Physical Sciences and Mathematics Commons^™

The Effect Of Illumination On The Conformation And Thermodynamics Of Conjugated Polymers, Brian Frank Morgan

Doctoral Dissertations

This dissertation explores the effects which illumination has on the structure and conformation of conjugated polymers, both in solution and the bulk. Conjugated polymers are an important class of optoelectronic polymeric materials which make up the active layer of key organic electronic devices such as organic photovoltaics, transistors, and light emitting diodes. Considering the strong link between polymer chain structure and device efficiency in these materials, a comprehensive understanding of certain experimental conditions which may influence this conformation and thusly alter the functionality of the devices predicated upon them is of vital importance.

The first part of this dissertation provides …

Synthesis And Behavior Of Stimuli-Responsive Shape-Changing Linear Molecular Bottlebrushes, Daniel Mark Henn

Doctoral Dissertations

Molecular bottlebrushes are composed of polymer side chains densely grafted to a macromolecular backbone. The main focus of this dissertation work is the synthesis and behavior of linear molecular brushes that can undergo unimolecular size and shape changes in response to environmental stimuli in dilute aqueous solution. Chapter 1 provides an introduction to molecular bottlebrushes and stimuli-responsive polymers.

Chapter 2 presents the development of a robust method for the synthesis of well-defined molecular brushes by a “grafting to” approach using copper-catalyzed azide-alkyne cycloaddition “click” reactions. Well-defined, new azide-containing backbone polymers with different lengths and high degrees of azide functionality were …

Functional Hydrophilic Polymers For Solution Assembly And Non-Viral Gene Therapy, Rachel A. Letteri

Doctoral Dissertations

This thesis examines functional hydrophilic polymers designed in linear and comb architectures and that carry functional moieties in the context of solution assembly and non-viral gene therapy. Specifically, polymers containing cations, zwitterions, and reactive groups are investigated as non-viral gene therapy reagents and at oil-water interfaces on droplets. Cations facilitate complexation of nucleic acids and interaction with cellular and nuclear membranes, while zwitterions impart stimuli-responsive solution properties and biocompatibility. Reactive groups, including alkenes, alkynes, and benzylic methylenes, permit post-polymerization modification leading to tunable polymer properties in solution and at interfaces. This work expands the knowledge base related to solution, interfacial, …

Polymer And Small Molecule Designs For Anion Conducting Membranes: Connected Ion-Channel Morphologies And Highly Alkaline Stable Ammonium Cations, Sedef P. Ertem

Doctoral Dissertations

Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE …

Synthesis And Characterization Of New Multifunctional Initiators For Anionic Polymerization And The Use Of Poly(4-Hydroxystyrene) As A Template For New Polymers, Christopher Michael Hurley

Doctoral Dissertations

This dissertation explores the synthesis and use of multifunctional anionic polymerization initiators for the purpose of opening the gateway to the synthesis of polymer architectures of greater complexity. First the multifunctional oxyanion initiator generated by reacting poly(4-hydroxystyrene) with sodium hydride was used to synthesize a previously unknown polymer containing an aryl halide functional group. The homopolymer solution self-assembly behavior of poly(4-hydroxystyrene) and the newly synthesized poly (4-bromo-phenyloxystyrene) were both investigated. This is followed by the synthesis and characterization of multifunctional alkyne core molecules and random copolymers of polystyrene-co-poly(4-hydroxystyrene) which served as templates for the synthesis of new random copolymers of …

Hybrid Micellar Network Hydrogels Of Thermosensitive Hydrophilic Triblock Copolymers And Thermosensitive Hairy Nanoparticles, Bin Hu

Doctoral Dissertations

Hybrid micellar network hydrogels, composed of thermosensitive hydrophilic triblock copolymers and thermosensitive polymer brush-grafted nanoparticles (hairy NPs), exhibit intriguing rheological properties. This dissertation work studies thermosensitive hybrid hydrogels with NPs positioned either inside or outside the core of block copolymer micelles.

Chapter 1 is an introduction. Chapter 2 examines the effect of NP’s location on properties of hybrid hydrogels of a thermosensitive ABA triblock copolymer and hairy NPs. Two batches of thermoresponsive polymer brush-grafted silica NPs and an ABA triblock copolymer with thermosensitive outer blocks were prepared. When the lower critical solution temperature (LCST) of hairy NPs was similar to …

Synthesis And Application Of Polymer Brush-Grafted Nanoparticles As Hydrogel Gelators And Lubricant Additives, Roger Anthony Emory Wright

Doctoral Dissertations

This dissertation describes the synthesis of polymer brush-grafted nanoparticles (hairy NPs) and an analysis of their behavior or utility in multiple areas. The hairy NPs were synthesized from silica NPs functionalized with initiating moieties by surface-initiated atom transfer radical polymerization. A brief introduction to hairy NPs, with a focus on the synthesis and behavior of stimuli-responsive polymer brush-grafted particles, is given in Chapter 1 to provide context for this work.

