Polymer and Organic Materials Commons^™

Improving Ductility Of Slender Reinforced Concrete Shear Walls With Frp Sheets And Splay Anchors, Luke M. Ostrom

Architectural Engineering

The Sylmar earthquake of 1971 caused significant damage to slender, non-ductile reinforced concrete (RC) shear wall buildings in California. A later survey by the Concrete Coalition in 2011, under the guidance of EERI members, indicated that there are over 3000 vulnerable concrete buildings in California [8]. This led to City of Los Angeles (LA) Ordinance 193893 enacted in 2015, which requires mandatory upgrades to these concrete buildings by 2035. Current practice to meet the requirements of this ordinance, with respect to RC wall buildings, involves adding new shear walls to the building plan or increasing the cross-sectional area of existing …

Polyhedral Oligomeric Silsesquioxane-Phosphate Glass Matrix Nanocomposites With Additional Chapter On Phosphate Glass-Poly(Ethylene Terephthalate) Matrix Composites, Kyoungtae Kim

Dissertations

Preparation and characterization of tin fluorophosphate glass (Pglass) matrix nanocomposites incorporating polyhedral oligomeric silsesquioxane (POSS) were investigated on the structural, thermal, morphological, mechanical, and rheological properties. Various processes including synthesis, extrusion and sintering processes were applied to prepare the nanocomposite samples. Another application of POSS with hydrophobic functional groups on the well-structured nanoscale silicate cage with three silanol groups was investigated to present the feasibility to use POSS molecule as a coating material on the surface of the hydrophilic inorganic glass. In addition, Poly(ethylene terephthalate) polymer matrix composites incorporating Pglass was studied to present the benefits of the Pglass with …

Hydrogen Bond Mediated Water Structuring, Diffusion, And Elastic Properties In Acrylamide Copolymer Glycohydrogels, April Levu Fogel

Dissertations

Glycohydrogels have recently gained considerable interest as biocompatible and high water content hydrogels that have similar physicochemical nature to the cell membrane, making them ideal materials for targeted biomedical and personal care applications (e.g., drug delivery systems, biosensors, and contact lenses). Regardless of the specific application, water-polymer and water-water hydrogen bonding interactions have been shown to dictate hydration stability and diffusional properties in traditional hydrogel architectures (e.g., crosslinked HEMA). However, due to the development of glycohydrogel materials within the past two decades, most literature focuses on synthetic techniques and general hydration characteristics. Furthermore, scant literature examines the effect of hydrophobically …

Engineering High Performance Epoxy Thermosets Using Next-Generation Impact Modification, Madhura Pawar

Doctoral Dissertations

Optimization of fracture toughness of high T_g thermosets was done through systematic investigation of different formulations of reactive functional modifiers using soft particle impact modification. Important parameters like particle size, interparticle distance (IPD) were varied by altering cure kinetics and modifying the molecular architecture of the additives. The best performing systems showed an increase in fracture toughness of 70-80% with an optimum R_p of 1.3 μm and IPD of 0.4 μm at 15 vol% impact modifier. In addition, a new platform of using block copolymer blends was studied for its feasibility to achieve non-spherical morphology for effective impact …

Fabrication Of High Refractive Index, Periodic, Composite Nanostructures For Photonic And Sensing Applications, Irene Howell

Doctoral Dissertations

This dissertation examines methods of fabricating high refractive index, periodic structures and their applications. Structures with a refractive index periodicity in one-dimensionally are fabricated by stacking layers of (high-refractive index) nanoparticle-filled and unfilled layers. More complex two- and three-dimensional structures are fabricated by direct printing of nanoparticles via solvent-assisted soft nanoimprint lithography. Polymer-nanoparticle composites are an active area of research and development especially for photonic applications. We show use of two composite formulations, first for fabrication of one-dimensional photonic crystals, and second for scalable UV-nanoimprinting. One dimensional photonic crystals, which possess a periodicity in refractive index, result in a constructive …

A Systematic Investigation Of Condensation Heat Transfer Using Asymmetric Micro-Scale Surfaces, Emily Brown

