers physical properties allowing for tuning of a copolymers properties for a particular application. The synthetic strategies, structure-property relationships, and physical properties of amide containing segmented copolymers are thoroughly reported in the literature. Each class of segmented copolymer that contain amide hydrogen bonding groups exhibits a wide range of tunable properties desirable for many applications. The segmented copolymers discussed here include poly(ether-block-amide)s, poly(ether ester amide)s, poly(ester amide)s, poly(oxamide)s, PDMS polyamides, and polyamides containing urethane, urea, or imide groups. The structure-property relationships (SPR) of poly(oxamide) segmented copolymers is not well understood with only one report currently found in literature. The effects of oxamide spacing in the hard segment and molecular weight of the soft segments in PDMS poly(oxamide) segmented copolymers demonstrated the changes in physical properties associated with minor structural variations. The optically clear PDMS poly(oxamide) copolymers possessed good mechanical properties after bulk polymerization of ethyl oxalate terminated PDMS oligomers with alkyl diamines or varied length. FTIR spectroscopy experiments revealed an ordered hydrogen bonding carbonyl stretching band for each copolymer and as the spacing between oxamide groups increased, the temperature at which the hard segment order was disrupted decreased. The increased spacing between oxamide groups also led to a decrease in the flow temperature observed with dynamic mechanical analysis. Copolymer tensile properties decrease with increased oxamide spacing as… Advisors/Committee Members: Long, Timothy E. (committeechair), Tanko, James M. (committee member), Moore, Robert Bowen (committee member), Matson, John (committee member).

Subjects/Keywords: poly(amide); oxamide; segmented copolymer; trioxamide; poly(urea); poly(urea oxamide); non-viral gene delivery; click cluster; A^ oyæ7ÝkX•Q•••åé•'••é(ÈY•• %í•4•

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APA (6^th Edition):

Buckwalter, D. J. (2013). Non-covalent Intermolecular Interactions in Polymer Design: Segmented Copolymers to Non-viral Gene Delivery Vectors. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50926

Chicago Manual of Style (16^th Edition):

Buckwalter, Daniel James. “Non-covalent Intermolecular Interactions in Polymer Design: Segmented Copolymers to Non-viral Gene Delivery Vectors.” 2013. Doctoral Dissertation, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/50926.

MLA Handbook (7^th Edition):

Buckwalter, Daniel James. “Non-covalent Intermolecular Interactions in Polymer Design: Segmented Copolymers to Non-viral Gene Delivery Vectors.” 2013. Web. 30 Mar 2020.

Vancouver:

Buckwalter DJ. Non-covalent Intermolecular Interactions in Polymer Design: Segmented Copolymers to Non-viral Gene Delivery Vectors. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/50926.

Council of Science Editors:

Buckwalter DJ. Non-covalent Intermolecular Interactions in Polymer Design: Segmented Copolymers to Non-viral Gene Delivery Vectors. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/50926

Virginia Tech

18. Mitroka, Susan M. Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene.

Degree: PhD, Chemistry, 2010, Virginia Tech

URL: http://hdl.handle.net/10919/77137

► Oxidative processes are linked to a number of major disease states as well as the breakdown of many materials. Of particular importance are reactive oxygen… (more)

▼ Oxidative processes are linked to a number of major disease states as well as the breakdown of many materials. Of particular importance are reactive oxygen species (ROS), as they are known to be endogenously produced in biological systems as well as exogenously produced through a variety of different means. In hopes of better understanding what controls the behavior of ROS, researchers have studied radical chemistry on a fundamental level. Fundamental knowledge of what contributes to oxidative processes can be extrapolated to more complex biological or macromolecular systems. Fundamental concepts and applied data (i.e. interaction of ROS with polymers, biomolecules, etc.) are critical to understanding the reactivity of ROS. A detailed review of the literature, focusing primarily on the hydroxyl radical (HO•) and hydrogen atom (H•) abstraction reactions, is presented in Chapter 1. Also reviewed herein is the literature concerning high density polyethylene (HDPE) degradation. Exposure to treated water systems is known to greatly reduce the lifetime of HDPE pipe. While there is no consensus on what leads to HDPE breakdown, evidence suggests oxidative processes are at play. The research which follows in Chapter 2 focuses on the reactivity of the hydroxyl radical and how it is controlled by its environment. The HO• has been thought to react instantaneously, approaching the diffusion controlled rate and showing little to no selectivity. Both experimental and calculational evidence suggest that some of the previous assumptions regarding hydroxyl radical reactivity are wrong and that it is decidedly less reactive in an aprotic polar solvent than in aqueous solution. These findings are explained on the basis of a polarized transition state that can be stabilized via the hydrogen bonding afforded by water. Experimental and calculational evidence also suggest that the degree of polarization in the transition state will determine the magnitude of this solvent effect. Chapter 3 discusses the results of HDPE degradation studies. While HDPE is an extremely stable polymer, exposure to chlorinated aqueous conditions severely reduces the lifetime of HDPE pipes. While much research exists detailing the mechanical breakdown and failure of these pipes under said conditions, a gap still exists in defining the species responsible or mechanism for this degradation. Experimental evidence put forth in this dissertation suggests that this is due to an auto-oxidative process initiated by free radicals in the chlorinated aqueous solution and propagated through singlet oxygen from the environment. A mechanism for HDPE degradation is proposed and discussed. Additionally two small molecules, 2,3-dichloro-2-methylbutane and 3-chloro-1,1-di-methylpropanol, have been suggested as HDPE byproducts. While the mechanism of formation for these products is still elusive, evidence concerning their identification and production in HDPE and PE oligomers is discussed. Finally, Chapter 4 deals with concluding remarks of the aforementioned work. Future work… Advisors/Committee Members: Tanko, James M. (committeechair), Carlier, Paul R. (committee member), Long, Timothy E. (committee member), Dietrich, Andrea M. (committee member), Troya, Diego (committee member).

