+publisher:"Virginia Tech" +contributor:("Esker, Alan R.")

Virginia Tech

1. Yang, Sha. Crystallization, Melting Behavior, Physical Properties, and Physical Aging of Ethylene/1-Octene Copolymers.

Degree: MS, Chemistry, 2011, Virginia Tech

URL: http://hdl.handle.net/10919/72985

► The time dependence of the physical properties of ethylene/1-octene (EO)-copolymers after primary crystallization is investigated by calorimetry, density, and creep measurements. The temporal evolution of… (more)

Subjects/Keywords: crystallization; ethylene/1-octene copolymers; melting; physical aging

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APA (6^th Edition):

Yang, S. (2011). Crystallization, Melting Behavior, Physical Properties, and Physical Aging of Ethylene/1-Octene Copolymers. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/72985

Chicago Manual of Style (16^th Edition):

Yang, Sha. “Crystallization, Melting Behavior, Physical Properties, and Physical Aging of Ethylene/1-Octene Copolymers.” 2011. Masters Thesis, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/72985.

MLA Handbook (7^th Edition):

Yang, Sha. “Crystallization, Melting Behavior, Physical Properties, and Physical Aging of Ethylene/1-Octene Copolymers.” 2011. Web. 22 Oct 2019.

Vancouver:

Yang S. Crystallization, Melting Behavior, Physical Properties, and Physical Aging of Ethylene/1-Octene Copolymers. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/72985.

Council of Science Editors:

Yang S. Crystallization, Melting Behavior, Physical Properties, and Physical Aging of Ethylene/1-Octene Copolymers. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/72985

Virginia Tech

2. Liu, Yang. Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles.

Degree: MS, Chemistry, 2010, Virginia Tech

URL: http://hdl.handle.net/10919/76922

► Polyhedral oligomeric silsesquioxanes (POSS) have attracted substantial academic interest for many years as hybrid materials and nanofillers for controlling thermal and mechanical properties, and for… (more)

▼ Polyhedral oligomeric silsesquioxanes (POSS) have attracted substantial academic interest for many years as hybrid materials and nanofillers for controlling thermal and mechanical properties, and for providing thermal and chemical resistance while retaining ease of processing. A natural extension of these studies has been working on POSS-based amphiphiles and thin film coatings. Studies at the air/water (A/W) interface have shown that trisilanol-POSS derivatives are amphiphilic and form uniform Langmuir films, whereas closed-cage POSS derivatives are hydrophobic and aggregate. In this study, two novel POSS derivatives were synthesized from PSS-(3-hydroxypropyl)-heptaisobutyl substituted (POSS-OH) and completely characterized. Weisocyanate reacted with POSS-OH, and a POSS-based triester (POSS-triester) was obtained. Trifluoroacidolysis of the POSS-triester at room temperature afforded the corresponding triacid (POSS-triacid). Purified POSS-OH, POSS-triester, and POSS-triacid were studied by using surface pressure - area per molecule (? -A) isotherms as well as Brewster angle microscopy (BAM) at the air/water (A/W) interface. Compared with previous work on trisilanol-POSS derivatives, the results indicated that POSS-triester was surface active and formed a liquid-expanded (LE) monolayer. In contrast, POSS-triacid monolayers were more condensed (LC) and were not dramatically affected by changes in pH. Results for the lift-off areas (Alift-off), limiting areas (A0), collapse areas (Ac), and collapse pressures (? c) of POSS-OH, POSS-triester, and POSS-triacid were compared to trisilanolisobutyl-POSS (TiBP) and were interpreted in terms of possible molecular conformations. Whereas, TiBP has been hypothesized to exist in a vertex-on conformation, POSS-OH and POSS-triacid packing at the A/W interface was consistent with face-on conformations. For POSS-triester, the isotherm was consistent with a vertex-on conformation at low ? , but a face-on conformation at high ? . Advisors/Committee Members: Esker, Alan R. (committeechair), Gandour, Richard D. (committee member), Morris, John R. (committee member).

Subjects/Keywords: POSS; air/water (A/W) interface; Brewster angle microscopy (BAM); ?-A isotherms; Langmuir films

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APA (6^th Edition):

Liu, Y. (2010). Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/76922

Chicago Manual of Style (16^th Edition):

Liu, Yang. “Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles.” 2010. Masters Thesis, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/76922.

MLA Handbook (7^th Edition):

Liu, Yang. “Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles.” 2010. Web. 22 Oct 2019.

Vancouver:

Liu Y. Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/76922.

Council of Science Editors:

Liu Y. Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/76922

Virginia Tech

3. Ni, Ying. Arabinoglucuronoxylan and Arabinoxylan Adsorption onto Regenerated Cellulose Films.

Degree: MS, Chemistry, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/78163

► Cellulose and hemicelluloses have attracted increasing interest as renewable biopolymers because of their abundance. Furthermore, the recognition of biomass as a sustainable and renewable source… (more)

Subjects/Keywords: Arabinoglucuronoxylan; Regenerated cellulose thin films; Arabinoxylan; Adsorption; SPR; QCM-D

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APA (6^th Edition):

Ni, Y. (2013). Arabinoglucuronoxylan and Arabinoxylan Adsorption onto Regenerated Cellulose Films. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78163

Chicago Manual of Style (16^th Edition):

Ni, Ying. “Arabinoglucuronoxylan and Arabinoxylan Adsorption onto Regenerated Cellulose Films.” 2013. Masters Thesis, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/78163.

MLA Handbook (7^th Edition):

Ni, Ying. “Arabinoglucuronoxylan and Arabinoxylan Adsorption onto Regenerated Cellulose Films.” 2013. Web. 22 Oct 2019.

Vancouver:

Ni Y. Arabinoglucuronoxylan and Arabinoxylan Adsorption onto Regenerated Cellulose Films. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/78163.

Council of Science Editors:

Ni Y. Arabinoglucuronoxylan and Arabinoxylan Adsorption onto Regenerated Cellulose Films. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/78163

Virginia Tech

4. Tan, Xinyi. Adsorption of Blood Proteins onto Polysaccharide Surfaces.

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

URL: http://hdl.handle.net/10919/78309

► In this study, surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation monitoring (QCM-D) were combined to investigate the adsorption behavior of two platelet… (more)

Subjects/Keywords: albumin; fibrinogen; cellulose acetate; cellulose; thin films; adsorption

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APA (6^th Edition):

Tan, X. (2016). Adsorption of Blood Proteins onto Polysaccharide Surfaces. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78309

Chicago Manual of Style (16^th Edition):

Tan, Xinyi. “Adsorption of Blood Proteins onto Polysaccharide Surfaces.” 2016. Masters Thesis, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/78309.

MLA Handbook (7^th Edition):

Tan, Xinyi. “Adsorption of Blood Proteins onto Polysaccharide Surfaces.” 2016. Web. 22 Oct 2019.

Vancouver:

Tan X. Adsorption of Blood Proteins onto Polysaccharide Surfaces. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/78309.

Council of Science Editors:

Tan X. Adsorption of Blood Proteins onto Polysaccharide Surfaces. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/78309

Virginia Tech

5. Wagner, Alec Thomas. Fundamental Studies of Two Important Atmospheric Oxidants, Ozone and Hydroxyl Radical, Reacting with Model Organic Surfaces.

Degree: MS, Chemistry, 2012, Virginia Tech

URL: http://hdl.handle.net/10919/45093

► Heterogeneous reactions between gas-phase oxidants and particulate-phase organic compounds impact many important atmospheric chemical processes. For example, little is known about the reaction dynamics of… (more)

Subjects/Keywords: Rotational State Selection; Electrostatic Hexapole; Ozone; Hydroxyl Radical; Pentacene; Linear Stark Effect

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APA (6^th Edition):

Wagner, A. T. (2012). Fundamental Studies of Two Important Atmospheric Oxidants, Ozone and Hydroxyl Radical, Reacting with Model Organic Surfaces. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/45093

Chicago Manual of Style (16^th Edition):

Wagner, Alec Thomas. “Fundamental Studies of Two Important Atmospheric Oxidants, Ozone and Hydroxyl Radical, Reacting with Model Organic Surfaces.” 2012. Masters Thesis, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/45093.

MLA Handbook (7^th Edition):

Wagner, Alec Thomas. “Fundamental Studies of Two Important Atmospheric Oxidants, Ozone and Hydroxyl Radical, Reacting with Model Organic Surfaces.” 2012. Web. 22 Oct 2019.

Vancouver:

Wagner AT. Fundamental Studies of Two Important Atmospheric Oxidants, Ozone and Hydroxyl Radical, Reacting with Model Organic Surfaces. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/45093.

Council of Science Editors:

Wagner AT. Fundamental Studies of Two Important Atmospheric Oxidants, Ozone and Hydroxyl Radical, Reacting with Model Organic Surfaces. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/45093

Virginia Tech

6. Qian, Chen. Adsorption of Xyloglucan onto Cellulose and Cellulase onto Self-assembled Monolayers.

Degree: MS, Chemistry, 2012, Virginia Tech

URL: http://hdl.handle.net/10919/42496

► Adsorption of xyloglucan (XG) onto thin desulfated nanocrystalline cellulose (DNC) films was studied by surface plasmon resonance spectroscopy (SPR), quartz crystal microbalance with dissipation monitoring… (more)

Subjects/Keywords: cellulase; self-assembled monolayers; xyloglucan; cellulose thin films; adsorption

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APA (6^th Edition):

Qian, C. (2012). Adsorption of Xyloglucan onto Cellulose and Cellulase onto Self-assembled Monolayers. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42496

Chicago Manual of Style (16^th Edition):

Qian, Chen. “Adsorption of Xyloglucan onto Cellulose and Cellulase onto Self-assembled Monolayers.” 2012. Masters Thesis, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/42496.

MLA Handbook (7^th Edition):

Qian, Chen. “Adsorption of Xyloglucan onto Cellulose and Cellulase onto Self-assembled Monolayers.” 2012. Web. 22 Oct 2019.

Vancouver:

Qian C. Adsorption of Xyloglucan onto Cellulose and Cellulase onto Self-assembled Monolayers. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/42496.

Council of Science Editors:

Qian C. Adsorption of Xyloglucan onto Cellulose and Cellulase onto Self-assembled Monolayers. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/42496

7. Wang, Guanyu. The Dynamics of Gas-Surface Energy Transfer in Collisions of Diatomic Gases with Organic Surfaces.

Degree: MS, Chemistry, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/51179

► Understanding interfacial interactions at the molecular level is important for interpreting and predicting the dynamics and mechanisms of all chemistry processes. A thorough understanding of… (more)

▼ Understanding interfacial interactions at the molecular level is important for interpreting and predicting the dynamics and mechanisms of all chemistry processes. A thorough understanding of the interaction dynamics and energy transfer between gas molecules and surfaces is essential for the study of various chemical reactions. The collisions of diatomic molecules on organic surfaces are crucial to the study of atmospheric chemistry. Molecular beam scattering experiments performed in ultra-high vacuum chambers provide insight into the dynamics of gas-surface interactions. Many questions remain to be answered in the study of gas-surface interfacial chemistry. For example, what affects the energy transfer between gas molecules and surfaces? How do intermolecular forces affect the interfacial interaction dynamics? We have approached these questions by scattering diatomic gas molecules from functionalized self-assembled monolayers (SAMs). Our results indicate that the intermolecular forces between gas molecules and surfaces play an important role in the energy transfer processes. Moreover, the stronger the intermolecular forces, the more often the incident molecules come into thermal equilibrium with the surface. Furthermore, most of the previous approaches toward understanding gas-surface interaction dynamics considered the interactions as independent incidents. By scattering O2, N2, CO and NO on both CH3- and OH- terminated SAM, we found a correlation between the gas-surface interactions and a bulk property, solubility. Both being strongly affected by intermolecular forces, the gas-surface energy transfer and solubility of gases in surface-similar solvents (water for OH-SAM, n-hexane for CH3-SAM) have a positive correlation. This correlation facilitates the understanding of interfacial dynamics at the molecular level, and helps predict the outcome of the similar-size gas collisions on surfaces. Advisors/Committee Members: Morris, John R. (committeechair), Esker, Alan R. (committee member), Tissue, Brian M. (committee member).

Subjects/Keywords: Self-assembled monolayers; Molecular beam; Ultra-high vacuum; Energy transfer; Solubility

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APA (6^th Edition):

Wang, G. (2015). The Dynamics of Gas-Surface Energy Transfer in Collisions of Diatomic Gases with Organic Surfaces. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/51179

Chicago Manual of Style (16^th Edition):

Wang, Guanyu. “The Dynamics of Gas-Surface Energy Transfer in Collisions of Diatomic Gases with Organic Surfaces.” 2015. Masters Thesis, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/51179.

MLA Handbook (7^th Edition):

Wang, Guanyu. “The Dynamics of Gas-Surface Energy Transfer in Collisions of Diatomic Gases with Organic Surfaces.” 2015. Web. 22 Oct 2019.

Vancouver:

Wang G. The Dynamics of Gas-Surface Energy Transfer in Collisions of Diatomic Gases with Organic Surfaces. [Internet] [Masters thesis]. Virginia Tech; 2015. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/51179.

Council of Science Editors:

Wang G. The Dynamics of Gas-Surface Energy Transfer in Collisions of Diatomic Gases with Organic Surfaces. [Masters Thesis]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/51179

Virginia Tech

8. Du, Xiaosong. Adsorption Studies of Polysaccharides and Phospholipids Onto Cellulose.

Degree: PhD, Chemistry, 2011, Virginia Tech

URL: http://hdl.handle.net/10919/30161

► Interactions between biomolecules and cellulose films at solid/liquid interfaces was studied by surface plasmon resonance spectroscopy (SPR), quartz crystal microbalance with dissipation monitoring (QCM-D) and… (more)

▼ Interactions between biomolecules and cellulose films at solid/liquid interfaces was studied by surface plasmon resonance spectroscopy (SPR), quartz crystal microbalance with dissipation monitoring (QCM-D) and in situ atomic force microscopy (AFM) measurements. This dissertation shows the porous character of nanocrystalline cellulose films as the key feature for enhanced adsorption of chemically modified polysaccharides and provides quantitative analysis of polymer supported phospholipid structures as a stable platform for studying membrane-related processes. Smooth cellulose I films were prepared by spincoating cellulose nanocrystal suspensions onto positively charged self-assembled monolayers on gold. The adsorption of pullulan cinnamate (PC) onto cellulose surfaces increased with increasing degree of cinnamate substitution. The interactions between PCs with higher degree of substitution (DS) and porous nanocrystalline cellulose (NC) films presumably generated looped multilayer PC structures that adsorbed more than twice as much onto NC films than onto regenerated cellulose (RC) films. PC chains not only covered the NC surface but also penetrated into the porous film. The porous features of NC film are responsible for the greater adsorption of polymer chains relative to tightly packed RC films. Adsorption of phospholipid vesicles onto RC and NC films was also studied. Aggregates of intact vesicle were observed on NC surfaces with high water content ~ 84 % by mass. Phospholipid patches with smooth features were found to assemble onto RC surfaces with a lower degree of hydration ~ 30 % by mass. Vesicle membrane breakage was triggered by a destabilizing agent, LysoPC. The great mass decrease, and changes in dissipation and degree of hydration for phospholipid structures after exposure to LysoPC corresponded to the transformation from vesicles to layered structures. Initial binding of LysoPC micelles to unruptured vesicles was clearly resolved in SPR, whereas the huge mass decrease associated with bound water hides the initial adsorption of LysoPC onto vesicles in QCM-D experiments. The intitial binding of LysoPC micelles onto vesicle membranes lasted for 200 seconds with a maximal increase of 14 % by mass prior to vesicle collapse. The role of cholesterol in phospholipid interactions with model cellulose surfaces was also considered. Supported vesicle layers over RC surfaces were observed for vesicle membranes containing â ¥ 6.3 % by mole cholesterol, whereas phospholipid or phospholipid with lower cholesterol content formed disconnected lipid islands on RC surfaces. Meanwhile, intact vesicles were always observed on NC surfaces for phospholipid/cholesterol blends regardless of the cholesterol content. The intact vesicles on cellulose surfaces were attributed to the ability of cholesterol to accommodate vesicle deformation. These studies showed the impact of mesoscale structure of cellulose films on adsorbates. It sheds light on the role of the lignin-carbonhydrate-complex in plant cell wall structure and will… Advisors/Committee Members: Esker, Alan R. (committeechair), Marand, Hervé L. (committee member), Morris, John R. (committee member), Madsen, Louis A. (committee member).

Subjects/Keywords: Phospholipid Vesicles; Cellulose Film; Atomic Force Microscopy; Surface Plasmon Resonance Spectroscopy; Quartz Crystal Microbalance with Dissipation Moni; Polysaccharide

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APA (6^th Edition):

Du, X. (2011). Adsorption Studies of Polysaccharides and Phospholipids Onto Cellulose. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30161

Chicago Manual of Style (16^th Edition):

Du, Xiaosong. “Adsorption Studies of Polysaccharides and Phospholipids Onto Cellulose.” 2011. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/30161.

MLA Handbook (7^th Edition):

Du, Xiaosong. “Adsorption Studies of Polysaccharides and Phospholipids Onto Cellulose.” 2011. Web. 22 Oct 2019.

Vancouver:

Du X. Adsorption Studies of Polysaccharides and Phospholipids Onto Cellulose. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/30161.

Council of Science Editors:

Du X. Adsorption Studies of Polysaccharides and Phospholipids Onto Cellulose. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/30161

Virginia Tech

9. Wan, Guigui. Mechanisms of biogenic formaldehyde generation in wood.

Degree: PhD, Learning Sciences and Technologies, 2017, Virginia Tech

URL: http://hdl.handle.net/10919/84503

► This work addresses biogenic formaldehyde (CH₂O) generated by wood during the manufacture of non-structural wood-based composites, from which CH₂O emissions are regulated. The target for… (more)

▼ This work addresses biogenic formaldehyde (CH₂O) generated by wood during the manufacture of non-structural wood-based composites, from which CH₂O emissions are regulated. The target for regulation has been anthropogenic CH₂O released from hydrolytically unstable amino resins like urea-formaldehyde. However, current regulations (the Formaldehyde Standards for Composite Wood Products Act, signed into law in 2010 and implemented in 2016) restrict allowable emissions to such low levels that biogenic CH₂O may affect regulation compliance. The industry has met the latest regulations with new amino resin technologies. Nevertheless persistent anecdotal reports suggest that biogenic CH₂O complicates regulation compliance. This work represents an industry/university cooperation to seek a more thorough understanding of biogenic CH₂O, to begin documentation of biogenic CH₂O levels in wood, and to study the conditions and chemical mechanisms of its formation. Efforts began by establishing CH₂O analysis using the fluorimetric acetylacetone determination. A custom 12-liter chamber with controlled temperature and relative humidity, and "ultrapure" nitrogen (N₂) ventilation was created to measure CH₂O emissions from flakes sampled from four Virginia pine (Pinus virginiana) trees. Emissions from never-heated specimens varied significantly among the four trees, ranging from 0.02 – 0.19 µg CH₂O/m³g dry wood. Heating (200°C, 1 hour), followed by chamber equilibration, resulted in significantly increased emissions on the order of 50%. Sequential heating, followed by chamber equilibration (in other words, heat/equilibrate/measure emission/repeat), resulted in declining emissions suggesting that a finite chemical source of CH₂O was being depleted by the sequential heat treatment. Flake specimens were stored in the open laboratory, and over 2-3 months laboratory storage, initially high emitting specimens gradually emitted less CH₂O, and initially low emitters gradually emitted more CH₂O. Concerns over laboratory contamination were perhaps allayed when background levels of laboratory CH₂O were determined to be similar to the background levels in the ultrapure N₂ used to ventilate the chamber. Measurement of emissions was abandoned, and thereafter a simple water extraction technique (~ 94% CH₂O recovery) was used to measure the CH₂O content of never-heated and heated wood specimens, where the difference was identified as CH₂O generated due to heating. Increment cores from living Virginia pine (Pinus virginiana), yellow-poplar (Liriodendron tulipifera), and radiata pine (Pinus radiata) trees were used to measure CH₂O content and CH₂O generation due to heating (200°C, 10 min). Significant variations within and between trees of the same species were observed. Tissue types (juvenile/mature, heartwood/sapwood) sometimes correlated to higher CH₂O contents and greater heat-generation potential; but sometimes not depending upon species. Heating increased CH₂O levels 3-60 fold. Heating with high moisture levels caused greater CH₂O generation than… Advisors/Committee Members: Frazier, Charles E. (committeechair), Renneckar, Scott Harold (committee member), Esker, Alan R. (committee member), Roman, Maren (committee member), Goodell, Barry (committee member).

Subjects/Keywords: wood; biogenic formaldehyde; polymer; lignin; extractives

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APA (6^th Edition):

Wan, G. (2017). Mechanisms of biogenic formaldehyde generation in wood. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/84503

Chicago Manual of Style (16^th Edition):

Wan, Guigui. “Mechanisms of biogenic formaldehyde generation in wood.” 2017. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/84503.

MLA Handbook (7^th Edition):

Wan, Guigui. “Mechanisms of biogenic formaldehyde generation in wood.” 2017. Web. 22 Oct 2019.

Vancouver:

Wan G. Mechanisms of biogenic formaldehyde generation in wood. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/84503.

Council of Science Editors:

Wan G. Mechanisms of biogenic formaldehyde generation in wood. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/84503

Virginia Tech

10. Mohammadi, Hadi. On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene.

Degree: PhD, Chemistry, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/84921

► The crystallization and melting behaviors of an ethylene/1-hexene copolymer and series of narrow molecular weight linear polyethylene and poly(ethylene oxide) fractions were studied using a… (more)

▼ The crystallization and melting behaviors of an ethylene/1-hexene copolymer and series of narrow molecular weight linear polyethylene and poly(ethylene oxide) fractions were studied using a combination of ultra-fast and conventional differential scanning calorimetry, optical microscopy, small angle X-ray scattering, and wide angle X-ray diffraction. In the case of linear polyethylene and poly(ethylene oxide), the zero-entropy production melting temperatures of initial lamellae of isothermally crystallized fractions were analyzed in the context of the non-linear Hoffman-Weeks method. Using the Huggins equation, limiting equilibrium melting temperatures of 141.4 ± 0.8 °C and 81.4 ± 1.0 °C were estimated for linear polyethylene and poly(ethylene oxide), respectively. The former and the latter are about 4 °C lower and 12.5 °C higher than these predicted by Flory/Vrij and Buckley/Kovacs, respectively. Accuracy of the non-linear Hoffman-Weeks method was also examined using initial lamellar thickness literature data for a linear polyethylene fraction at different crystallization temperatures. The equilibrium melting temperature obtained by the Gibbs-Thomson approach and the C2 value extracted from the initial lamellar thickness vs. reciprocal of undercooling plot were similar within the limits of experimental error to those obtained here through the non-linear Hoffman-Weeks method. In the next step, the Lauritzen-Hoffman (LH) secondary nucleation theory was modified to account for the effect of stem length fluctuations, tilt angle of the crystallized stems, and temperature dependence of the lateral surface free energy. Analysis of spherulite growth rate and wide angle X-ray diffraction data for 26 linear polyethylene and 5 poly(ethylene oxide) fractions revealed that the undercooling at the regime I/II transition, the equilibrium fold surface free energy, the strength of the stem length fluctuations and the substrate length at the regime I/II transition are independent of chain length. The value of the equilibrium fold surface free energy derived from crystal growth rate data using the modified Lauritzen-Hoffman theory matches that calculated from lamellar thickness and melting data through the Gibbs-Thomson equation for both linear polyethylene and poly(ethylene oxide). Larger spherulitic growth rates for linear polyethylene than for poly(ethylene oxide) at low undercooling is explained by the higher secondary nucleation constant of poly(ethylene oxide). While the apparent friction coefficient of a crystallizing linear polyethylene chain is 2 to 8 times higher than that of a chain undergoing reptation in the melt state, the apparent friction coefficient of a crystallizing poly(ethylene oxide) chain is about two orders of magnitude lower. This observation suggests that segmental mobility on the crystal phase plays a significant role in the crystal growth process. In case of the statistical ethylene/1-hexene copolymer, the fold surface free energies of the copolymer lamellae at the time of crystallization and melting increase… Advisors/Committee Members: Marand, Hervé L. (committeechair), Moore, Robert Bowen (committee member), Esker, Alan R. (committee member), Baird, Donald G. (committee member).

Subjects/Keywords: Melting and Crystallization of Polymers; Polyethylene; Poly(ethylene oxide); Metallocene Linear Low-Density Polyethylene; Lauritzen-Hoffman Secondary Nucleation Theory; Spherulite Growth Rate; Lamellar Thickness; Friction Coefficient

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APA (6^th Edition):

Mohammadi, H. (2018). On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/84921

Chicago Manual of Style (16^th Edition):

Mohammadi, Hadi. “On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene.” 2018. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/84921.

MLA Handbook (7^th Edition):

Mohammadi, Hadi. “On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene.” 2018. Web. 22 Oct 2019.

Vancouver:

Mohammadi H. On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/84921.

Council of Science Editors:

Mohammadi H. On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/84921

Virginia Tech

11. Wang, Chao. Renewable Natural Polymer Thin Films and Their Interactions with Biomacromolecules.

Degree: PhD, Chemistry, 2014, Virginia Tech

URL: http://hdl.handle.net/10919/64909

► Natural polymers from renewable resources have attracted increasing interest as candidates for renewable energy and functional materials. In this work, the interactions between natural polymer… (more)

▼ Natural polymers from renewable resources have attracted increasing interest as candidates for renewable energy and functional materials. In this work, the interactions between natural polymer thin films and biomacromolecules were studied via surface analysis techniques, such as a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM). Chitinase activity on regenerated chitin (RChitin) films was studied by QCM-D and AFM. The optimal temperature and pH for chitinase activity on surfaces determined by QCM-D and AFM were consistent with bulk solution studies in the literature. Results from QCM-D also indicated that chitinase showed higher activity on fully acetylated chitin than highly deacetylated chitosan. Nanocrystalline chitin (Chitin NC) thin films were prepared by spincoating a nanocrystalline chitin colloidal suspension onto solid surfaces. Solvent exchange experiments via QCM-D with H2O/D2O revealed that Chitin NC films had more water than RChitin films of similar thickness. Results from QCM-D demonstrated that Chitin NC films had high bovine serum albumin loading capacity, and chitinase not only degraded, but also caused swelling of the chitin nanocrystals. Adsorption of human serum albumin (HSA) and fibrinogen (HFN) onto bare gold, regenerated cellulose (RC) and RChitin thin films was studied by SPR and QCM-D. Studies by SPR indicated that HSA and HFN formed close-packed monolayers on gold surfaces and sub-monolayers on polysaccharide surfaces, and the adsorption affinity of HSA for polysaccharide surfaces was greater than that of HFN. Results from QCM-D and SPR showed that the protein layers on polysaccharide surfaces had more associated water than proteins on gold surfaces. The dehydrogenative polymerization of monolignols catalyzed by physically immobilized horseradish peroxidase was investigated using QCM-D and AFM. Results from QCM-D and AFM showed that coniferyl and p-coumaryl alcohol underwent polymerization directly, whereas sinapyl alcohol required the addition of a nucleophile for polymerization. Studies by QCM-D and AFM also indicated that the surface-initiated polymerization was greatly affected by the support surface, monolignol concentration, hydrogen peroxide concentration and temperature. Thin films of dehydrogenative polymer (DHP), kraft (KL), organosolv (OL) and milled wood (MWL) lignins were used to study the enzymatic degradation of lignin mediated by lignin peroxidase (LiP) and manganese peroxidase (MnP). Results from QCM-D showed that the initial rates for degradation catalyzed by LiP increased in the order: KL < OL < MWL < guaiacyl DHP (G-DHP) < p-hydroxyphenyl DHP (H-DHP). In contrast, manganese peroxidase only degraded DHP films with a faster initial rate for G-DHP than H-DHP. Adsorption of hemicelluloses onto KL, OL and MWL thin films was studied by QCM-D and SPR. Results from QCM-D showed that hemicelluloses with different structures displayed very different adsorption… Advisors/Committee Members: Esker, Alan R. (committeechair), Gibson, Harry W. (committee member), Edgar, Kevin J. (committee member), Turner, Sam Richard (committee member).

Subjects/Keywords: Chitin; Lignin; Cellulose; Hemicelluloses; Proteins; Thin Films; Enzymatic Degradation; Adsorption; Quartz Crystal Microbalance with Dissipation Monitoring; Surface Plasmon Resonance; Atomic Force Microscopy

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APA (6^th Edition):

Wang, C. (2014). Renewable Natural Polymer Thin Films and Their Interactions with Biomacromolecules. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/64909

Chicago Manual of Style (16^th Edition):

Wang, Chao. “Renewable Natural Polymer Thin Films and Their Interactions with Biomacromolecules.” 2014. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/64909.

MLA Handbook (7^th Edition):

Wang, Chao. “Renewable Natural Polymer Thin Films and Their Interactions with Biomacromolecules.” 2014. Web. 22 Oct 2019.

Vancouver:

Wang C. Renewable Natural Polymer Thin Films and Their Interactions with Biomacromolecules. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/64909.

Council of Science Editors:

Wang C. Renewable Natural Polymer Thin Films and Their Interactions with Biomacromolecules. [Doctoral Dissertation]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/64909

Virginia Tech

12. 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 October 22, 2019. 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. 22 Oct 2019.

Vancouver:

Savage A. Synthesis and Solution Properties of Semi-rigid Polyelectrolytes and Polyampholytes. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2019 Oct 22]. 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

13. Pillai, Karthik. Bio-inspired Cellulose Nanocomposites.

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

URL: http://hdl.handle.net/10919/28575

► Natural composites like wood are scale-integrated structures that range from molecular to the macroscopic scale. Inspired by this design, layer-by-layer (LbL) deposition technique was used… (more)

▼ Natural composites like wood are scale-integrated structures that range from molecular to the macroscopic scale. Inspired by this design, layer-by-layer (LbL) deposition technique was used to create lignocellulosic composites from isolated wood polymers namely cellulose and lignin, with a lamellar architecture. In the first phase of the study, adsorption of alkali lignin onto cationic surfaces was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Complete coverage of the cationic surface with alkali lignin occured at low solution concentration; large affinity coefficients were calculated for this system at differing pH levels. Adsorption studies with organosolv lignin in an organic solvent, and spectroscopic analysis of mixtures of cationic polymer with alkali lignin revealed a non-covalent interaction. The work demonstrated how noncovalent interactions could be exploited to molecular organize thin polyphenolic biopolymers on cationic surfaces. The second phase of the study examined the adsorption steps during the LbL assembly process to create novel lignocellulosic composites. LbL assembly was carried out using oxidized nanocellulose (NC) and lignin, along with a cationic polymer poly(diallyldimethylammonium chloride) (PDDA). QCM-D was used to follow the sequential adsorption process of the three different polymers. Two viscoelastic models, namely Johannsmann and Voigt, were respectively used to calculate the areal mass and thickness of the adsorbed layers. Atomic force microscopy studies showed a complete coverage of the surface with lignin in all the disposition cycles, however, surface coverage with NC was seen to increase with the number of layers. Free-standing composite films were obtained when the LbL process was carried out for 250 deposition cycles (500 bilayers) on a cellulose acetate substrate, following the dissolution of the substrate in acetone. Scanning electron microscopy of the cryo-fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle was estimated to be 17 nm. The third phase of the study investigated the effect of LbL ordering of the polymers versus a cast film composed of a blended mixture of the polymers, using dynamic mechanical analysis. A tan ï ¤ peak was observed in the 30 â 40 ÂºC region for both films, which was observed in the neat NC film. Heating of the samples under a compressive force produced opposite effects in the films, as the LbL films exhibited swelling, whereas the cast films showed densification. The apparent activation energy of this transition (65 â 80 kJ mol-1) in cast films, calculated based on the Arrhenius equation was found to be coincident to those reported for the ï ¢ transition of amorphous cellulose. The peak was seen to disappear in case of LbL films in the second heat, whereas it was recurring in case of cast films of the blended mixture, and neat NC films. Altogether, the together the work details a novel path to integrate an organized lignin and cellulose molecular structure,… Advisors/Committee Members: Renneckar, Scott Harold (committeechair), Roman, Maren (committee member), Esker, Alan R. (committee member), Frazier, Charles E. (committee member), Edgar, Kevin J. (committee member).

Subjects/Keywords: Nanocellulose; Nanocomposite; Biomimetic; Layer-by-layer (LbL); QCM-D; AFM

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APA (6^th Edition):

Pillai, K. (2011). Bio-inspired Cellulose Nanocomposites. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28575

Chicago Manual of Style (16^th Edition):

Pillai, Karthik. “Bio-inspired Cellulose Nanocomposites.” 2011. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/28575.

MLA Handbook (7^th Edition):

Pillai, Karthik. “Bio-inspired Cellulose Nanocomposites.” 2011. Web. 22 Oct 2019.

Vancouver:

Pillai K. Bio-inspired Cellulose Nanocomposites. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/28575.

Council of Science Editors:

Pillai K. Bio-inspired Cellulose Nanocomposites. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/28575

Virginia Tech

14. Liu, Yang. Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles.

Degree: PhD, Chemistry, 2011, Virginia Tech

URL: http://hdl.handle.net/10919/77182

► Polyhedral oligomeric silsesquioxanes (POSS) have attracted substantial academic interest for many years as hybrid materials and nanofillers for controlling thermal and mechanical properties, and providing… (more)

▼ Polyhedral oligomeric silsesquioxanes (POSS) have attracted substantial academic interest for many years as hybrid materials and nanofillers for controlling thermal and mechanical properties, and providing thermal and chemical resistance while retaining ease of processing. A natural extension of these studies has been POSS-based amphiphiles and thin film coatings. Studies at the air/water (A/W) interface have shown that trisilanol-POSS derivatives are amphiphilic and form uniform Langmuir films, whereas closed-cage POSS derivatives are hydrophobic and aggregate. In previous work, a triester (POSS-triester) and a triacid (POSS-triacid) were synthesized from PSS-(3-hydroxypropyl)-heptaisobutyl (POSS-OH) and Weisocyanate and fully characterized by surface pressure – area per molecule (Π-A) isotherm and Brewster angle microscopy (BAM) studies at the A/W interface. The results indicated that POSS-triester is surface active forming a liquid expanded (LE) monolayer, whereas POSS-triacid forms a liquid condensed (LC) monolayer that is only weakly affected by pH. A face-on conformation was proposed and examined to understand the packing of POSS-based amphiphilic molecules at the A/W interface. The face-on/vertex-on comparison is rarely discussed for Langmuir monolayers at the A/W interface. In this thesis, three other POSS-based esters were synthesized from POSS-OH and aminopropylisobutyl-POSS (POSS-NH₂) using Weisocyanate and a similar isocyanate containing two tert-butyl protected carboxylic acids. The synthesized materials are characterized by Π-A isotherm and BAM. For POSS-OH based diester (PAlDE) and POSS-NH2 based diester (PAmDE), LE/LC phase transitions were observed in Π-A isotherms over part of the experimentally accessible temperature range and were attributed to a change from a vertex-on to face-on conformation. Apparent BAM images confirmed LC islands coexisted with the LE phase. The experimentally observed dynamic estimates of the critical temperatures (Tc) were estimated from a two-dimensional Clausius-Clapeyron analysis and were consistent with the temperature dependence of the Π-A isotherms. These LE/LC phase transitions are the first observed for POSS amphiphiles. Advisors/Committee Members: Esker, Alan R. (committeechair), Marand, Hervé L. (committee member), Gandour, Richard D. (committee member), Morris, John R. (committee member).

Subjects/Keywords: Π–A isotherms; air/water (A/W) interface; Brewster angle microscopy (BAM); POSS; Langmuir films

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

APA (6^th Edition):

Liu, Y. (2011). Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77182

Chicago Manual of Style (16^th Edition):

Liu, Yang. “Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles.” 2011. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/77182.

MLA Handbook (7^th Edition):

Liu, Yang. “Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles.” 2011. Web. 22 Oct 2019.

Vancouver:

Liu Y. Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/77182.

Council of Science Editors:

Liu Y. Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/77182

Virginia Tech

15. Jiang, Feng. Effects of the Non-ionic Surfactant Tween 80 on the Enzymatic Hydrolysis of Model Cellulose and Lignocellulosic Substrates.

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

URL: http://hdl.handle.net/10919/77223

► Non-ionic surfactants are known to enhance the biochemical conversion of lignocellulosic (LC) biomass to bioethanol. Their mechanisms of action, however, are incompletely understood. This research… (more)

▼ Non-ionic surfactants are known to enhance the biochemical conversion of lignocellulosic (LC) biomass to bioethanol. Their mechanisms of action, however, are incompletely understood. This research was conducted to elucidate the effects of the non-ionic surfactant Tween 80 on the enzymatic hydrolysis of cellulose and LC substrates. Model cellulose substrates were prepared from cellulose nanocrystals (CNCs) obtained by sulfuric acid hydrolysis of wood pulp. Two methods were developed for the removal of the sulfate groups on the CNCs, resulting from the use of sulfuric acid in their preparation. The effect of sulfate groups, which may be introduced into LC biomass during pretreatment with sulfuric acid, on the enzymatic hydrolysis of cellulose was studied with model cellulose substrates prepared from CNCs with different sulfate group densities. Adsorption of cellulases onto sulfated substrates increased with increasing sulfate group density but their rate of hydrolysis decreased. The decrease indicated an inhibitory effect of sulfate groups on the enzymatic hydrolysis of cellulose, possibly due to non-productive binding of the cellulases onto the substrates through electrostatic interactions instead of their cellulose binding domains. The effect of Tween 80 on the adsorption of cellulases onto lignin, often present as residual lignin in pretreated biomass, was studied with model lignin substrates, prepared from kraft lignin, organosolv lignin, and milled wood lignin. Cellulases appeared to adsorb onto the lignin substrates via both hydrophobic and polar interactions. Tween 80 molecules on the lignin substrates seemed to hinder cellulase adsorption via hydrophobic interactions and reduced the adsorption rate. Finally, the effects of lignin and Tween 80 on the enzymatic hydrolysis of cellulose and LC substrates were studied. Lignin hindered both the adsorption of cellulases onto the substrates and the enzymatic hydrolysis of the substrates. Tween 80 was found to form surfactant–protein complexes with cellulases in solution without compromising cellulase activity. Either substrate-adsorbed or in solution, Tween 80 had no effect on the hydrolysis of cellulose by cellulases. Substrate-adsorbed Tween 80 increased the apparent enzymatic hydrolysis rates of LC substrates but the ability of Tween 80 to increase their apparent hydrolysis rate depended strongly on their structural properties and the chemical properties of the lignin. Hence, Tween 80 may be able to mitigate the inhibitory effect of lignin on the enzymatic hydrolysis of pretreated biomass. Advisors/Committee Members: Roman, Maren (committeechair), Frazier, Charles E. (committee member), Edgar, Kevin J. (committee member), Esker, Alan R. (committee member), Renneckar, Scott H. (committee member).

Subjects/Keywords: biomass; adsorption; bioethanol; cellulases; lignin; cellulose nanocrystals

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

APA (6^th Edition):

Jiang, F. (2011). Effects of the Non-ionic Surfactant Tween 80 on the Enzymatic Hydrolysis of Model Cellulose and Lignocellulosic Substrates. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77223

Chicago Manual of Style (16^th Edition):

Jiang, Feng. “Effects of the Non-ionic Surfactant Tween 80 on the Enzymatic Hydrolysis of Model Cellulose and Lignocellulosic Substrates.” 2011. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/77223.

MLA Handbook (7^th Edition):

Jiang, Feng. “Effects of the Non-ionic Surfactant Tween 80 on the Enzymatic Hydrolysis of Model Cellulose and Lignocellulosic Substrates.” 2011. Web. 22 Oct 2019.

Vancouver:

Jiang F. Effects of the Non-ionic Surfactant Tween 80 on the Enzymatic Hydrolysis of Model Cellulose and Lignocellulosic Substrates. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/77223.

Council of Science Editors:

Jiang F. Effects of the Non-ionic Surfactant Tween 80 on the Enzymatic Hydrolysis of Model Cellulose and Lignocellulosic Substrates. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/77223

Virginia Tech

16. Kumar, Ashutosh. Towards a Reduced-Scaling Method for Calculating Coupled Cluster Response Properties.

Degree: PhD, Chemistry, 2018, Virginia Tech

URL: http://hdl.handle.net/10919/83846

► One of the central problems limiting the application of accurate {em ab initio} methods to large molecular systems is their high computational costs, i.e., their… (more)

▼ One of the central problems limiting the application of accurate {em ab initio} methods to large molecular systems is their high computational costs, i.e., their computing and storage requirements exhibit polynomial scaling with the size of the system. For example, the coupled cluster singles and doubles method with the perturbative inclusion of triples: the CCSD(T) model, which is considered to be the ``gold standard'' of quantum chemistry scales as {cal O}(N⁷) in its canonical formulation, where N is a measure of the system size. However, the steep scaling associated with these methods is unphysical since the property of dynamic electron correlation or dispersion (for insulators) is local in nature and decays as R^-6 power of distance. Different reduced-scaling techniques which attempt to exploit this inherent sparsity in the wavefunction have been used in conjunction with the coupled cluster theory to calculate ground-state properties of molecular systems with hundreds of heavy atoms in reasonable computational time. However, efforts towards extension of these methods for describing response properties like polarizabilities, optical rotations, etc., which are related to the derivative of the wavefunction with respect to external electric or/and magnetic fields, have been fairly limited and conventional reduced-scaling algorithms have been shown to yield large and often erratic deviations from the full canonical results. Accurate simulation of response properties like optical rotation is highly desirable as it can help the experimental chemists in understanding the structure-activity relationship of different chiral drug candidates. In this work, we identify the reasons behind the unsatisfactory performance of the pair natural orbital (PNO) based reduced-scaling approach for calculating linear response properties at the coupled cluster level of theory and propose novel modifications, which we refer to as PNO++, (A. Kumar and T. D. Crawford. Perturbed Pair Natural Orbitals for Coupled-Cluster Linear-Response Theory. 2018, {em manuscript in preparation}) that can provide the necessary accuracy at significantly lower computational costs. The motivation behind the PNO++ approach came from our works on the (frozen) virtual natural orbitals (FVNO), which can be seen as a precursor to the concept of PNOs (A. Kumar and T. D. Crawford. Frozen Virtual Natural Orbitals for Coupled-Cluster Linear-Response Theory. {em J. Phys. Chem. A}, 2017, 121(3), pp 708 716) and the improved FVNO++ method (A. Kumar and T. D. Crawford. Perturbed Natural Orbitals for Coupled-Cluster Linear-Response Theory. 2018, {em manuscript in preparation}). The essence of these modified schemes (FVNO++ and PNO++) lie in finding suitable field perturbed one-electron densities to construct ``perturbation aware" virtual spaces which, by construction, are much more compact for describing response properties, making them ideal for applications on large molecular systems. Advisors/Committee Members: Crawford, T. Daniel (committeechair), Esker, Alan R. (committee member), Valeyev, Eduard Faritovich (committee member), Troya, Diego (committee member).

Subjects/Keywords: Coupled Cluster; Reduced-Scaling; Response Properties

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

APA (6^th Edition):

Kumar, A. (2018). Towards a Reduced-Scaling Method for Calculating Coupled Cluster Response Properties. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/83846

Chicago Manual of Style (16^th Edition):

Kumar, Ashutosh. “Towards a Reduced-Scaling Method for Calculating Coupled Cluster Response Properties.” 2018. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/83846.

MLA Handbook (7^th Edition):

Kumar, Ashutosh. “Towards a Reduced-Scaling Method for Calculating Coupled Cluster Response Properties.” 2018. Web. 22 Oct 2019.

Vancouver:

Kumar A. Towards a Reduced-Scaling Method for Calculating Coupled Cluster Response Properties. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/83846.

Council of Science Editors:

Kumar A. Towards a Reduced-Scaling Method for Calculating Coupled Cluster Response Properties. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/83846

Virginia Tech

17. Sim, Jae Hyun. Studies of Interactions Between Rod-like Celulose Nanocrystals and Xylan and Pullulan Derivatives: A Light Scattering Study.

Degree: PhD, Chemistry, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/19215

► Interactions between polysaccharide derivatives and rod-like cellulose nanocrystals were studied by light scattering. Two replicates of cellulose nanocrystals (DOE-2-12A and DOE-2-12B) were probed with polarized… (more)

▼ Interactions between polysaccharide derivatives and rod-like cellulose nanocrystals were studied by light scattering. Two replicates of cellulose nanocrystals (DOE-2-12A and DOE-2-12B) were probed with polarized and depolarized dynamic light scattering. X-ray photoelectron spectroscopy experiments showed sulfate groups on cellulose nanocrystals. Decay rates from polarized dynamic light scattering experiments exhibited a significantly smaller angular dependence for both samples. However, DOE-2-12B showed a smaller angular dependence than DOE-2-12A. Lengths and diameters of DOE-2-12A and DOE-2-12B obtained by Broersma\'s formula were 229 " 19 and 19 " 7 nm and 240 " 18 and 22 " 6 nm, respectively. The resultant length and diameter of DOE-2-12B were comparable to those for cellulose whiskers obtained from cotton. Adsorption of pullulan 4-chlorocinnamate (P4CC03) onto cellulose nanocrystals (DOE-2-12B) was also studied by UV-Vis spectroscopy, zeta-potential measurements, and polarized and depolarized dynamic light scattering. UV-Vis spectroscopy of the P4CC03/water binary system and in situ light scattering showed UV crosslinking of pullulan 4-chlorocinnamate occurred in binary and ternary systems but led to different aggregation behavior in the two ternary systems: PreX where P4CC03 crosslinking occurred prior to the addition of cellulose nanocrystals and Rxn where cellulose nanocrystals were present during UV exposure. These studies showed P4CC03 adsorbed onto cellulose nanocrystals and UV induced crosslinking occurred at the surface of the cellulose nanocrystals. Zeta-potential measurements also showed that P4CC03 adsorbed onto cellulose nanocrystals. Finally, adsorption of 2-hydroxypropyltrimethylammonium xylans (HPMAXs) of degree of molar substitution MS = 0.34 onto rod-like cellulose nanocrystals (DOE-2-12Bs) were probed with zeta-potential measurements and polarized and depolarized dynamic light scattering. Zeta-potential changes of HPMAX/water, HPMAX/DOE-2-12B/water, and DOE-2-12B/water systems showed HPMAX adsorption onto DOE-2-12Bs. Intensity autocorrelation functions from Hv and Vv mode exhibited partial heterodyning. Decay time distributions of the binary and ternary systems showed that aggregates existed in the binary system but disappeared in the ternary system. These observations revealed that HPMAX adsorbed onto a fraction of the cellulose nanocrystals in the ternary system at low concentrations of HPMAX. Decreasing translational and rotational diffusion coefficients with increasing HPMAX concentration indicated HPMAX adsorption onto cellulose nanocrystals. A significant HPMAX concentration dependence of the ratio of rotational diffusion coefficient to translational diffusion coefficient showed strong adsorptive interactions between HPMAX and DOE-2-12B. These studies showed there were interactions between polysaccharides and cellulose nanocrystals even in very dilute solutions. Also, it was shown that probe diffusion studies with rod-like cellulose nanocrystals is a promising strategy for… Advisors/Committee Members: Esker, Alan R. (committeechair), Troya, Diego (committee member), Gibson, Harry W. (committee member), Madsen, Louis A. (committee member).

Subjects/Keywords: Light Scattering; Cellulose Nanocrystal; Pullulan; Xylan

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

APA (6^th Edition):

Sim, J. H. (2013). Studies of Interactions Between Rod-like Celulose Nanocrystals and Xylan and Pullulan Derivatives: A Light Scattering Study. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/19215

Chicago Manual of Style (16^th Edition):

Sim, Jae Hyun. “Studies of Interactions Between Rod-like Celulose Nanocrystals and Xylan and Pullulan Derivatives: A Light Scattering Study.” 2013. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/19215.

MLA Handbook (7^th Edition):

Sim, Jae Hyun. “Studies of Interactions Between Rod-like Celulose Nanocrystals and Xylan and Pullulan Derivatives: A Light Scattering Study.” 2013. Web. 22 Oct 2019.

Vancouver:

Sim JH. Studies of Interactions Between Rod-like Celulose Nanocrystals and Xylan and Pullulan Derivatives: A Light Scattering Study. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/19215.

Council of Science Editors:

Sim JH. Studies of Interactions Between Rod-like Celulose Nanocrystals and Xylan and Pullulan Derivatives: A Light Scattering Study. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/19215

Virginia Tech

18. Kittle, Joshua Daniel. Characterization of Cellulose and Chitin Thin Films and Their Interactions with Bio-based Polymers.

Degree: PhD, Chemistry, 2012, Virginia Tech

URL: http://hdl.handle.net/10919/26806

► As the two most abundant natural polymers on earth, cellulose and chitin have attracted increasing attention as a source of renewable energy and functional materials.… (more)

▼ As the two most abundant natural polymers on earth, cellulose and chitin have attracted increasing attention as a source of renewable energy and functional materials. Thin films of cellulose and chitin are useful for studying interactions of these materials with other natural and synthetic molecules via techniques such as quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR). Because of the difficulty of extracting native cellulose, regenerated cellulose (RC), sulfated nanocrystalline cellulose (SNC), and desulfated nanocrystalline cellulose (DNC) thin films are often studied in its place. In this work, QCM-D solvent exchange studies showed that water contents of RC, SNC and DNC films were proportional to the film thickness (d). Accessibility and degradation of the films was further analyzed via substrate exposure to cellulase. Cellulase adsorption onto RC films was independent of d, whereas cellulase adsorption onto SNC and DNC films increased with d. Enhanced access to guest molecules for SNC and DNC films relative to RC films revealed they are more porous. The porosity of these cellulose films aided in understanding the observed differences of xyloglucan (XG) adsorption onto their surfaces. Xyloglucan adsorption onto RC, SNC, and DNC was studied by QCM-D and SPR. The amount of adsorbed XG increased in the order RC < SNC < DNC. XG adsorption onto RC films was independent of d, whereas XG adsorption was weakly dependent upon d for SNC films and strongly dependent upon d for DNC films. However, XG adsorbed onto "monolayer" thin films of RC, SNC, and DNC in approximately the same amount. These results suggested that the morphology and surface charge of the cellulose substrate had a limited effect upon XG adsorption and that accessible surface area of the cellulose film may be the factor leading to apparent differences in XG adsorption for different surfaces. The porosity and surface charge of SNC films presented a unique opportunity to examine polyelectrolyte adsorption and subsequent dewatering of the SNC substrate. The adsorption of a series of cationically derivatized dextran (cDex) polyelectrolytes with various degrees of substitution (DS) onto SNC was studied using QCM-D and SPR. As the hydrophobic character of the cDex samples increased, the water content of the adsorbed cDex layer decreased. For cDex with the greatest hydrophobic content, nearly 50% by mass of the initial water present in the porous SNC film was removed upon cDex adsorption. This study indicated that the water content of the film could be tailored by controlling the DS and hydrophobic character of the polyelectrolyte. This work also presents the first report of smooth, homogeneous, ultrathin chitin films, opening the door to surface studies of binding interactions, adsorption kinetics, and enzymatic degradation. The chitin films were formed by spincoating trimethylsilyl chitin onto gold or silica substrates, followed by regeneration to a chitin film. The utility of these chitin films… Advisors/Committee Members: Esker, Alan R. (committeechair), Troya, Diego (committee member), Morris, John R. (committee member), Madsen, Louis A. (committee member).

Subjects/Keywords: Chitin; Cellulose; Surface Plasmon Resonance; Quartz Crystal Microbalance; Xyloglucan; Dextran

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APA (6^th Edition):

Kittle, J. D. (2012). Characterization of Cellulose and Chitin Thin Films and Their Interactions with Bio-based Polymers. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26806

Chicago Manual of Style (16^th Edition):

Kittle, Joshua Daniel. “Characterization of Cellulose and Chitin Thin Films and Their Interactions with Bio-based Polymers.” 2012. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/26806.

MLA Handbook (7^th Edition):

Kittle, Joshua Daniel. “Characterization of Cellulose and Chitin Thin Films and Their Interactions with Bio-based Polymers.” 2012. Web. 22 Oct 2019.

Vancouver:

Kittle JD. Characterization of Cellulose and Chitin Thin Films and Their Interactions with Bio-based Polymers. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/26806.

Council of Science Editors:

Kittle JD. Characterization of Cellulose and Chitin Thin Films and Their Interactions with Bio-based Polymers. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/26806

Virginia Tech

19. Zhang, Wei. Biopolymer Structure Analysis and Saccharification of Glycerol Thermal Processed Biomass.

Degree: PhD, Learning Sciences and Technologies, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/71830

► Glycerol thermal processing (GTP) is studied as a novel biomass pretreatment method in this research with the purposes to facilitate biopolymer fractionation and biomass saccharification.… (more)

▼ Glycerol thermal processing (GTP) is studied as a novel biomass pretreatment method in this research with the purposes to facilitate biopolymer fractionation and biomass saccharification. This approach is performed by treating sweet gum particles on polymer processing equipment at high temperatures and short times in the presence of anhydrous glycerol. Nine severity conditions are studied to assess the impact of time and temperature during the processing on biopolymer structure and conversion. The GTP pretreatment results in the disruption of cell wall networks by increasing the removal of side-chain sugars and lignin-carbohydrate linkages based on severity conditions. After pretreatment, 41% of the lignin and 68% of the xylan is recovered in a dry powdered form by subsequent extractions without additional catalysts, leaving a relatively pure cellulose fraction, 84% glucan, as found in chemical pulps. Lignin structural analysis indicated GTP processing resulted in extensive degradation of B-aryl ether bonds through the C-y elimination, followed by abundant phenolic hydroxyl liberation. At the same time, condensation occurred in the GTP lignin, providing relatively high molecular weight, near to that of the enzymatic mild acidolysis lignin. Better thermal stability was observed for this GTP lignin. In addition to lignin, xylan was successfully isolated as another polymer stream after GTP pretreatment. The recovered water insoluble xylan (WIX) was predominant alkali soluble fraction with a maximum purity of 84% and comparable molecular weight to xylan isolated from non-pretreated fibers. Additionally, the narrow molecular weight distribution of recovered WIX, was arisen from the pre-extraction of low molecular weight water-soluble xylan. Additionally, a 20-fold increase of the ultimate enzymatic saccharification for GTP pretreated biomass was observed even with significant amounts of lignin and xylan remaining on the non-extracted fiber. The shear and heat processing caused a disintegrated cell wall structure with formation of biomass debris and release of cellulose fibrils, enhancing surface area and most likely porosity. These structural changes were responsible for the improved biomass digestibility. Additionally, no significant inhibitory compounds for saccharification are produced during GTP processing, even at high temperatures. While lignin extraction did not promote improvement in hydrolysis rates, further xylan extraction greatly increases the initial enzymatic hydrolysis rate and final level of saccharification. The serial of studies fully demonstrate glycerol thermal processing as a novel pretreatment method to enhance biomass saccharification for biofuel production, as well as facilitate biopolymer fractionation. Moreover, the study shows the impact of thermally introduced structural changes to wood biopolymers when heated in anhydrous environments in the presence of hydrogen bonding solvent. Advisors/Committee Members: Renneckar, Scott Harold (committeechair), Goodell, Barry (committee member), Barone, Justin Robert (committee member), Frazier, Charles E. (committee member), Esker, Alan R. (committee member).

Subjects/Keywords: glycerol thermal processing; lignin; xylan; biomass saccharification; structural analysis

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APA (6^th Edition):

Zhang, W. (2015). Biopolymer Structure Analysis and Saccharification of Glycerol Thermal Processed Biomass. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/71830

Chicago Manual of Style (16^th Edition):

Zhang, Wei. “Biopolymer Structure Analysis and Saccharification of Glycerol Thermal Processed Biomass.” 2015. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/71830.

MLA Handbook (7^th Edition):

Zhang, Wei. “Biopolymer Structure Analysis and Saccharification of Glycerol Thermal Processed Biomass.” 2015. Web. 22 Oct 2019.

Vancouver:

Zhang W. Biopolymer Structure Analysis and Saccharification of Glycerol Thermal Processed Biomass. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/71830.

Council of Science Editors:

Zhang W. Biopolymer Structure Analysis and Saccharification of Glycerol Thermal Processed Biomass. [Doctoral Dissertation]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/71830

Virginia Tech

20. Schoonover, Daniel Vernon. The Chemistry of Fullerenes, Polymers, and Host/Guest Interactions.

Degree: PhD, Chemistry, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/72841

► The exploitation of the relationship between the chemical and physical properties of materials is the hallmark of advancing science throughout the world. The basic understanding… (more)

▼ The exploitation of the relationship between the chemical and physical properties of materials is the hallmark of advancing science throughout the world. The basic understanding of how and why molecules react and interact with each other in different environments allows for the discovery and implementation of new materials and devices that not only advance the state of human life but continually change the planet. The work described in this dissertation generally falls under three diverse categories: functionalization of fullerenes, investigation of host/guest interactions in solution, and the synthesis and characterization of ion containing polymers. The separation and functionalization of fullerenes is a recent and exciting area of research. The separation methods outlined are intended to increase the availability of endohedral metallofullerenes by decreasing their cost of production. Functionalized fullerene species were achieved through Bingel and Prato reactions to provide materials with novel functional groups. These materials may be further utilized in photovoltaic or other organic electronic devices. The characterization of noncovalent interactions between different molecules in solution is the focus of supramolecular chemistry. Isothermal Titration Calorimetry stands out as one of the best, among the many methods used to elucidate the characteristics of these systems. The binding of bis- imidazolium and paraquat guests with macrocyclic host molecules has been explored in this work. The measurements of the association constants for these systems will aid in the ongoing synthesis of new host/guest systems. Ion containing polymers were synthesized and characterized for their use in electroactive devices. Imidazolium containing polymers with bulky anions were synthesized on low glass transition polymer chains. These materials had enhanced ion conductivity and may eventually be used in electronic actuator materials. Advisors/Committee Members: Gibson, Harry W. (committeechair), Esker, Alan R. (committee member), Gandour, Richard D. (committee member), Dorn, Harry C. (committee member).

Subjects/Keywords: fullerene; endohedral metallofullerene; host/guest; ionomer; polymer; purification; isothermal titration calorimetry; imidazolium; paraquat; cryptand; pseudorotaxane

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

APA (6^th Edition):

Schoonover, D. V. (2015). The Chemistry of Fullerenes, Polymers, and Host/Guest Interactions. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/72841

Chicago Manual of Style (16^th Edition):

Schoonover, Daniel Vernon. “The Chemistry of Fullerenes, Polymers, and Host/Guest Interactions.” 2015. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/72841.

MLA Handbook (7^th Edition):

Schoonover, Daniel Vernon. “The Chemistry of Fullerenes, Polymers, and Host/Guest Interactions.” 2015. Web. 22 Oct 2019.

