Polymer Chemistry Commons^™

Surface And Interfacial Design And Control Of High Performing Thermoplastics: Polysulfones And Beyond, Katrina Marie Knauer

Dissertations

The study of a class of materials almost always begins with the development of an understanding of properties in the bulk state. However, it is the study of surface critical phenomena that has led to a number of new important insights into polymer behavior. A systematic understanding of physical properties in the immediate vicinity of surface and interfacial layers, which cannot be deduced by simple extrapolation of bulk properties, is of significant importance for advancements in polymer applications where the interface drives performance, such as in membranes, coatings, drug-delivery systems, medical devices, and composites.

First, the surface and interfacial modification …

Energy Management Mechanisms Employed At The Human-Material Interface Of Traditional And Minimalist Shod Running, Nadine M. Lippa

Dissertations

From recreational to elite athletes, greater than 50% of runners sustain overuse injuries each year, prompting substantial research efforts to identify causes of—and solutions to—the high injury rate. Different shoe types and material property degradation have been related to injury. Two popular footwear types are traditional shoes with thick graded soles and minimalist running footwear with thinner foam and/or non-graded soles. Notwithstanding 45 years of significant modifications to shoe design features, gained knowledge in kinesiology, and advanced technologies in polymer science, runner injury rates have not decreased and EVA foam has remained the primary running shoe midsole material since the …

Curing Of Polymer Thermosets Via Click Reactions, Mark Richard Brei

Dissertations

In the first project, an azide functional resin and tetra propargyl aromatic diamines were fabricated for use as a composite matrix. These systems take already established epoxy/amine matrices and functionalize them with click moieties. This allows lower temperatures to be used in the production of a thermoset part. These new systems yield many better mechanical properties than their epoxy/amine derivatives, but their T_gs are low in comparison.

The second project investigates the characterization of a linear system based off of the above azide functional resin and a difunctional alkyne. Through selectively choosing catalyst the linear system can show …

Addressing The Issues Of Drug Delivery Via Advanced Macromolecular Design, Brooks Allen Abel

Dissertations

The work described in this dissertation focuses on the development of synthetic approaches toward novel polymer architectures that specifically address the issues of in vivo drug delivery. Successful implementation of the synthetic methodologies described herein required fundamental investigations into the underlying chemistries in ways that now provide greater insights into the nature of the these chemical reactions.

In Section I, the synthesis of tunable pH- and CO₂-responsive sulfonamide-containing polymers using reversible addition-fragmentation chain transfer (RAFT) polymerization is described. Initially, poor polymerization control of methacryloyl sulfonamide (MSA) monomers was observed using traditional RAFT polymerization conditions. Ultimately, reducing the polymerization …

Hybrid Aryl-Ether-Ketone And Hyperbranched Epoxy Networks, John Misasi

Dissertations

In this dissertation, relationships between chemical structures, cure kinetics and network architectures are correlated to bulk mechanical properties for novel, hybrid epoxy-amine networks. The work is split into two primary sections: the first is the synthesis and characterization of multifunctional glassy networks based on aryl-ether-ketone diamine curatives, while the second is based on the synthesis and characterization of hyperbranched epoxy polymers and their resulting networks.

Three aryl-ether-ketone (AEK) diamines of increasing molecular weights were synthesized and used to cure 4,4’-tetraglycidylether of diaminodiphenylmethane (TGDDM); the resulting networks were compared to 4,4’-diaminodiphenyl sulfone cured TGDDM. Architectural differences were created by varying cure …

Development Of Dual-Cure Hybrid Polybenzoxazine Thermosets, Jananee Narayanan Sivakami

Dissertations

Polybenzoxazines are potential high performance thermoset replacements for traditional phenolic resins that can undergo an autocatalytic, thermally initiated ring - opening polymerization, and possess superior processing advantages including excellent shelf-life stability, zero volatile loss and limited volumetric shrinkage. The simplistic monomer synthesis and availability of a wide variety of inexpensive starting materials allows enormous molecular design flexibility for accessing a wide range of tailorable material properties for targeted applications. Despite the fact, once fully cured, benzoxazines are difficult to handle due to their inherent brittleness, leaving a very little scope for any modifications. The motivation of this dissertation is directed …

Hydrogen Bond-Mediated Structural Order In Hydroxylated Bis-Mpa Dendritic Polymers: Experimental And Molecular Dynamics Simulation Study, Maliha N. Syed