Subjects/Keywords: hydroxyl radical; hydrogen atom transfer; polarized transition state; oxidation; auto oxidation; high density polyethylene; accelerated aging

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APA (6^th Edition):

Mitroka, S. M. (2010). Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77137

Chicago Manual of Style (16^th Edition):

Mitroka, Susan M. “Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene.” 2010. Doctoral Dissertation, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/77137.

MLA Handbook (7^th Edition):

Mitroka, Susan M. “Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene.” 2010. Web. 30 Mar 2020.

Vancouver:

Mitroka SM. Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene. [Internet] [Doctoral dissertation]. Virginia Tech; 2010. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/77137.

Council of Science Editors:

Mitroka SM. Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene. [Doctoral Dissertation]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/77137

Virginia Tech

19. Wilmsmeyer, Kyle Gregory. Nuclear magnetic resonance and rheo-NMR investigations of wormlike micelles, rheology modifiers, and ion-conducting polymers.

Degree: PhD, Chemistry, 2012, Virginia Tech

URL: http://hdl.handle.net/10919/77239

► Investigation and characterization of polymeric materials are necessary to obtain in-depth understanding of their behavior and properties, which can fuel further development. To illuminate these… (more)

▼ Investigation and characterization of polymeric materials are necessary to obtain in-depth understanding of their behavior and properties, which can fuel further development. To illuminate these molecular properties and their coupling to macroscopic behavior, we have performed nuclear magnetic resonance (NMR) studies on a variety of chemical systems. In addition to versatile "traditional" NMR measurements, we took advantage of specialized techniques, such as "rheo-NMR," 2H NMR, and NMR self-diffusion experiments to analyze alignment, orientational order, elaborate rheological behavior, and ion transport in polymer films and complex fluids. We employed self-diffusion and quadrupolar deuterium NMR methods to water-swollen channels in Nafion ionomer films commonly used in fuel cells and actuators. We also correlated water uptake and anisotropic diffusion with differing degrees and types of alignment in Nafion films based on membrane processing methods. Further, we made quantitative measurements of bulk channel alignment in Nafion membranes and determined anisotropic properties such as the biaxiality parameter using these methods. Additionally, our studies made the first direct comparison of directional transport (diffusion) with quantitative orientational order measurements for ionomer membranes. These results lend insight to the importance of water content in ionomer device performance, and showed that increased control over the direction and extent of orientational order of the hydrophilic channels could lead to improved materials design. We used the same techniques, with the addition of "rheo-NMR" and solution rheology measurements, to study the complex rheological behavior of cetyltrimethylammonium bromide wormlike micelle solutions, which behave as nematic liquid crystals at sufficiently high concentration. Amphiphilic solutions of this type are used in myriad applications, from fracturing fluids in oil fields to personal care products. We investigated the phase behavior and dynamics of shear and magnetic field alignment, and made the first observations of a novel bistable shear-activated phase in these solutions. Our first reports of the complex Leslie-Ericksen viscoelastic parameters in wormlike micelles and measurements of diffusion anisotropy show the potential for increased control and understanding of materials used in tissue engineering, oil extraction, personal care products, and advanced lubricants. Advisors/Committee Members: Madsen, Louis A. (committeechair), Marand, Hervé L. (committee member), Long, Timothy E. (committee member), Dorn, Harry C. (committee member).

Subjects/Keywords: surfactant; self-diffusion; rheo-NMR; Nafion; wormlike micelle; viscoelasticity; rheology; nuclear magnetic resonance

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APA (6^th Edition):

Wilmsmeyer, K. G. (2012). Nuclear magnetic resonance and rheo-NMR investigations of wormlike micelles, rheology modifiers, and ion-conducting polymers. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77239

Chicago Manual of Style (16^th Edition):

Wilmsmeyer, Kyle Gregory. “Nuclear magnetic resonance and rheo-NMR investigations of wormlike micelles, rheology modifiers, and ion-conducting polymers.” 2012. Doctoral Dissertation, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/77239.

MLA Handbook (7^th Edition):

Wilmsmeyer, Kyle Gregory. “Nuclear magnetic resonance and rheo-NMR investigations of wormlike micelles, rheology modifiers, and ion-conducting polymers.” 2012. Web. 30 Mar 2020.

Vancouver:

Wilmsmeyer KG. Nuclear magnetic resonance and rheo-NMR investigations of wormlike micelles, rheology modifiers, and ion-conducting polymers. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/77239.

Council of Science Editors:

Wilmsmeyer KG. Nuclear magnetic resonance and rheo-NMR investigations of wormlike micelles, rheology modifiers, and ion-conducting polymers. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/77239

Virginia Tech

20. 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 (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 March 30, 2020. 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. 30 Mar 2020.

Vancouver:

Fox SC. Regioselective Synthesis of Novel Cellulose Derivatives for Drug Delivery. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2020 Mar 30]. 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

21. Carter, Nathan Andrew. Design Strategies for Dynamic Self-assembled Protein Materials.

Degree: PhD, Chemistry, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/93207

► Structures in nature exhibit unique and complex architectures whose order propagates from nano- (10-9 m) to macro-scales (mm to m). These structures give rise to… (more)

▼ Structures in nature exhibit unique and complex architectures whose order propagates from nano- (10-9 m) to macro-scales (mm to m). These structures give rise to a rich diversity of adaptive function that allows for life in all environments on Earth. This complex functionality has driven research into bio-inspired materials where scientists investigate the complex relationship between sequence, structure and function of these materials. A good illustrative example of the effect that hierarchical structure can have is a brick wall. Bricks are laid so that the layer on top is shifted in either direction by half of a brick. This alternating pattern is what gives the wall its strength. If a crack occurs in the mortar, it will only propagate until it hits a boundary (a neighboring brick). Designing nanostructures can have similar effects on materials we use every day. Some of the most prevalent are adhesives that mimic the structures on gecko feet, which allow them to stick to any surface. This work presents bottom-up design strategies for self-assembling protein materials whose hierarchical structure may prove useful in a variety of applications in soft-robotics and energy storage. Proteins are a useful class of molecules, because they contain a level of structural complexity beyond that of synthetic materials. They are an inherently 'green' material feedstock; made in a lab using microbes like E. coli. Additionally, with the ease and availability of genetic engineering techniques we can easily modify the structure. This is especially true for the class of proteins, repeat proteins, which are the focus of this manuscript. Repeat proteins comprise small repeated sequences which are structurally independent from each other and can be strung together to create open, extended architectures. Here we explore the self-assembly emergent properties of the consensus tetratricopeptide repeat (CTPR18) . We show that this protein assembles into highly ordered 1D and 2D arrays that are shape tunable based the molecular environment (solvents, charge, etc). These nanomaterials may prove useful as molecular recognition scaffolds. We further explore the hierarchical self-assembled films of CTPR18. These films form highly oriented lamellar structures that seemingly propagate the entire length of the films. These lamellae directly affect the materials mechanical properties. Accordingly, by changing the film casting conditions, we can impart a structural gradient in the film, which proves useful in tuning the water-induced bending motion of these films. Herein, we show the ability to change the speed and directionality of actuation by simply changing the underlying film morphology. Lastly, we show that these films are electroresponsive as well, owing this function to ion transport through the inherently charged character of CTPR18. These dual responsive materials may prove useful in soft robotics. Additionally we are beginning investigations into the usefulness of CTPR18 films as alternate materials for ion-transport materials like those… Advisors/Committee Members: Grove, Tijana (committeechair), Long, Timothy E. (committee member), Esker, Alan R. (committee member), Goldstein, Aaron S. (committee member).