Vancouver:

Schoonover DV. The Chemistry of Fullerenes, Polymers, and Host/Guest Interactions. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/72841.

Council of Science Editors:

Schoonover DV. The Chemistry of Fullerenes, Polymers, and Host/Guest Interactions. [Doctoral Dissertation]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/72841

Virginia Tech

21. Hudson, Amanda Gayle. Characterization of Intermolecular Interactions in Nanostructured Materials.

Degree: PhD, Chemistry, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/77855

► Advanced analytical techniques were utilized to investigate the intermolecular forces in several nanostructured materials. Techniques including, but not limited to, isothermal titration calorimetry (ITC), variable… (more)

▼ Advanced analytical techniques were utilized to investigate the intermolecular forces in several nanostructured materials. Techniques including, but not limited to, isothermal titration calorimetry (ITC), variable temperature Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-Vis) thermal curves were used to study the fundamental interactions present in various nanomaterials, and to further probe the influence of these interactions on the overall behavior of the material. The areas of focus included self-assembly of surfactant micelles, polycation complexation of DNA, and temperature-dependent hydrogen bonding in polymeric systems. ITC was successfully used to determine the low critical micelle concentration (CMC) for a novel gemini surfactant with limited water solubility. CMCs were measured at decreasing methanol molar fractions (xMeOH) in water and the resulting linear relationship between CMC and methanol concentration was used to mathematically extrapolate to a predicted CMC at xMeOH = 0. Using this technique, the CMC value for the novel gemini surfactant was predicted to be 0.037 ± 0.004 mM. This extrapolation technique was also validated with surfactant standards. ITC was also used to investigate the binding thermodynamics of polyplex formation with polycations and DNA. The imidazolium-containing and trehalose-based polycations were both found to have endothermic, entropically driven binding with DNA, while the adenine-containing polycation exhibited exothermic DNA binding. In addition, ITC was also used to confirm the stoichiometric binding ratio of linear polyethylenimine and DNA polyplexes as determined by a novel NMR method. Dynamic light scattering (DLS) and zeta potential measurements were also performed to determine the size and surface charge of polyplexes. Circular dichroism (CD) and FTIR spectroscopies provided information regarding the structural changes that may occur in the DNA upon complexation with polymers. UV-Vis thermal curves indicated that polyplexes exhibit a greater thermal stability than DNA by itself. Variable temperature FTIR spectroscopy was used to quantitatively compare the hydrogen bonding behavior of multi-walled carbon nanotube (MWCNT)-polyurethane composites. Spectra were collected from 35 to 185 deg C for samples containing various weight percent loadings of MWCNTs with different hydrogen bonding surface functionalities. Peak fitting analysis was performed in the carbonyl-stretching region for each sample, and the hydrogen-bonding index (Rindex) was reported. Rindex values were used to quantitatively compare all of the composite samples in regards to temperature effects, weight percent loadings of MWCNTs, and the different functionalizations. In general, higher weight percent loadings of the MWCNTs resulted in greater Rindex values and increased hydrogen bond dissociation temperatures. In addition, at 5 and 10 wt% loadings the initial Rindex values displayed a trend that tracked well with the increasing hydrogen bonding capacity of… Advisors/Committee Members: Moore, Robert Bowen (committeechair), Esker, Alan R. (committee member), Grove, Tijana (committee member), McNair, Harold M. (committee member).

Subjects/Keywords: isothermal titration calorimetry; variable temperature FTIR; surfactant; polymeric gene delivery; hydrogen bonding

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

APA (6^th Edition):

Hudson, A. G. (2015). Characterization of Intermolecular Interactions in Nanostructured Materials. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77855

Chicago Manual of Style (16^th Edition):

Hudson, Amanda Gayle. “Characterization of Intermolecular Interactions in Nanostructured Materials.” 2015. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/77855.

MLA Handbook (7^th Edition):

Hudson, Amanda Gayle. “Characterization of Intermolecular Interactions in Nanostructured Materials.” 2015. Web. 22 Oct 2019.

Vancouver:

Hudson AG. Characterization of Intermolecular Interactions in Nanostructured Materials. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/77855.

Council of Science Editors:

Hudson AG. Characterization of Intermolecular Interactions in Nanostructured Materials. [Doctoral Dissertation]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/77855

Virginia Tech

22. Carfagna Jr., Charles Samuel. Cyclopentadiene as a Platform for Polymer Synthesis and Modification of Macromolecular Systems.

Degree: PhD, Chemistry, 2015, Virginia Tech

URL: http://hdl.handle.net/10919/77870

► Octafluorobiphenylene-linked bis(cyclopentadienone) was prepared bearing one perfluoro-4-tolyl and one tert-butyl substituent on the terminal diene rings. Polymerizations with 1,4- and 1,3-diethynylbenzene afforded linear Diels-Alder polyphenylenes… (more)

▼ Octafluorobiphenylene-linked bis(cyclopentadienone) was prepared bearing one perfluoro-4-tolyl and one tert-butyl substituent on the terminal diene rings. Polymerizations with 1,4- and 1,3-diethynylbenzene afforded linear Diels-Alder polyphenylenes (DAPPs) having lateral tert-butyl and perfluoro-4-tolyl substituents. The perfluoro-4-tolyl-substituted DAPPs are thermally stable, glassy solids (Tg ~ 230 deg C) that could not be cast into stable films (Mn ~ 10kDa, DPn ~ 10). New compounds perfluoro(1-phenyl-1-octanone) and perfluoro(1,1-diphenyl-1-octanol) were prepared from pentafluorophenylmagnesium bromide and perfluorooctanoyl chloride by nucleophilic acyl substitution and addition reactions. Diels-Alder reactions of 1,2-bis(nonafluorobiphenyl-4-yl)-4-tert-butylcyclopentadiene (CPD-1) with N-(4-fluorophenyl)maleimide (FMI) were explored as models for cyclopentadiene-maleimide-based Diels-Alder polymerizations. Mixtures of five endo/exo adducts were obtained, dependent upon CPD-1 tautomers present at reaction temperatures. The thermodynamic adduct (B3LYP/6-31G* geometry optimizations) was found to be the exo DA adduct of FMI and 2,3-bis(nonafluorobiphenyl-4-yl)-5-tert-butylcyclopentadiene. Five of the six possible isomers were observed and characterized including two by single-crystal X-ray diffraction. Parallel reactions of FMI and 1,2-bis(pentafluorophenyl)-4-tert-butylcyclopentadiene yielded three crystallographically characterized isomers, and with 1H NMR and 19F NMR spectrometry, including 1-D NOE, allowed five isomeric products to be identified. Diene CPD-1 is reactive toward nucleophiles (such as potassium 4-methylphenoxide) at the 4-positions of the C12F9 groups. Using this reactivity pattern, CPD-1 was polymerized with bis(phenol) A (BPA) and bis(phenol-A-6F) (BPAF) to form linear poly(arylene ethers) (Mn ~35 kDa) containing backbone cyclopentadienes. These polymers are glassy solids (Tg ~ 220 deg C) with good thermal stability (Td ~ 290 deg C), and they form stable, creaseable films cast from chloroform solutions. Treatment with 1.5-5.0% of 1,6-bis(N-maleimido)dodecane in N,N-dimethylacetamide (DMAc) at 165 deg C gave insoluble, solvent-swellable networks confirmed using ATR-FTIR. CPD-1 was also used as a cyclopentadiene-based linking group for chain extension of phenol-terminated methyl-PEEK oligomers (PEEKMOHs) with Mn values of 2, 5, and 10 kDa. These polymers are glassy solids (Tg ~ 156 deg C) with good thermal stability (Td ~ 400 deg C), that form stable, creaseable films from chloroform. Segmented polymers were treated with FMI in NMP, and showed functionalization density of approximately 50% by 19F NMR. Segmented polymers were also cross-linked by reaction of 1,6-bis(N-maleimido)hexane (cyclopentadiene to maleimide functional group ratio of 1:1) in NMP at 140 deg C. Advisors/Committee Members: Deck, Paul A. (committeechair), Hanson, Brian Ernest (committee member), Esker, Alan R. (committee member), Gibson, Harry W. (committee member).

Subjects/Keywords: Diels-Alder; cyclopentadiene; maleimide; PEEKMOH; telechelic; step-growth polymerization; polymer functionalization

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APA (6^th Edition):

Carfagna Jr., C. S. (2015). Cyclopentadiene as a Platform for Polymer Synthesis and Modification of Macromolecular Systems. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77870

Chicago Manual of Style (16^th Edition):

Carfagna Jr., Charles Samuel. “Cyclopentadiene as a Platform for Polymer Synthesis and Modification of Macromolecular Systems.” 2015. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/77870.

MLA Handbook (7^th Edition):

Carfagna Jr., Charles Samuel. “Cyclopentadiene as a Platform for Polymer Synthesis and Modification of Macromolecular Systems.” 2015. Web. 22 Oct 2019.

Vancouver:

Carfagna Jr. CS. Cyclopentadiene as a Platform for Polymer Synthesis and Modification of Macromolecular Systems. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/77870.

Council of Science Editors:

Carfagna Jr. CS. Cyclopentadiene as a Platform for Polymer Synthesis and Modification of Macromolecular Systems. [Doctoral Dissertation]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/77870

Virginia Tech

23. Pan, Lei. Surface and Hydrodynamic Forces in Wetting Films.

Degree: PhD, Mining and Minerals Engineering, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/51538

► The process of froth flotation relies on using air bubbles to collect desired mineral particles dispersed in aqueous media on the surface, while leaving undesirous… (more)

▼ The process of froth flotation relies on using air bubbles to collect desired mineral particles dispersed in aqueous media on the surface, while leaving undesirous mineral particles behind. For a particle to be collected on the surface of a bubble, the thin liquid films (or wetting films) of water formed in between must rupture. According to the Frumkin-Derjaguin isotherm, it is necessary that wetting films can rupture when the disjoining pressures are negative. However, the negative disjoining pressures are difficult to measure due to the instability and short lifetimes of the films. In the present work, two new methods of determining negative disjoining pressures have been developed. One is to use the modified thin film pressure balance (TFPB) technique, and the other is to directly determine the interaction forces using the force apparatus for deformable surfaces (FADS) developed in the present work. The former is designed to obtain spatiotemporal profiles of unstable wetting films by recording the optical interference patterns. The kinetic information derived from the spatiotemporal profiles were then used to determine the disjoining pressures using an analytical expression derived in the present work on the basis of the Reynolds lubrication theory. The technique has been used to study the effects of surface hydrophobicity, electrolyte (Al3+ ions) concentration, and bubble size on the stability of wetting films. Further, the geometric mean combining rule has been tested to see if the disjoining pressures of the wetting films can be predicted from the disjoining pressures of the colloid films formed between two hydrophobic surfaces and the disjoining pressures of the foam films formed between two air bubbles. The FADS is capable of directly measuring the interaction forces between air bubble and solid surface, and simultaneously monitoring the bubble deformation. The results were analyzed using the Reynolds lubrication theory and the extended DLVO theory to determine both the hydrodynamic and disjoining pressures. The FADS was used to study the effects of surface hydrophobicity and approach speeds. The results show that hydrophobic force is the major driving force for the bubble-particle interactions occurring in flotation. Advisors/Committee Members: Yoon, Roe-Hoan (committeechair), Luttrell, Gerald H. (committee member), Jung, Sunghwan (committee member), Adel, Gregory T. (committee member), Esker, Alan R. (committee member).

Subjects/Keywords: wetting film; hydrophobic force; hydrodynamic force; force apparatus for deformable surfaces (FADS); Frumkin-Derjaguin isotherm

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APA (6^th Edition):

Pan, L. (2013). Surface and Hydrodynamic Forces in Wetting Films. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/51538

Chicago Manual of Style (16^th Edition):

Pan, Lei. “Surface and Hydrodynamic Forces in Wetting Films.” 2013. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/51538.

MLA Handbook (7^th Edition):

Pan, Lei. “Surface and Hydrodynamic Forces in Wetting Films.” 2013. Web. 22 Oct 2019.