LSU Master's Theses

Asymmetric surfaces been shown to inducing unidirectional motion in the Leidenfrost regime; however, very minimal research has been conducted to investigate whether these surface can enhance condensation through the same means. The investigation of heat transfer of ratchets in condensation is a relatively untapped area of study, specifically ratchets with superhydrophobic properties. Anticipated difficulty lies in creating surfaces features or coatings that retain the ratchets and can adequately sustain optimal wetting state of Cassie-Baxter required to improve heat transfer performance during condensation. This study serves to investigate whether ratchets are a feasible surface feature to enhance condensation heat transfer. First, …

Swelling Induced Deformation Of Thermally Responsive Hydrogels, Ying Zhou

Doctoral Dissertations

Hydrogels are crosslinked polymeric networks imbibed with aqueous solutions. They undertake dramatic volume changes through swelling and deswelling processes, which can be stimulated by factors like temperature, pH or different chemicals. These unique properties render hydrogels particularly interesting for shape morphing related applications. In this thesis, we focus on the swelling induced deformation of thermally responsive hydrogels with lower critical solution temperatures (LCSTs), including poly(N-isopropylacrylamide) (PNIPAm) and poly(N,N-diethylacrylamide) (PDEAm). Particularly, benzophenone containing monomers are copolymerized with NIPAm or DEAm to create photocrosslinkable temperature-responsive polymers, which allows fabrication of hydrogels with controlled shapes and crosslinking …

Extreme Indentation And Fracture Of Soft Polymer Gels, Shruti Rattan

Doctoral Dissertations

The mechanical properties of conventional hard materials, such as metals and ceramics, have received widespread attention in the past several decades; however mechanical characterization, failure in particular, of soft materials, such as polymer gels, elastomers, and biological tissues and organs, has largely been ignored. While practical issues such as difficulty in handling, processing, and slippage offer complexities in characterization, the breakdown of the fundamental assumptions of linear elastic fracture mechanics due to large strains prior to failure, significant energy dissipation ahead of a crack tip and rate and time dependent effects makes understanding of failure in soft materials even more …

Increasing Organic Semiconductor Performance Through Chemical And Processing Modifications, Edmund Burnett

Doctoral Dissertations

This thesis focuses on tuning molecular packing of organic semiconductors through processing or chemical modifications to increase performance and establish structure-property relationships. Chapter 2 utilizes differing processing techniques to alter the molecular packing of bistetracene in the thin film and thorough polymorph characterization to relate the modification of molecular packing to the increase in charge mobility and mechanism. Chapter 3 introduces the oligomer as a model system to resolve issues that would be difficult or impossible using polymeric systems, due to their monodispersity and increased crystallinity allows for more detailed structural characterization. In this chapter we determine a crystal packing …

Chemically Modified Cellulosic Materials As Multi-Functional Agents In Polymer Composites, Jinlong Zhang

LSU Doctoral Dissertations

Comparative flame retardancy of micro wood fiber plastic composites (WPCs) with fire retardants (1,2-bis(pentabromophenyl) ethane, metal hydroxides and nanoclay) was studied. The fire additives (1,2-bis(pentabromophenyl) ethane as well as magnesium hydroxide) obviously enhanced the fire retarding properties of WPCs. Especially, 1,2-bis(pentabromophenyl) ethane significantly reduced the total heat release as well as heat release rate. In addition, a synergistic effect of 1,2-bis(pentabromophenyl) and nanoclay was achieved for the enhanced fire retarding performance of WPCs.

A copolymer of cellulose nanocrystals (CNCs) and poly(N-vinylcaprolactam) (PVCL) (PVCL-g-CNCs) for use as thermally-responsive polymers with low critical solution temperatures (LCSTs) was synthesized via atom transfer radical …

Chemical Modification Of Lignin Into Advanced Materials, Soheil Hajirahimkhan

Electronic Thesis and Dissertation Repository

Fossil fuel resources are being used today for most of humankind’s energy and chemical/material needs. The inevitable demise of these resources has created significant interest in the field of biomass and particularly, lignin valorization. As the world’s second most abundant polymer, more than 98% of the annually produced lignin is under-utilized either as an on-site heat source, or as landfill. Thus, finding practical approaches to modifying this inexpensive sustainable resource into materials of high value can be the next leap in lessening the dependence on fossil fuel resources and thus, developing a sustainable future.

In this thesis, kraft lignin is …

Microinjection Molding Of Carbon Filled Polymer Composites, Shengtai Zhou

Electronic Thesis and Dissertation Repository

There has been increasing demand for microparts in the areas of electronics, automotive, biomedical and micro-electro-mechanical systems. Microinjection molding (μIM) is becoming an important technology to fabricate miniature products or components to satisfy the ever-increasing needs of the above industries. Polymers and polymeric composites are ubiquitously adopted as molding materials due to their weight advantage, good processability and excellent resistance to corrosion.

Earlier studies have been primarily focused on the μIM of unfilled thermoplastics; however, microparts with multi-functionalities, such as electrical, thermal and mechanical properties are always accommodated by using multi-functional filler loaded polymer composites. Recently, μIM of carbon nanotubes …

New Methods For Understanding And Controlling The Self-Assembly Of Reacting Systems Using Coarse-Grained Molecular Dynamics, Stephen Thomas

Boise State University Theses and Dissertations

This research aims at developing new computational methods to understand the molecular self-assembly of reacting systems whose complex structures depend on the thermodynamics of mixing, reaction kinetics, and diffusion kinetics. The specific reacting system examined in this study is epoxy, cured with linear chain thermoplastic tougheners whose complex microstructure is known from experiments to affect mechanical properties and to be sensitive to processing conditions. Mesoscale simulation techniques have helped to bridge the length and time scales needed to predict the microstructures of cured epoxies, but the prohibitive computational cost of simulating experimentally relevant system sizes has limited their impact. In …

Engineering Next Generation Anisotropic Materials And Composites, Nihal Kanbargi

Doctoral Dissertations

Polymer-based composite systems have been developed for a wide variety of applications ranging from aerospace to electronics. My work has focused on the structure-process-property relationships of anisotropic polymeric materials and composites, aimed primarily for structural applications. Anisotropic materials such as fibers have superior mechanical properties along the axial direction and this property can be exploited to engineer exceptionally strong and light materials. In the first chapter, we discuss the physics of degradation of Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers. PBO, a fiber of extraordinary tensile modulus and strength has been found to degrade rapidly under moderate conditions of humidity and heat. Solid-state NMR …

Microstructural Characterization Of Shear Transformation Zones And Modeling Indentation Size Effect In Amorphous Polymers, Leila Malekmotiei

LSU Doctoral Dissertations

The first aim of this work is developing a procedure for experimental and analytical characterization of nano-scale microstructures which mediate large scale deformation in amorphous polymers. Glassy polymers are extensively used as high impact resistant, low density, and clear materials in industries. Nevertheless, their response under severe loading conditions is yet to be appropriately unraveled. Due to the lack of long-range order in the microstructures of glassy solids, their plastic deformation is different from that in crystalline solids. Shear Transformation Zones (STZs) are believed to be the main plasticity carriers in amorphous solids and defined as the localized atomic or …

Effect Of Material Viscoelasticity On Frequency Tuning Of Dielectric Elastomer Membrane Resonators, Liyang Tian

Electronic Thesis and Dissertation Repository

Dielectric elastomers (DEs) capable of large voltage-induced deformation show promise for applications such as resonators and oscillators. However, the dynamic performance of such vibrational devices is not only strongly affected by the nonlinear electromechanical coupling and material hyperelasticity, but also significantly by the material viscoelasticity. The material viscoelasticity of DEs originates from the highly mobile polymer chains that constitute the polymer networks of the DE. Moreover, due to the multiple viscous polymer subnetworks, DEs possess multiple relaxation processes. Therefore, in order to predict the dynamic performance of DE-based devices, a theoretical model that accounts for the multiple relaxation processes is …

Development Of Low Cost, Environmentally Friendly And High Strength Carbon Foams From Bread And Cake, Laura Mountain-Tuller

Materials Engineering

Carbon foam is a high niche material that consists of a highly porous, three-dimensional cellular network that is characterized by extremely high strength-to-weight ratios and low thermal conductivity. Due to these properties, carbon foams excel in structural and thermal applications, especially in the aerospace industry. Typically, carbon foams are formed through a heating process called pyrolysis of polymer precursors with high carbon content. This process is done at high temperatures in an oxygen free environment. These precursors are expensive to make and use toxic chemicals to produce, therefore, there is a push to find an environmentally friendly and cost-effective method …

Synthesis Of Ɣ-Cyclodextrin Metal Organic Frameworks And The Encapsulation Of Caffeine And Theophylline, Evan Noel Sommerville, Riley Andrew Harden

Materials Engineering

Nanoporous, non-toxic, ɣ-cyclodextrin metal organic frameworks (𝛾-CDMOFs) have potential applications in fields such as drug delivery and organic compound storage. The properties of many methylxanthines (alkaloids such as caffeine and theophylline) could be improved through 𝛾-CDMOF encapsulation, yet little research has been performed on the subject. In this study, 𝛾-CDMOFs were synthesized in order to 1. Determine if the vapor diffusion synthesis method can produce 𝛾-CDMOF crystals that replicate those in literature and 2. Determine if 𝛾-CDMOFs are able to encapsulate methylxanthines. The 𝛾-CDMOFs were synthesized through vapor diffusion of methanol in a solution of ɣ-cyclodextrin and potassium hydroxide (KOH). …

Exploring The Relationship Between Cellular Structure And Mechanical Properties Of Polymer Foams, Timothy Lee Tan

Materials Engineering

Polymer foams are the material of choice for applications that require comfort, cushioning, and high energy absorption. While popular, the relationship between their microstructure and their mechanical properties is not yet strongly predictable. The aim of this project is to look at the different relationships between the area or volume occupied by pores compared to the amount of solid material and determine which method of quantifying this relationship will provide the best prediction of mechanical properties. To examine this relationship, foams of various densities made from either ethylene-co-vinyl acetate or thermoplastic polyurethane were first physically characterized through three methods: (1) …

Preparation And Characterization Of Eva/Cort Microparticles For Rattlesnake Endocrinology Studies, Alexander C. Pauer

Materials Engineering

No abstract provided.

Analysis Of The Low-Cycle Fatigue Behavior Of Silicone Rubber For Biomedical Balloons, Chase Cooper

Materials Engineering

The development of a medical drug delivery device that allows for the deployment drugs into the adventitial tissue of blood vessels requires the inflation of a silicone elastomer. The inflated silicone must be able to consistently endure multiple loading cycles without failing so that the device can operate reliably. There are multiple methods of processing the silicone for the device and the goal of this study is to examine the effect of the various processing methods on the characteristics of the silicone. The Dynamic Mechanical Analysis Machine (DMA) is used to model the conditions of the device’s application by performing …

Voltage-Controlled Deposition Of Nanoparticles For Next Generation Electronic Materials, Subhodip Maulik

LSU Doctoral Dissertations

This work presents both a feasibility study and an investigation into the voltage-controlled spray deposition of different nanoparticles, namely, carbon nanotubes (CNTs), as well as molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) from the transition metal dichalcogenides (TMDCs) family of materials. The study considers five different types of substrates as per their potential application to next-generation device electronics. The substrates selected for this research were: 1) aluminum as a conducting substrate, 2) silicon as a semiconducting substrate, 3) glass, silicon dioxide (SiO₂), and syndiotactic poly methyl methacrylate (syndiotactic PMMA) as insulating substrates.

Since the …

Effects Of Surface-Directed Spinodal Decomposition On Binary Thin-Film Morphology, Michael Brian Wise

Graduate Theses and Dissertations

Preferential wetting can have a significant impact on the kinetics of phase separation in certain systems. The depletion of the wetting component can simply alter domain growth rates or change the structure entirely. In this thesis, we employ a Cahn-Hilliard model to study the evolution of binary thin-films with symmetric surface wetting. Three possible morphologies were identified: discrete, bicontinuous, and a novel quasi-2D bicontinuous structure in which both phases retain continuity throughout the volume as well as on the center xy plane. Using a continuity factor, regions of film thickness versus blend composition were classified as producing a certain morphology. …

Mesoscale Computational Studies Of Thin-Film Bijels, Joseph M. Carmack

Graduate Theses and Dissertations

Bijels are a relatively new class of soft materials that have many potential applications in the technology areas of energy, medicine, and environmental sustainability. They are formed by the arrest of binary liquid spinodal decomposition by a dispersion of solid colloidal nanoparticles. This dissertation presents an in-depth simulation study of Bijels constrained to thin-film geometries and in the presence of electric fields. We validate the computational model by comparing simulation results with previous computational modeling and experimental research. In the absence of suspended particles, we demonstrate that the model accurately captures the rich kinetics associated with diffusion-based surface-directed spinodal decomposition. …

Structure And Property Of Polymers And Biopolymers From Molecular Dynamic Simulations, Xiaoquan Sun

Graduate Theses and Dissertations

Natural and synthetic polymers and biopolymers have been studied for a variety of applications in food emulsion, biopharmaceutical purification, tissue engineering, and biosensor. The structure and property of polymers and biopolymers are critically important to determine their functions. Molecular dynamics (MD) simulations have a unique advantage to explore the structure and property of polymers and biopolymers from the molecular level. In the dissertation, MD simulations were conducted to study the mechanisms of various biological and chemical processes controlled by polymers and biopolymers based on real-world experimental results.

Seven heptapeptides have been screened from a peptide library in our earlier study …

Phase Transitions In Monochalcogenide Monolayers, Mehrshad Mehboudi

Graduate Theses and Dissertations

Since discovery of graphene in 2004 as a truly one-atom-thick material with extraordinary mechanical and electronic properties, researchers successfully predicted and synthesized many other two-dimensional materials such as transition metal dichalcogenides (TMDCs) and monochalcogenide monolayers (MMs). Graphene has a non-degenerate structural ground state that is key to its stability at room temperature. However, group IV monochalcogenides such as monolayers of SnSe, and GeSe have a fourfold degenerate ground state. This degeneracy in ground state can lead to structural instability, disorder, and phase transition in finite temperature. The energy that is required to overcome from one degenerate ground state to another …

Self-Assembled Barium Titanate Nanoscale Films By Molecular Beam Epitaxy, Timothy Allen Morgan

Graduate Theses and Dissertations

One challenge of investigating ferroelectrics at the nanoscale has been controlling the stoichiometry during growth. Historically, the growth of barium titanate (BaTiO3) by molecular beam epitaxy has relied on a growth technique called shuttered RHEED. Shuttered RHEED controls the stoichiometry of barium titanate through the precise deposition of alternating layers of BaO and TiO2. While this approach has achieved 1% control of stoichiometry, finding self-limiting mechanisms to lock-in stoichiometry has been the focus of the growth community. The Goldschmidt tolerance factor predicts an unstable perovskite when barium sits in the titanium lattice site. The BaO-TiO2 phase diagram predicts a low-solubility …

Phase Field Model Of Thermally Induced Phase Separation (Tips) For The Formation Of Porous Polymer Membranes, Ashley Green, Aria Green

Mechanical Engineering Undergraduate Honors Theses

Most membrane research and development has been done through experimental work, which can be costly and time consuming. An accurate computational model would greatly reduce the need for these experiments. The focus of the research presented in this paper is to create an accurate computational model for membrane formation using thermally induced phase separation (TIPS). A phase field model is employed to create this model including the Cahn Hilliard Equation and Flory Huggins Theory. This model produced computational results that correspond well with theoretical and experimental results. The model was then adapted to correspond to the PVDF/DPC polymer-solvent system by …

Corner Sealants For Tactical Shelters, Janine Carlita Nowak

Honors Theses

The demand for a lightweight, easy-assembly tactical shelter is high for those faced with unexpected disasters and global conflicts. This project focuses on designing and prototyping the corner sealant for such a shelter. Two materials were chosen and tested: an in-house thermoplastic polyurethane (TPU) and Texin 950. Thermogravimetric Analysis (TGA) was performed on both of these materials. The in-house TPU showed initial degradation at 282.50 °C and sample degradation at 457.45 °C. Similarly, