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Articles 1 - 11 of 11
Full-Text Articles in Engineering
Bottom-Up Morphological Control Of Biphasic Polymer Particles Via Heterogeneous Polymerization, Heather S.C. Hamilton
Bottom-Up Morphological Control Of Biphasic Polymer Particles Via Heterogeneous Polymerization, Heather S.C. Hamilton
Doctoral Dissertations
Heterogeneous polymerization techniques are industrially relevant, scalable methods to synthesize polymer colloids and they have emerged in recent decades as viable methods to produce biphasic and morphologically complex polymer particles. The overarching goal of this thesis is to understand how heterogeneous polymerization techniques can be modified and optimized to control particle morphology through the systematic study of process parameters. Chapter 1 introduces relevant nomenclature and provides a brief historical perspective on the development of heterogeneous polymerization. This chapter also reviews the state-of-the-art techniques used to prepare morphologically complex polymer particles, with an emphasis on the heterogeneous polymerization processes studied in …
Electrospinning Fibers Via Complex Coacervation, Xiangxi Meng
Electrospinning Fibers Via Complex Coacervation, Xiangxi Meng
Doctoral Dissertations
Electrospun fibers are high-surface-area materials widely used in applications ranging from batteries to wound dressings. Typically, an electrospinning precursor solution is prepared by dissolving a high-molecular-weight polymer in an organic solvent to form a sufficiently entangled solution. Our approach bypasses the requirement for entanglements and completely avoids toxic chemicals by focusing on using an aqueous complex coacervates solution. Coacervates are a dense, polymer-rich liquid phase resulting from the associative electrostatic complexation of oppositely charged macroions. We were the first to demonstrate that liquid complex coacervates could be successfully electrospun into polyelectrolyte complex (PEC) fibers. A canonical coacervate system was formed …
Sequence And Entropy-Based Control Of Complex Coacervates, Li-Wei Chang, Tyler K. Lytle, Mithun Radhakrishna, Joel J. Madinya, Jon Vélez, Charles E. Sing, Sarah L. Perry
Sequence And Entropy-Based Control Of Complex Coacervates, Li-Wei Chang, Tyler K. Lytle, Mithun Radhakrishna, Joel J. Madinya, Jon Vélez, Charles E. Sing, Sarah L. Perry
Chemical Engineering Faculty Publication Series
Biomacromolecules rely on the precise placement of monomers to encode information for structure, function, and physiology. Efforts to emulate this complexity via the synthetic control of chemical sequence in polymers are finding success; however, there is little understanding of how to translate monomer sequence to physical material properties. Here we establish design rules for implementing this sequence-control in materials known as complex coacervates. These materials are formed by the associative phase separation of oppositely charged polyelectrolytes into polyelectrolyte dense (coacervate) and polyelectrolyte dilute (supernatant) phases. We demonstrate that patterns of charges can profoundly affect the charge–charge associations that drive this …
Kinetics And Dynamics Of Electrophoretic Translocation Of Polyelectrolytes Through Nanopores, Harshwardhan Katkar
Kinetics And Dynamics Of Electrophoretic Translocation Of Polyelectrolytes Through Nanopores, Harshwardhan Katkar
Doctoral Dissertations
The idea of sequencing a DNA based on single-file translocation of the DNA through nanopores under the action of an electric field has received much attention over the past two decades due to the societal need for low cost and high-throughput sequencing. However, due to the high speed of translocation, interrogating individual bases with an acceptable signal to noise ratio as they traverse the pore has been a major problem. Experimental facts on this phenomenon are rich and the associated phenomenology is yet to be fully understood. This thesis focuses on understanding the underlying principles of polymer translocation, with an …
Engineering Polymers Through Impact Modification And Superheated Liquid Processing, Gregory Connor Evans
Engineering Polymers Through Impact Modification And Superheated Liquid Processing, Gregory Connor Evans
Doctoral Dissertations
A new approach to toughen anionically polymerized polyamide 6 (aPA6) was applied using reaction induced phase separation (RIPS). This method solved issues with particle dispersion, mixture viscosity, and additive concentration common with conventional rubber toughening thereby making it an ideal candidate for fiber reinforced aPA6 reaction injection molding (RIM). Octamethylcyclotetrasiloxane (D4) was used as a functional additive that undergoes RIPS during aPA6 polymerization and polymerizes to polydimethylsiloxane (PDMS). Controlled phase separation, modulus retention, and increased crystallinity were achieved at low additive concentrations. Optimal properties were achieved with 2 wt% D4. Fracture energy was measured at high …
Ultra-Thin Polymer Films And Hierarchical Composites: Processing And Mechanical Properties, Yujie Liu
Ultra-Thin Polymer Films And Hierarchical Composites: Processing And Mechanical Properties, Yujie Liu
Doctoral Dissertations