Vancouver:

Pan L. Surface and Hydrodynamic Forces in Wetting Films. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/51538.

Council of Science Editors:

Pan L. Surface and Hydrodynamic Forces in Wetting Films. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/51538

Virginia Tech

24. Zhou, Xu. Synthesis and Characterization of Nanoporous Copolymers with Potential Gas Storage Applications.

Degree: PhD, Chemistry, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/51669

► Nanoporous organic polymers, including hypercrosslinked polymers (HCPs), covalent organic frameworks (COFs), polymers of intrinsic microporosity (PIMs), and conjugated microporous polymers (CMPs) etc., are considered good… (more)

▼ Nanoporous organic polymers, including hypercrosslinked polymers (HCPs), covalent organic frameworks (COFs), polymers of intrinsic microporosity (PIMs), and conjugated microporous polymers (CMPs) etc., are considered good candidates for potential gas storage and gas separation applications. Porosities and surface areas of a series of semirigid alternating copolymers, which contained tert-butyl carboxylate-functionalized stilbene or tert-butyl carboxylate-functionalized styrene, and maleic anhydride or tert-butyl carboxylate-functionalized phenyl maleimide, were investigated using nitrogen sorption/desorption isotherms at 77 K and molecular simulations. These alternating copolymers were found to have Brunauer-Emmett-Teller (BET) surface areas in the range of 20-40 m2/g. Surface areas of these alternating copolymers increased as the steric crowding of the polymer backbone increased, which was the result of introducing extra phenyl rings and/or N-phenyl substituent maleimide units. Surface areas were found to increase as the persistence length increased. A series of HCPs containing functionalized stilbene and N-substituted phenyl maleimide were synthesized via free radical suspension polymerization. The incorporation of these functionalized, chain stiffening, Tg enhancing comonomers raised the Tgs of precursor polymers before they were crosslinked. Surface areas of these HCPs, obtained from nitrogen adsorption/desorption isotherms at 77 K, were up to 1058 m2/g. However, the surface areas of these HCPs were systematically lower than the controls. The high rigidity of the polymer backbone, which was the result of incorporating Tg enhancing comonomer, likely affected the chain mobility of the precursor polymer, decreased the efficiency of post-crosslinking reactions, and thus resulted in lower surface areas. Amine-functionalized styrene/stilbene polymers were prepared via free radical polymerization or post-modification. Amine-containing silica-based sorbents were prepared using the impregnation method. Sorption of CO2 by these materials was tested using TGA and compared with control samples. Both high amine content and certain levels of surface area were found to be important for a sorbent to achieve high CO2 uptake. Highest CO2 uptake (12 wt%) under our testing condition in these materials was achieved by an amine-containing silica sorbent. Advisors/Committee Members: Turner, Sam Richard (committeechair), Gibson, Harry W. (committee member), Gandour, Richard D. (committee member), Esker, Alan R. (committee member).

Subjects/Keywords: nanoporous polymer; semirigid alternating copolymer; gas sorption; surface area; functionalized stilbene; functionalized maleimide; hypercrosslinked polymer; suspension polymerization; free radical polymerization; mesoporous silica; CO2 capture

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

APA (6^th Edition):

Zhou, X. (2013). Synthesis and Characterization of Nanoporous Copolymers with Potential Gas Storage Applications. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/51669

Chicago Manual of Style (16^th Edition):

Zhou, Xu. “Synthesis and Characterization of Nanoporous Copolymers with Potential Gas Storage Applications.” 2013. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/51669.

MLA Handbook (7^th Edition):

Zhou, Xu. “Synthesis and Characterization of Nanoporous Copolymers with Potential Gas Storage Applications.” 2013. Web. 22 Oct 2019.

Vancouver:

Zhou X. Synthesis and Characterization of Nanoporous Copolymers with Potential Gas Storage Applications. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/51669.

Council of Science Editors:

Zhou X. Synthesis and Characterization of Nanoporous Copolymers with Potential Gas Storage Applications. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/51669

Virginia Tech

25. Zhang, Xiao. Adsorption of Biomacromolecules onto Polysaccharide Surfaces.

Degree: PhD, Chemistry, 2014, Virginia Tech

URL: http://hdl.handle.net/10919/52574

► Plant cell wall polysaccharides are abundant natural polymers making them potential sources for sustainable and biodegradable materials. Interfacial behavior, including adsorption and enzymatic degradation, of… (more)

▼ Plant cell wall polysaccharides are abundant natural polymers making them potential sources for sustainable and biodegradable materials. Interfacial behavior, including adsorption and enzymatic degradation, of several plant cell wall polysaccharides and their derivatives were studied with a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM). Xyloglucan adsorption isotherms were obtained to probe how cellulose-hemicellulose interactions were affected by the type of cellulose substrate and molar mass of xyloglucan. Xyloglucan as small as a heptasaccharide still adsorbed irreversibly onto cellulose. Carboxymethyl cellulose (CMC) adsorption onto cellulose and viscoelastic properties and water contents of the adsorbed CMC layers were obtained from a combination of QCM-D and SPR data. The CMC samples formed hydrated and viscoelastic layers compared to the relatively rigid xyloglucan layer. Pectin model surfaces were prepared by pectin adsorption from citric phosphate buffer onto gold substrates. These pectin model surfaces were used for subsequent interaction studies with xyloglucan and enzymatic degradation behavior. There is a strong correlation between the degree of esterification (DE) and film resistance to degradation with the high DE being the most susceptible to degradation. The adsorption of two mixed linkage glucans (MLG), barley and lichen MLG, onto regenerated cellulose (RC) surfaces in the absence and presence of other matrix polysaccharides was studied. Viscoelastic properties of the resulting layer were compared as a function of the proprotion of '-(1''3) linkages with lichen MLG forming softer gel-like layers on RC. The lichen MLG layers were further used for enzymatic degradation studies with respect to enzyme concentration, temperature, pH and ionic strength. These studies show that polymer adsorption is a promising strategy to modify material surfaces and provides fundamental understanding of interactions and biodegradation of cell wall polysaccharides at solid/liquid interfaces. Advisors/Committee Members: Esker, Alan R. (committeechair), Marand, Herve (committee member), Roman, Maren (committee member), Edgar, Kevin J. (committee member), Madsen, Louis A. (committee member).

Subjects/Keywords: Quartz Crystal Microbalance with Dissipation Monitoring; Surface Plasmon Resonance; Cellulose; Carboxymethyl Cellulose; Pectin and Mixed Linkage Glucans

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APA (6^th Edition):

Zhang, X. (2014). Adsorption of Biomacromolecules onto Polysaccharide Surfaces. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/52574

Chicago Manual of Style (16^th Edition):

Zhang, Xiao. “Adsorption of Biomacromolecules onto Polysaccharide Surfaces.” 2014. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/52574.

MLA Handbook (7^th Edition):

Zhang, Xiao. “Adsorption of Biomacromolecules onto Polysaccharide Surfaces.” 2014. Web. 22 Oct 2019.

Vancouver:

Zhang X. Adsorption of Biomacromolecules onto Polysaccharide Surfaces. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/52574.

Council of Science Editors:

Zhang X. Adsorption of Biomacromolecules onto Polysaccharide Surfaces. [Doctoral Dissertation]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/52574

Virginia Tech

26. Sheth, Swapnil Suhas. Self-Consistency of the Lauritzen-Hoffman and Strobl Models of Polymer Crystallization Evaluated for Poly(ε-caprolactone) Fractions and Effect of Composition on the Phenomenon of Concurrent Crystallization in Polyethylene Blends.

Degree: PhD, Chemistry, 2013, Virginia Tech

URL: http://hdl.handle.net/10919/23904

► Narrow molecular weight fractions of Poly(ε-caprolactone) were successfully obtained using the successive precipitation fractionation technique with toluene/n-heptane as a solvent/nonsolvent pair. Calorimetric studies of the… (more)

▼ Narrow molecular weight fractions of Poly(ε-caprolactone) were successfully obtained using the successive precipitation fractionation technique with toluene/n-heptane as a solvent/nonsolvent pair. Calorimetric studies of the melting behavior of fractions that were crystallized either isothermally or under constant cooling rate conditions suggested that the isothermal crystallization of the samples should be used for a proper evaluation of the molecular weight dependence of the observed melting temperature and degree of crystallinity in PCL. The molecular weight and temperature dependence of the spherulitic growth rate of fractions was studied in the context of the Lauritzen-Hoffman two-phase model and the Strobl three-phase model of polymer crystallization. The zero-growth rate temperatures, determined from spherulitic growth rates using four different methods, are consistent with each other and increase with chain length. The concomitant increase in the apparent secondary nucleation constant was attributed to two factors. First, for longer chains there is an increase in the probability that crystalline stems belong to loose chain-folds, hence, an increase in fold surface free energy. It is speculated that the increase in loose folding and resulting decrease in crystallinity with increasing chain length are associated with the ester group registration requirement in PCL crystals. The second contribution to the apparent nucleation constant arises from chain friction associated with segmental transport across the melt/crystal interface. These factors were responsible for the much stronger chain length dependence of spherulitic growth rates at fixed undercooling observed here with PCL than previously reported for PE and PEO. In the case of PCL, the scaling exponent associated with the chain length dependence of spherulitic growth rates exceeds the upper theoretical bound of 2 predicted from the Brochard-DeGennes chain pullout model. Observation that zero-growth and equilibrium melting temperature values are identical with each other within the uncertainty of their determinations casts serious doubt on the validity of Strobl three-phase model. A novel method is proposed to determine the Porod constant necessary to extrapolate the small angle X-ray scattering intensity data to large scattering vectors. The one-dimensional correlation function determined using this Porod constant yielded the values of lamellar crystal thickness, which were similar to these estimated using the Hosemann-Bagchi Paracrystalline Lattice model. The temperature dependence of the lamellar crystal thickness was consistent with both LH and the Strobl model of polymer crystallization. However, in contrast to the predictions of Strobl’s model, the value of the mesomorph-to-crystal equilibrium transition temperature was very close to the zero-growth temperature. Moreover, the lateral block sizes (obtained using wide angle X-ray diffraction) and the lamellar thicknesses were not found to be controlled by the mesomorph-to-crystal equilibrium… Advisors/Committee Members: Marand, Hervé L. (committeechair), Moore, Robert Bowen (committee member), Esker, Alan R. (committee member), Turner, Sam Richard (committee member).

Subjects/Keywords: Polymer Crystallization; Poly(ε-caprolactone); Lauritzen-Hoffman Model; Strobl Model; Fractionation; Spherulite Growth Rate; Brochard-deGennes Theory; Lamellar Thickness; X-ray Scattering; Concurrent Crystallization; Co-crystallization

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

APA (6^th Edition):

Sheth, S. S. (2013). Self-Consistency of the Lauritzen-Hoffman and Strobl Models of Polymer Crystallization Evaluated for Poly(ε-caprolactone) Fractions and Effect of Composition on the Phenomenon of Concurrent Crystallization in Polyethylene Blends. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/23904

Chicago Manual of Style (16^th Edition):

Sheth, Swapnil Suhas. “Self-Consistency of the Lauritzen-Hoffman and Strobl Models of Polymer Crystallization Evaluated for Poly(ε-caprolactone) Fractions and Effect of Composition on the Phenomenon of Concurrent Crystallization in Polyethylene Blends.” 2013. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/23904.

MLA Handbook (7^th Edition):

Sheth, Swapnil Suhas. “Self-Consistency of the Lauritzen-Hoffman and Strobl Models of Polymer Crystallization Evaluated for Poly(ε-caprolactone) Fractions and Effect of Composition on the Phenomenon of Concurrent Crystallization in Polyethylene Blends.” 2013. Web. 22 Oct 2019.

Vancouver:

Sheth SS. Self-Consistency of the Lauritzen-Hoffman and Strobl Models of Polymer Crystallization Evaluated for Poly(ε-caprolactone) Fractions and Effect of Composition on the Phenomenon of Concurrent Crystallization in Polyethylene Blends. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/23904.