Dissertations

Dendritic architectures are echoed throughout nature. While the significance of these pervasive patterns is not entirely clear, connections between their structures and physical properties are fascinating to contemplate. Particular interest has been paid to a family of synthetically manufactured and commercially available dendritic polymers based on 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) as a monomer. Composed of two hydroxyls and a carboxyl group, bis-MPA based structures hydrogen bond (H-bond) profusely. Given the high concentration and unique spatial orientation of end-groups, as well as the multitude of carbonyl, ester, and ether interior H-bond acceptors, a set of distinct H-bond organizations may be observed …

Mechanochemical Investigation Of A Glassy Epoxy-Amine Thermoset Subjected To Fatigue, Stephen Finley Foster

Dissertations

Covalent bonds in organic molecules can be produced, altered, and broken through various sources of energy and processes. These include photochemical, thermochemical, chemical, and mechanochemical processes. Polymeric materials derive their physical properties from the time scale of motion, summation of intermolecular forces, and number of chain entanglements and crosslinks. Glassy thermoset polymers experience mechanical fatigue during dynamic stress loading and properties diminish with inevitable material failure at stress levels below the ultimate tensile strength (UTS). Damage modeling has been successful in predicting the number of cycles required to induce failure in a specimen due to stress. However, it does not …

Aqueous Raft Polymerization Of Glycopolymers For Peptide Interaction Studies And Antimicrobial Peptide Mimics For Antimicrobial Activity And Selectivity Studies, Sarah Elizabeth Exley

Dissertations

The first section of this work describes the synthesis and characterization of novel glycopolymers synthesized to model GM1 gangliosides, a glycolipid found in neuronal cells. Glucose and galactose were attached to N-hydroxyethyl acrylamide, using chemistry that granted control over the stereochemistry at the C1’ carbon of each saccharide, and polymerized via aqueous RAFT (aRAFT). Homopolymers, targeting either 30 or 300 DP, and copolymers, with N-dimethyl acrylamide, were prepared as a glycopolymer platform for investigation of amyloid β (Aβ), a naturally occurring peptide associated with Alzheimer’s disease, aggregation. Aβ aggregation kinetics and aggregate size in the presence of glycopolymer were determined. …

Continuous Polymer Reactor Design, David Sujay Kingsley

Dissertations

Twin screw extruders can be used as continuous polymer reactors to process polymers, which are conventionally made through batch reactors. Batch processes have certain undesirable qualities such as improper mixing and the inability to precisely control the reaction, which leads to variation between batches and potential exotherms. The work presented in this dissertation investigates the use of continuous polymer reactor designs to efficiently process renewable sourced thermoplastic polyurethanes (TPU), and prepreg epoxy matrix prepolymers.

The overall goal of this research is to highlight the modularity of twin screw extruders as continuous polymer reactors to synthesize the relevant polymers. Chapter I …

Utilization Of Aqueous Raft Prepared Copolymers To Improve Anticancer Drug Efficacy, Andrew Christopher Holley

Dissertations

The advent of controlled radical polymerization (CRP) techniques, along with advancements in facile conjugation chemistry, now allow synthetic tailoring of precise, polymeric architectures necessary for drug/gene delivery. Reversible addition- fragmentation chain transfer (RAFT) polymerization and its aqueous counterpart (aRAFT) afford quantitative control over key synthetic parameters including block length, microstructure, and placement of structo-pendent and structo-terminal functionality for conjugation of active agents and targeting moieties. The relevance of water-soluble and amphiphilic (co)polymers synthesized by RAFT for in vitro delivery of therapeutics in biological fluids is an especially attractive feature. In many cases, polymerization, binding, conjugation, …

Tuning Responsiveness Of Polypeptide Based Block Copolymers For Drug Delivery, Ashley J. Johnson

Dissertations

The goal of this dissertation was to tune the pH response and self-assembled morphologies of amphiphilic polypeptide block copolymers for use as drug delivery vehicles. Poly(L-lysine) and poly(L-glutamtic acid) are responsive, ionizable polypeptides that undergo secondary structure transitions, from α-helix to random coil, whereby the change in conformation of the peptide chain results in changes to the global morphology of a self-assembled system. The main focus of this work was to understand how changes in the polymer composition and the local environment can lead to control over the behavior of the overall system. First, the responsive behavior of poly(L-lysine) block …