Chapters 2 and 3 present the synthesis of thermosensitive diblock copolymer brush-grafted nanoparticles designed as hairy NP analogues in place of thermosensitive block copolymers micelles for the construction of hybrid, …

Synthesis And Characterization Of Polymeric Anion Exchange Membranes, Wenxu Zhang

Doctoral Dissertations

As alkaline anion exchange membrane fuel cells (AAEMFC) are regarded as promising and important energy devices, the development of high performance anion exchange membranes are in urgent need, as well as fundamental investigation on the structure-property relationship, which are the motivation of this dissertation. Three different polymer systems are presented and focused on polymer synthesis, material morphology, and ion transport phenomena. Crosslinked membranes are promising as practical materials, however, the understanding and further improvement of its performance is hindered by the lack of an ordered morphology or well-defined chemical structure. In Chapter 2, a series of crosslinked membranes were design …

Nanomaterials At Liquid/Liquid Interfaces: Assembly And Rheology, Tao Feng

Doctoral Dissertations

This dissertation concentrated on the behavior of nanomaterials at liquid/liquid interfaces. A strategy of segregating acid-treated SWCNTs at oil/water interfaces was developed by adding amine-terminated polystyrene (PS-NH₂) in the oil phase. Electrostatic binding between carboxylic acid of SWCNTs and amine drives the assembly of SWCNTs, monitored by pendant drop tensiometry and confocal microscopy. A sharp transition of interfacial segregation against SWCNT solution pH was revealed, with the transition point at the pKa of carboxyl. The reduced SWCNT surface charge density at low pH was found to be beneficial for segregation due to the attenuated repulsions between adsorbed …

Design, Synthesis, And Applications Of Nano-Assemblies Based On Amphiphilic Macromolecules, Hui Wang

Doctoral Dissertations

Recent progress in nanotechnology has been significantly impacting a variety of areas such as utilization in microelectronics, multiphase catalysis, sensing and therapeutics. Our interests are to develop new nanomaterials to understand their structure-property relationships and to utilize them for various applications. In this thesis, we discuss our findings on the design, synthesis and applications of nanomaterials formed by self-assembly of amphiphilic molecules. Micelles are self-assembled nanostructures formed by amphiphilic molecules. They are capable of sequestering hydrophobic guest molecules in an aqueous environment. Other than surfactants, micelles can also be formed by amphiphilic polymers or dendrimers, which are macromolecular surfactants in …

Design Of Romp-Based Protein Mimics For Sirna Delivery, Brittany M. Deronde

Doctoral Dissertations

Designing delivery agents for therapeutics is an ongoing challenge. As treatments and desired cargoes become more complex, the need for improved delivery vehicles becomes critical. Excellent delivery vehicles must ensure the stability of the cargo, maintain the cargo’s solubility, and promote efficient delivery and release. In order to address these issues, many research groups have looked to nature for design inspiration. Proteins, such as HIV-1 TAT and Antennapedia homeodomain protein, are capable of crossing cellular membranes. However, due to the complexities of their structures, they are synthetically challenging to reproduce in the laboratory setting. Being able to incorporate the key …

Stimuli Responsive Polymer Self-Assembly And Disassembly, Jiaming Zhuang

Doctoral Dissertations

Stimuli responsive polymer assemblies have been long investigated for drug application due to their flexibility for surface functionalization to achieve desired interfacial property and capability of acting as a host for payloads encapsulation. These interfacial and host-guest properties are very critical and need to be customized really depending on nature of cargos and specific delivery application. More importantly, these properties are always desired to be adaptable in different environments. For instance, adjustable interfacial property can facilitate the carrier to overcome a variety of different barriers before it reach the target while changeable host-guest property allows to selectively releasing the payload …

Refractive Index Engineering And Optical Properties Enhancement By Polymer Nanocomposites, Cheng Li

Doctoral Dissertations

The major part of this dissertation discusses the engineering of the refractive index of materials using solution-processable polymer nanocomposites and their applications in building optical components and devices. Three particular polymer nanocomposites have been introduced to achieve materials with tunable refractive indices and enhanced optical properties, which can be used to manipulate the behavior of light or electromagnetic radiations. In the first system, polyhedral oligomeric silsesquioxane (POSS)/polymer nanocomposites are developed. Thin films with tunable, low refractive indicies were fabricated from the composites. The mechanical strength of these films was characterized, and their application in antireflective coatings is discussed. In the …

(I) Polymer Nanocomposites: Rheology And Processing For Mesoporous Materials And (Ii) Nanopatterning Of Metal Oxides Using Soft Lithography, Rohit Kothari

Doctoral Dissertations

The research in this dissertation is categorized into two parts. The first part is focused on investigation of order-to-disorder transitions (ODT) in nanocomposites of an amphiphilic block copolymer containing various hydrogen-bonded additives, and fabrication of novel mesoporous silica based materials by utilizing such nanocomposites as templates. Disordered Pluronic®, poly(ethylene oxide) (PEO)−poly(propylene oxide) (PPO)−PEO triblock copolymer upon blending with small molecule additives containing hydrogen-bond-donating functional groups (carboxyl or hydroxyl) result into ordered nanoscale morphologies by preferentially interacting with the hydrophilic PEO chains in the Pluronic®. The dependence of ODT-temperature in these novel Pluronic®/small-molecule-additive complexes on composition, number and type of functional …