Council of Science Editors:

Sheth SS. Self-Consistency of the Lauritzen-Hoffman and Strobl Models of Polymer Crystallization Evaluated for Poly(ε-caprolactone) Fractions and Effect of Composition on the Phenomenon of Concurrent Crystallization in Polyethylene Blends. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/23904

Virginia Tech

27. Geng, Xi. Bioenabled Synthesis of Anisotropic Gold and Silver Nanoparticles.

Degree: PhD, Chemistry, 2017, Virginia Tech

URL: http://hdl.handle.net/10919/86274

► Anisotropic plasmonic noble metallic nanoparticles (APMNs) have received enormous attention due to their distinct geometric features and fascinating physicochemical properties. Owing in large part to… (more)

▼ Anisotropic plasmonic noble metallic nanoparticles (APMNs) have received enormous attention due to their distinct geometric features and fascinating physicochemical properties. Owing in large part to their tailored localized surface plasmon resonance (LSPR) and the intensive electromagnetic field at the sharp corners and edges, APMNs are exceptionally well suited for biomedical applications such as biosensing, bioimaging, diagnostics and therapeutics. Although a rich variety of surfactant-assisted colloidal routes have been developed to prepare well-defined APMNs, biomedical applications necessitate tedious and rigorous purification processes for the complete removal of toxic surfactants. In this dissertation, we aim to develop generic bioenabled green synthetic methodologies towards APMNs. By applying a series of thermodynamic, kinetic and seed quality control, a series of APMNs with varied morphologies such as branched nanostars and triangular nanoprisms have been successfully prepared. We first presented the preparation of gold nanostars (Au NSTs) through a two-step approach utilizing a common Good's buffer, HEPES, as a weak reducing agent. Single crystalline Au NSTs with tunable branches up to 30 nm in length were produced and the halide ions rather than the ionic strength played a significant roles on the length of the branches of Au NSTs. Then consensus sequence tetratricopetide repeat (CTPR) proteins with increasing number of repeats were used as model proteins to probe the effects of concentration as well as the protein shape on the morphology and resulting physicochemical properties of plasmonic gold nanoparticles. Since the underlying growth mechanism for the biomimetic synthesis of APMNs remains elusive and controversial, the other objective is to elucidate the molecular interactions between inorganic species and biopolymers during the course of NP evolution. Fluorescent quenching and 2D NMR experiments have confirmed the moderate binding affinity of CTPR to the Au(0) and Au(III). We observed that the initial complexation step between gold ions and CTPR3 is ionic strength dependent. Furthermore, we also found that NPs preferentially interact with the negatively charged face of CTPR3 as observed in 2D NMR. Knowledge of binding behavior between biospecies and metal ions/NPs will facilitate rational deign of proteins for biomimetic synthesis of metallic NPs. A modified seed-mediated synthetic strategy was also developed for the growth of silver nanoprisms with low shape polydispersity, narrow size distribution and tailored plasmonic absorbance. During the seed nucleation step, CTPR proteins are utilized as potent stabilizers to facilitate the formation of planar-twinned Ag seeds. Ag nanoprisms were produced in high yield in a growth solution containing ascorbic acid and CTPR-stabilized Ag seeds. From the time-course UV-Vis and transmission electron microscopy (TEM) studies, we postulate that the growth mechanism is the combination of facet selective lateral growth and thermodynamically driven Ostwald… Advisors/Committee Members: Grove, Tijana (committeechair), Esker, Alan R. (committee member), Morris, John R. (committee member), Moore, Robert Bowen (committee member).

Subjects/Keywords: plasmonic; localized surface plasmon resonance (LSPR); anisotropic nanoparticles; bioenabled synthesis; nanoprisms; nanostars; SERS; repeat protein; lignin.

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APA (6^th Edition):

Geng, X. (2017). Bioenabled Synthesis of Anisotropic Gold and Silver Nanoparticles. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/86274

Chicago Manual of Style (16^th Edition):

Geng, Xi. “Bioenabled Synthesis of Anisotropic Gold and Silver Nanoparticles.” 2017. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/86274.

MLA Handbook (7^th Edition):

Geng, Xi. “Bioenabled Synthesis of Anisotropic Gold and Silver Nanoparticles.” 2017. Web. 22 Oct 2019.

Vancouver:

Geng X. Bioenabled Synthesis of Anisotropic Gold and Silver Nanoparticles. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/86274.

Council of Science Editors:

Geng X. Bioenabled Synthesis of Anisotropic Gold and Silver Nanoparticles. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/86274

Virginia Tech

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

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 October 22, 2019. 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. 22 Oct 2019.

Vancouver:

Beach J. Preparation and Electrochemical Testing of Flexible Carbon Nanofiber Electrodes from Electrospinning. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2019 Oct 22]. 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

29. Huang, Jing. Functional Polymers Containing Semi-Rigid Alternating Sequences.

Degree: PhD, Chemistry, 2017, Virginia Tech

URL: http://hdl.handle.net/10919/89884

► Alternating copolymers represent a special class of copolymers in which the two comonomers copolymerize in a regular alternating sequence along the polymer chain. Of particular… (more)

▼ Alternating copolymers represent a special class of copolymers in which the two comonomers copolymerize in a regular alternating sequence along the polymer chain. Of particular interest in our group are the stilbene-maleic anhydride/maleimide alternating copolymers. These copolymers possess sterically congested backbones and precisely placed functional groups arising from the strictly alternating copolymerization. The research in this dissertation is focused on the synthesis, characterization, and potential application of functionalized copolymers that contain semi-rigid alternating copolymer sequences. The fluorescence properties of a series of non-conjugated, tert-butyl carboxylate functionalized alternating copolymers were investigated. Extraordinarily high fluorescent intensity with excellent linearity was observed for the di-tert-butyl group-containing stilbene and maleic anhydride alternating copolymer in THF. We attributed the origin of the strong fluorescence to the “through space” π – π interactions between the phenyl rings from the stilbene and C=O groups from the anhydride. The fluorescence was maintained when the copolymer was deprotected and hydrolyzed and the resulting carboxylic acid-functionalized copolymer was dissolved in water at neutral pH. The tert-butyl carboxylate functionalized alternating copolymer sequences were incorporated into highly crosslinked polymer networks using suspension polymerization. After removing the tert-butyl groups by acidic hydrolysis, the surface area of the networks increased significantly. Using this facile two-step strategy, we were able to achieve nanoporous polymers with BET surface area up to 817 m2/g and carboxylic acid-functionalized surfaces. The BET surface area of deprotected polymers increased with increasing crosslinking density, and the stilbene-containing polymers showed systematically higher BET surface area than the styrene-containing polymers due to the stiffness of the alternating sequences. The resulting nanoporous polymers have potential to be employed as solid sorbents for CO2. The same tert-butyl carboxylate functionalized alternating copolymer sequences were also incorporated into microgels via miniemulsion polymerization. The miniemulsion technique ensured the successful synthesis of microgels with ~100 nm diameter using solid stilbene and maleimide monomers. The resulting tert-butyl carboxylate-containing microgels were converted into carboxylic acid-containing aqueous microgels by acid hydrolysis. These aqueous microgels showed good and reversible lead and copper ion adsorption capacities. Amine-functionalized nanoporous polymers were synthesized by the post-modification of highly-crosslinked divinylbenzene-maleic anhydride polymers. High amine-contents were achieved by covalently attaching multiamines to the acid-chloride functionalized polymer surface. The resulting polymers showed medium to high BET surface areas (up to 500 m2/g) and high CO2 capture capacities. Advisors/Committee Members: Turner, Sam Richard (committeechair), Matson, John (committee member), Gandour, Richard D (committee member), Esker, Alan R (committee member).

Subjects/Keywords: alternating copolymers; hypercrosslinked polymers; microgels; CO2 adsorption; fluorescence; heavy metal ion adsorption

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

APA (6^th Edition):

Huang, J. (2017). Functional Polymers Containing Semi-Rigid Alternating Sequences. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/89884

Chicago Manual of Style (16^th Edition):

Huang, Jing. “Functional Polymers Containing Semi-Rigid Alternating Sequences.” 2017. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/89884.

MLA Handbook (7^th Edition):

Huang, Jing. “Functional Polymers Containing Semi-Rigid Alternating Sequences.” 2017. Web. 22 Oct 2019.

Vancouver:

Huang J. Functional Polymers Containing Semi-Rigid Alternating Sequences. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/89884.

Council of Science Editors:

Huang J. Functional Polymers Containing Semi-Rigid Alternating Sequences. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/89884

Virginia Tech

30. McCord, Jennifer Phipps. Protein Engineering for Biomedicine and Beyond.

Degree: PhD, Chemistry, 2019, Virginia Tech

URL: http://hdl.handle.net/10919/90787

► Many applications in biomedicine, research, and industry require recognition agents with specificity and selectivity for their target. Protein engineering enables the design of scaffolds that… (more)

▼ Many applications in biomedicine, research, and industry require recognition agents with specificity and selectivity for their target. Protein engineering enables the design of scaffolds that can bind targets of interest while increasing their stability, and expanding the scope of applications in which these scaffolds will be useful. Repeat proteins are instrumental in a wide variety of biological processes, including the recognition of pathogen-associated molecular patterns by the immune system. A number of successes using alternative immune system repeat protein scaffolds have expanded the scope of recognition agents available for targeting glycans and glycoproteins in particular. We have analyzed the innate immune genes of a freshwater polyp and found that they contained particularly long contiguous domains with high sequence similarity between repeats in these domains. We undertook statistical design to create a binding protein based on the H. magnipapillata innate immune TPR proteins. My second research project focused on creating a protein to bind cellulose, as it is the most abundant and inexpensive source of biomass and therefore is widely considered a possible source for liquid fuel. However, processing costs have kept lignocellulosic fuels from competing commercially with starch-based biofuels. In recent years a strategy to protect processing enzymes with synergistic proteins emerged to reduce the amount of enzyme necessary for lignocellulosic biofuel production. Simultaneously, protein engineering approaches have been developed to optimize proteins for function and stability enabling the use of proteins under non-native conditions and the unique conditions required for any necessary application. We designed a consensus protein based on the carbohydrate-binding protein domain CBM1 that will bind to cellulosic materials. The resulting designed protein is a stable monomeric protein that binds to both microcrystalline cellulose and amorphous regenerated cellulose thin films. By studying small changes to the binding site, we can better understand how these proteins bind to different cellulose-based materials in nature and how to apply their use to industrial applications such as enhancing the saccharification of lignocellulosic feedstock for biofuel production. Biomaterials made from natural human hair keratin have mechanical and biochemical properties that make them ideal scaffolds for tissue engineering and wound healing. However, the extraction process leads to protein degradation and brings with it byproducts from hair, which can cause unfavorable immune responses. Recombinant keratin biomaterials are free from these disadvantages, while heterologous expression of these proteins allows us to manipulate the primary sequence. We endeavored to add an RGD sequence to facilitate cell adhesion to the recombinant keratin proteins, to demonstrate an example of useful sequence modification. Advisors/Committee Members: Grove, Tijana (committeechair), Etzkorn, Felicia A. (committee member), Van Dyke, Mark (committee member), Esker, Alan R. (committee member).

Subjects/Keywords: protein engineering; consensus design; repeat proteins; cellulose binding module; keratin

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

APA (6^th Edition):

McCord, J. P. (2019). Protein Engineering for Biomedicine and Beyond. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/90787

Chicago Manual of Style (16^th Edition):

McCord, Jennifer Phipps. “Protein Engineering for Biomedicine and Beyond.” 2019. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/90787.

MLA Handbook (7^th Edition):

McCord, Jennifer Phipps. “Protein Engineering for Biomedicine and Beyond.” 2019. Web. 22 Oct 2019.

Vancouver:

McCord JP. Protein Engineering for Biomedicine and Beyond. [Internet] [Doctoral dissertation]. Virginia Tech; 2019. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/90787.

Council of Science Editors:

McCord JP. Protein Engineering for Biomedicine and Beyond. [Doctoral Dissertation]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/90787

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