Investigation Of Glassy State Molecular Motions In Thermoset Polymers, Jianwei Tu

Dissertations

This dissertation presents the investigation of the glassy state molecular motions in isomeric thermoset epoxies by means of solid-state deuterium (²H) NMR spectroscopy technique. The network structure of crosslinked epoxies was altered through monomer isomerism; specifically, diglycidyl ether of bisphenol A (DGEBA) was cured with isomeric amine curatives, i.e., the meta-substituted diaminodiphenylsulfone (33DDS) and para-substituted diaminodiphenylsulfone (44DDS). The use of structural isomerism provided a path way for altering macroscopic material properties while maintaining identical chemical composition within the crosslinked networks.

The effects of structural isomerism on the glassy state molecular motions were studied using solid-state ²H …

Computational And Experimental Investigation Into Yield Behavior And Cure Rate Dependence Of Thermoset Polymers, Christopher Harold Childers

Dissertations

This dissertation is broken down into two primary sections: firstly, the development and improvement of molecular dynamics simulations of thermoset matrix polymers including their use in understanding molecular response to applied strain deformation and secondly, the discernment of a cure heating ramp rate dependence of the final molecular and macro-molecular properties of thermoset matrix polymer.

The molecular dynamics section will discuss the development of molecular dynamics simulations of thermoset epoxy/amine matrix polymers, and the implementation of this work to determine the underlying molecular level events that cause thermoset matrix polymer yield. It will report a novel method for the determination …

Design And Synthesis Of Flexible And Functional Polybenzoxazine Thin Films, Austin David Baranek

Dissertations

Polybenzoxazines offer the unique ability to incorporate a variety of properties and functionality into a single polymer network through simple synthetic techniques. However, within benzoxazine materials exist certain drawbacks of which brittleness is the primary issue when exploring thin film applications. This brittleness leads to poor mechanical stability and would reduce the lifetime of any device sought after. It is, however, through the simplistic nature of the benzoxazine monomer synthesis that the mechanical stability could be addressed chemically, avoiding the complications of using rubber toughening agents or plasticizers. The monomer synthesis offers tailorability of both the phenol and amine to …

In Situ Quenching And Post-Polymerization Modification Of Telechelic Polyisobutylene, Todd Raymond Hartlage

Dissertations

Polyisobutylene (PIB) is a saturated hydrocarbon elastomer that can only be produced by cationic polymerization. The water-initiated, chain transfer controlled synthesis conducted on an industrial scale produces monofunctional PIB with mixed olefin end groups. Living cationic techniques produce mono- and di-functional telechelic PIB. In situ quenching is the process of adding functional molecules to the polymerization reactor after all monomer is consumed. These quencher species bond to the chain ends, installing their latent functionality onto the polymer chain. To date, all quenchers utilized have been soft π-nucleophiles.

In the first project, free thiols, both aromatic and aliphatic, are shown to …

Relation Between The Adsorption Behavior And Bulk Complexation In Oppositely Charged Polyelectrolyte-Surfactant Systems: Effect Of Polyelectrolyte Concentration, Molecular Weight, Charge Localization And Backbone Rigidity/Hydrophobicity, Vipul Suhas Padman

Dissertations

Due to a wide range of applications, much emphasis has been placed on understanding the physicochemical behavior of polyelectrolyte/surfactant complexes, both at air-water interface and in the bulk. However, the correlation between the adsorption behavior and complexation in the bulk is less explored. In this research, this correlation is investigated and its dependence on polyelectrolyte concentration, molecular weight, charge localization and backbone rigidity and hydrophobicity is studied. The polyelectrolyte concentration is normalized with respect to it critical overlap concentration in order to compare the polymer in same concentration regime. Different polyelectrolyte systems were used to analyze the polyelectrolyte structural effect: …

Synthesis And Characterization Of Polyisobutylene-Block-Polyamides As Novel Thermoplastic Elastomers, Lauren Renee Kucera