Subjects/Keywords: Biomaterials; self-assembly; protein materials

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APA (6^th Edition):

Carter, N. A. (2018). Design Strategies for Dynamic Self-assembled Protein Materials. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/93207

Chicago Manual of Style (16^th Edition):

Carter, Nathan Andrew. “Design Strategies for Dynamic Self-assembled Protein Materials.” 2018. Doctoral Dissertation, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/93207.

MLA Handbook (7^th Edition):

Carter, Nathan Andrew. “Design Strategies for Dynamic Self-assembled Protein Materials.” 2018. Web. 30 Mar 2020.

Vancouver:

Carter NA. Design Strategies for Dynamic Self-assembled Protein Materials. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/93207.

Council of Science Editors:

Carter NA. Design Strategies for Dynamic Self-assembled Protein Materials. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/93207

22. Beach, Jeremy. Preparation and Electrochemical Testing of Flexible Carbon Nanofiber Electrodes from Electrospinning.

Degree: PhD, Chemistry, 2017, Virginia Tech

URL: http://hdl.handle.net/10919/89627

► The purpose of this research project was to determine the processing conditions necessary for preparing flexible carbon nanofiber electrodes by electrospinning and to explore various… (more)

▼ The purpose of this research project was to determine the processing conditions necessary for preparing flexible carbon nanofiber electrodes by electrospinning and to explore various applications for those electrodes. It was found that by varying only the relative humidity while electrospinning a poly(acrylonitrile) precursor, fragile or flexible freestanding carbon nanofiber electrodes were prepared. The relative humidity during electrospinning controlled the fiber diameter, the bulk porosity of the material, and flexibility of the final carbon electrode. Higher porosity mats electrospun in a high relative humidity environment prevented fiber sintering, which if not minimized, resulted in non-flexible carbon electrodes. Both flexible and fragile electrodes were freestanding, binderless, and collectorless. Additionally, they required no further processing before use and were 100 wt.% active material. When cycled galvanostatically as a lithium ion battery anode, the flexible electrode exhibited a specific capacity of 379 mAH g-1 at the 100th cycle and capacity retention was 97.4% relative to the fifth cycle. When applied as an active material support electrode for lithium ion battery cathodes, the carbon support was successfully utilized with both micron and nano structured active material and cycled for 100 cycles with limited capacity loss. The same electrodes were also found to be a viable replacement for Pt electrode based actuators/artificial muscles. However, this application requires much further research to understand better the required processing and effects of the physical properties of the electrode on actuator performance. In addition to this, the flexible electrodes have a wide variety of other potential applications including, electrochemical storage and conversion devices, chemical sensing, and filtration. The focus of this work was electrochemical storage and conversion devices in the form of lithium ion battery anodes and cathodes as well as ionic polymer composite actuators. Advisors/Committee Members: Moore, Robert Bowen (committeechair), Ellis, Michael W. (committee member), Esker, Alan R. (committee member), Long, Timothy E. (committee member).

Subjects/Keywords: Electrospinning; Nano; Carbon; Electrode; Batteries

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APA (6^th Edition):

Beach, J. (2017). Preparation and Electrochemical Testing of Flexible Carbon Nanofiber Electrodes from Electrospinning. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/89627

Chicago Manual of Style (16^th Edition):

Beach, Jeremy. “Preparation and Electrochemical Testing of Flexible Carbon Nanofiber Electrodes from Electrospinning.” 2017. Doctoral Dissertation, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/89627.

MLA Handbook (7^th Edition):

Beach, Jeremy. “Preparation and Electrochemical Testing of Flexible Carbon Nanofiber Electrodes from Electrospinning.” 2017. Web. 30 Mar 2020.

Vancouver:

Beach J. Preparation and Electrochemical Testing of Flexible Carbon Nanofiber Electrodes from Electrospinning. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/89627.

Council of Science Editors:

Beach J. Preparation and Electrochemical Testing of Flexible Carbon Nanofiber Electrodes from Electrospinning. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/89627

Virginia Tech

23. 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, Sam 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 (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 March 30, 2020. 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. 30 Mar 2020.

Vancouver:

Edling HE. Synthesis and Structure-Property Relationships of Polyesters Containing Rigid Aromatic Structures. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2020 Mar 30]. 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

24. 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, Sam 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 · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

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 March 30, 2020. 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. 30 Mar 2020.

Vancouver:

Tamami M. Synthesis and characterization of ammonium ionenes containing hydrogen bonding functionalities. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2020 Mar 30]. 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

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

Degree: PhD, Learning Sciences and Technologies, 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, Sam 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 March 30, 2020. http://hdl.handle.net/10919/71383.

MLA Handbook (7^th Edition):

Meng, Xiangtao. “Chemical Modification of Cellulose Esters for Oral Drug Delivery.” 2016. Web. 30 Mar 2020.