Properties and fabrications of ultra-thin polymer films and hierarchical composites are of great interest in packaging, electronics, separations, and other manufacturing fields. However, due to the inherently fragile nature of ultra-thin polymer films, measuring their properties has proven difficult. Additionally, variables controlling thin polymer patterns (e.g. substrate wetting property) and composites (weight percent of particulates in matrix) formation have not been fundamentally well understood. Within this spectrum, fundamental understanding of formation mechanisms of these patterns and composites are needed. Additionally, a new characterization technique is required to be able to measure the mechanical properties of fabricated composites and thin films. …
Tailoring Nanoparticles And Polymers For Cooperative Interfacial And Surface Interactions, Irem Bolukbasi
Tailoring Nanoparticles And Polymers For Cooperative Interfacial And Surface Interactions, Irem Bolukbasi
Doctoral Dissertations
This thesis describes the synthesis of chemically functionalized nanoparticles and their behavior at interfaces and in conjunction with polymers. Solid-liquid, liquid-liquid, and air-liquid interfaces are useful platforms for studying nanoparticle assembly, especially when nanoparticles are functionalized to enable their segregation to the interface. At the liquid-liquid interface, double emulsions droplets, both oil-in-water-in-oil and water-in-oil-in-water, stabilized with nanoparticles were prepared. This involved gold nanoparticles stabilizing oil-in-water droplets, and CdSe quantum dots stabilizing water-in-oil droplets. These double emulsion droplets were by simply shaking to give polydisperse droplets, or in a well-defined fashion by microcapillary flow focusing. When nanoparticle-stabilized double emulsions were sized …
On The Effect Of Elasticity On Drag Reduction Due To Polymer Additives Using A Hybrid D.N.S. And Langevin Dynamics Approach, Arnout Boelens
On The Effect Of Elasticity On Drag Reduction Due To Polymer Additives Using A Hybrid D.N.S. And Langevin Dynamics Approach, Arnout Boelens
Open Access Dissertations
In this work the effect of elasticity on turbulent drag reduction due to polymers is investigated using a hybrid Direct Numerical Simulation (D.N.S) and Langevin dynamics approach. Simulations are run at a friction Reynolds number of Re_&tau = 560 for 960.000 dumbbells with Deborah numbers of De = 0, De = 1, and De = 10. The conclusions are that it is possible to simulate a drag reduced flow using hybrid D.N.S. with Langevin dynamics, that polymers, like other occurrences of drag reduction, reduce drag through streak stabilization, and that the essential property of polymers and fibers in having a …
Developing Reactive Molecular Dynamics For Understanding Polymer Chemical Kinetics, Kenneth D. Smith
Developing Reactive Molecular Dynamics For Understanding Polymer Chemical Kinetics, Kenneth D. Smith
Open Access Dissertations
One of the challenges in understanding polymer flammability is the lack of information about microscopic events that lead to macroscopically observed species, and Reactive Molecular Dynamics is a promising approach to obtain this crucially needed information. The development of a predictive method for condensed-phase reaction kinetics can provide significant insight into polymer ammability, thus helping guide future synthesis of fire-resistant polymers. Through this dissertation, a new reactive forcefield, RMDff, and Reactive Molecular Dynamics program, RxnMD, have been developed and used to simulate such material chemistry. It is necessary to have accurate description of chemical kinetics to describe quantitative chemical kinetics. …
Synthesis And Interfacial Behavior Of Functional Amphiphilic Graft Copolymers Prepared By Ring-Opening Metathesis Polymerization, Kurt E. Breitenkamp
Synthesis And Interfacial Behavior Of Functional Amphiphilic Graft Copolymers Prepared By Ring-Opening Metathesis Polymerization, Kurt E. Breitenkamp
Open Access Dissertations
This thesis describes the synthesis and application of a new series of amphiphilic graft copolymers with a hydrophobic polyolefin backbone and pendent hydrophilic poly(ethylene glycol) (PEG) grafts. These copolymers are synthesized by ruthenium benzylidene-catalyzed ring-opening metathesis polymerization (ROMP) of PEG-functionalized cyclic olefin macromonomers to afford polycyclooctene- graft -PEG (PCOE- g -PEG) copolymers with a number of tunable features, such as PEG graft density and length, crystallinity, and amphiphilicity. Macromonomers of this type were prepared first by coupling chemistry using commercially available PEG monomethyl ether derivatives and a carboxylic acid-functionalized cycloctene. In a second approach, macromonomers possessing a variety of PEG …
The Tensile Properties Of Compatible Glassy Polyblends Based Upon Poly(2,6-Dimethyl-1,4-Phenylene Oxide)., Lothar Walter Kleiner
The Tensile Properties Of Compatible Glassy Polyblends Based Upon Poly(2,6-Dimethyl-1,4-Phenylene Oxide)., Lothar Walter Kleiner
Doctoral Dissertations 1896 - February 2014
The mechanical behavior of compatible glassy polyblends based upon poly (2 , 6-dimethyl-l , 4-phenylene oxide) (PPO) was investigated. In particular, the influence of composition, molecular weight, and molecular weight distribution upon the large deformation tensile properties was assessed. Various possible correlations between the experimentally determined moduli and theory are considered. Included are correlations with density, packing density, composite theory and lattice fluid theory. Similarities in behavior of the compatible glassy polyblends to the phenomenon known as "antiplasticization" is presented. The modeling of the properties of these polymer mixtures via Simplex lattice design is also detailed. Finally, attention is given …