Dissertations

Academic research has focused on two main areas of the living carbocationic polymerization (LCP) of isobutylene (IB): (1) the in-depth study and understanding of mechanistic features of the polymerization, and (2) the utilization and manipulation of the unique aspects of PIB in order to produce practically useful polymeric materials. The research included in this dissertation focuses mainly on the latter objective. This work details three main areas of research: (1) the copolymerization of PIB and polyamides (PA) to form novel thermoplastic elastsomers (TPEs), (2) the mechanical, physical and thermal properties of the novel PIB-PA materials, and (3) the use of …

Photopolymerization And Characterization Of Modified Thiol-Ene Networks, Bradley James Sparks

Dissertations

Photopolymerization provides a unique ability to control variables typically uncontrollable using traditional thermally initiated polymerization, thus leading to its use in a broad range of commercial operations. Many of the traditional photopolymers suffer from several setbacks, including oxygen inhibition, unwanted stress buildup which leads to bulk shrinkage, etc., which ultimately lead to diminished polymer performance. The photopolymerization of multifunctional thiols and alkenes has been shown to provide a means to improve upon the weaknesses of traditional photoinitiated polymerizations. The free radical polymerization of thiol and –ene monomers occurs via a series of free radical chain transfer events, as a result, …

Dynamic Bioactive Stimuli-Responsive Polymeric Surfaces, Heather Marie Pearson

Dissertations

This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of –COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface …

Biological And Biologically Inspired Polymers For Interface Modification, Lea Clayton Paslay

Dissertations

Naturally occurring macromolecules are produced for a specific function and have the selectivity to accomplish objectives with little waste in energy. The scientific community strives to develop smart, efficient molecules on an economical scale, thus lessons can be learned from nature and applied to cost effective synthetic systems. First, the mimicry of naturally occurring antimicrobial peptides (AMPs) will be described. AMPs show great potential as alternatives to conventional antibiotics as they can selectively bind and eliminate pathogenic bacteria without harming eukaryotic tissues. Aqueous reversible addition–fragmentation chain transfer (RAFT) polymerization was utilized to prepare primary and tertiary amine containing AMP polymer …

Investigations Toward Tunability Of Mechanical, Thermal, And Impact Properties Of Thiol-Ene Networks For Novel High Energy Absorbing Materials, Olivia Devon Mcnair

Dissertations

The UV polymerization of thiols with electron rich alkenes is a highly resourceful reaction that has been utilized by scientists within various disciplines to produce an even more versatile display of applications. This dissertation focuses on a newer application, thiol-ene network (TEN) materials for energy absorption devices. TEN networks display a host of positive polymer properties such as low stress, high optical clarity and uniformity, but they also suffer from unfavorable mechanical properties such as low toughness and elongation at break. The poor mechanical properties demonstrated by TENs prohibit them as choice materials for applications requiring thicker material forms, including …

Synthesis Of Polyhedral Oligomeric Silsesquioxane (Poss) Functionalized Carbon Nanotubes For Improved Dispersion In Polyurethane Films, Xiaonan Kou

Dissertations

Carbon nanotube (CNT) polymer nanocomposites are promising advanced materials. These materials exhibit the advantages of traditional polymeric materials, such as being light weight and easy to process, combined with the potential to exhibit enhanced mechanical, thermal and electrical properties compared to pure polymers. To achieve substantial improvement of composite properties at low CNT loading, uniform dispersion of CNTs in the polymer matrix and strong CNT-polymer interfacial interaction are needed. However, it is difficult to achieve adequate dispersion and interfacial interactions due to the inert nature of CNTs. In this project, polyhedral oligomeric silsequioxane (POSS) will be used as a dispersing …

Nanoparticle Filled Polymeric Systems For Gas Barrier And Flame Retardant Properties, Yingji Wu

Dissertations

Polymer composite gas barrier and fire retardant properties were studied in this investigation. An increase in the gas barrier property was observed by adding silicate nanotubes or clay nanoparticles into polymeric systems. Oxygen permeability, diffusivity, solubility and water vapor permeability were determined for polyimide/silicate nanocomposites with 0 to 9.99% (vol/vol) filler loading. Both oxygen and water vapor permeability for the system gradually decreased when adding increasing amounts of nanofiller up to 4.50% (vol/vol) and increase again after that. The permeability decrease was caused by both the diffusivity and solubility coefficient changes, although diffusivity (the tortuous factor) is the main reason …

Relationships Between Cure Kinetics, Network Architecture, And Fluid Sensitivity In Glassy Epoxies, Katherine Lea Frank