Vancouver:

Meng X. Chemical Modification of Cellulose Esters for Oral Drug Delivery. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2020 Mar 30]. 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

26. 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, Sam 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 March 30, 2020. 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. 30 Mar 2020.

Vancouver:

Zhang K. Bio-inspired Design and Self-Assembly of Nucleobase- and Ion-Containing Polymers. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2020 Mar 30]. 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

27. 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, Sam 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 March 30, 2020. 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. 30 Mar 2020.

Vancouver:

Nelson AM. Design of Functional Polyesters for Electronic and Biological Applications. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2020 Mar 30]. 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

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 March 30, 2020. 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. 30 Mar 2020.

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 2020 Mar 30]. 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

29. Radzinski, Scott Charles. Synthesis of Bottlebrush Polymers Using the Grafting-Through and Transfer-To Methods.

Degree: PhD, Chemistry, 2017, Virginia Tech

URL: http://hdl.handle.net/10919/77574

► Bottlebrush polymers are interesting topologies that have become increasingly relevant in various applications including rheology modifiers, super-soft elastomers, photonic crystals, anti-fouling coatings, the in vivo… (more)

▼ Bottlebrush polymers are interesting topologies that have become increasingly relevant in various applications including rheology modifiers, super-soft elastomers, photonic crystals, anti-fouling coatings, the in vivo delivery of therapeutic agents, and as promising substrates in lithographic printing. These macromolecules are comprised of numerous polymeric side-chains densely grafted to a polymer backbone. The densely grafted nature of bottlebrush polymers results in steric repulsion between neighboring polymer chains, forcing these macromolecules to adopt a chain-extended conformation. Although these remarkable macromolecules have a many different applications, the transformative potential of the bottlebrush polymer topology has not been realized because the synthesis of high molecular weight bottlebrush polymers is challenging. This dissertation focusses on improving the synthesis of these large macromolecules using the grafting-through strategy in the first section and the transfer-to strategy in the second section. For the first time the effect of anchor group chemistry—the configuration of atoms linking the polymer to a polymerizable norbornene—was studied on the kinetics of ring-opening metathesis polymerization (ROMP) of macromonomers (MMs) initiated by Grubbs 3rd generation catalyst. A variance in the rate of propagation of >4-fold between similar MMs with different anchor groups was observed. This phenomenon was conserved across all MMs tested, regardless of solvent, molecular weight (MW), or repeat unit identity. Experimental and computational studies indicated that the rate differences likely resulted from a combination of varying steric demands and electronic structure among the different anchor groups. This new insight will allow others to achieve high MM conversion and prepare pure, high MW bottlebrush polymers by ROMP grafting-through. The second section of this dissertation deals with a little studied bottlebrush synthesis technique called the transfer-to method. This method is a hybrid of the grafting-from and grafting-to approaches in which the growing polymer side chains detach from the backbone, propagate freely in solution, and then reattach to the backbone in a chain transfer step. Several parameters were investigated to determine optimal conditions for this process. This study provides for the first time a guide to use the transfer-to method to produce high purity bottlebrush polymers with controllable backbone and side chain length. Advisors/Committee Members: Matson, John (committeechair), Liu, Guoliang (committee member), Long, Timothy E. (committee member), Gibson, Harry W. (committee member).

Subjects/Keywords: Comb polymer; Controlled radical polymerization; Z-RAFT

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APA (6^th Edition):

Radzinski, S. C. (2017). Synthesis of Bottlebrush Polymers Using the Grafting-Through and Transfer-To Methods. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77574

Chicago Manual of Style (16^th Edition):

Radzinski, Scott Charles. “Synthesis of Bottlebrush Polymers Using the Grafting-Through and Transfer-To Methods.” 2017. Doctoral Dissertation, Virginia Tech. Accessed March 30, 2020. http://hdl.handle.net/10919/77574.

MLA Handbook (7^th Edition):

Radzinski, Scott Charles. “Synthesis of Bottlebrush Polymers Using the Grafting-Through and Transfer-To Methods.” 2017. Web. 30 Mar 2020.

Vancouver:

Radzinski SC. Synthesis of Bottlebrush Polymers Using the Grafting-Through and Transfer-To Methods. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2020 Mar 30]. Available from: http://hdl.handle.net/10919/77574.

Council of Science Editors:

Radzinski SC. Synthesis of Bottlebrush Polymers Using the Grafting-Through and Transfer-To Methods. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/77574

Virginia Tech

30. 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 (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 March 30, 2020. 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. 30 Mar 2020.

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 2020 Mar 30]. 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

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