Dissertations

Relationships between chemical structure, cure kinetics, network morphology and free volume have been correlated with fluid ingress for glassy epoxy network blends. Polymers synthesized from diglycidyl ether of bisphenol-A (DGEBA) and diglycidyl ether of bisphenol-F (DGEBF) were blended with varying amounts of triglycidyl-m-aminophenol (TGAP), tetraglycidyl-4,4-diaminodiphenylmethane (TGMP), napthylamine (NA), adamantylamine (AA), and aminopropylisobutyl polyhedral oliogmericsilsesquioxane (AI-POSS) and cured with 3,3’- and 4,4’- diaminodiphenylsulfone (DDS) to control fractional free volume, average hole size and morphology.

Varying curing profiles introduced morphological changes resulting in differences in network architectures. Epoxy with 10% NA had a smaller V_h (71 ų) …

Utilizing Polymer Topology In Peptide-Based Block Copolymers: Unique Aqueous Assembly And Responsive Behavior, Jacob Griffin Ray

Dissertations

This document details work in the area of amphiphilic polypeptide-based block copolymers that are able to self-assemble into well-defined nanostructures in aqueous solution. The main focus of this work is to understand the impacts of polymer topology on self-assembly behavior and response to external stimulus, particularly pH. Poly(L-lysine) and poly(L-glutamic acid) are two pH-responsive, hydrophilic polypeptides that possess the unique property of undergoing α-helix to random coil secondary structure transitions with pH, and this responsiveness can lead to global morphology changes such as changes in aggregate size or even morphology transitions. These polypeptides are synthesized via ring opening polymerization of …

Understanding Corrosion Protection And Failure Through Model Polymers In Thin Films, Joshua Smith Hanna

Dissertations

When developing a model polymeric system to facilitate in the detection of molecular and microscopic events that preface macroscopic corrosive failure; a better understanding of how polymers can indicate corrosion was accomplished. Initially, the thought that molecular chain scission as a necessity for corrosion to occur had to be tested. Through the utilization of high molecular weight thermoplastic (HMWTP) model polymers, it was found that corrosion protection did not correlate to the quantity of weak bonds within an epoxy-amine polymer matrix. Therefore more sensitive methods of detecting corrosion had to be developed since changes within the polymer matrix did not …

Polymer Surface Engineering Via Thiol-Mediated Reactions, Ryan Matthew Hensarling

Dissertations

Synthesis of polymer brushes to decorate a surface with desired functionality typically involves surface-initiated polymerization (SIP) of functional, but non-reactive monomers. This approach suffers major drawbacks associated with synthesizing sufficiently thick polymer brushes containing surface-attached polymer chains of high molecular weight at high grafting density (i.e. cost, synthetic effort and functional group intolerance during polymerization). The research herein seeks to circumvent these limitations by the decoration of surfaces with polymer chains bearing specific pendent functional groups amenable to post-polymerization modification (PPM). In particular, this dissertation leverages PPM via a specific class of click reactions – thiol-click – that 1) enables …

New Dual Initiators For Polyisobutylene-Based Block And Star Polymers, Yaling Zhu

Dissertations

Polyisobutylene (PIB), available solely by living carbocationic polymerization (LCP), is a commercially important polymer with excellent thermal stability, good flexibility and extraordinary impermeability to gases. Due to these attractive properties, coupling PIB to other polymer blocks is expected to result in new and useful products. Two types of new dual initiators possessing initiating sites for both LCP and atom transfer radical polymerization (ATRP), have been designed for the preparation of AB linear and A2B miktoarm star copolymers, where A is PIB-based block copolymer that grows cationically and B is polyacrylate or other radically-derived polymer block, without intermediate modification.

Mono-cationic mono-radical …

Modern Approaches For Multifunctional Hydrolyzying Thiol-Ene Networks, Nicole Marie Mackey

Dissertations

Marine fouling has been an expensive and time-consuming process for navies and fishermen by the accumulation of marine algae and animals on artificial surfaces. Many coatings have been proposed to combat marine fouling in efforts to extend the lifetime of objects immersed in sea water. However, all coatings tested have either failed to resist fouling for a significant length of time or have released toxins into the environment. We have investigated an environmentally friendly approach to address the problem of marine fouling through the synthesis and preparation of a biocidal and a self-polishing coating. Both novel monomers were prepared containing …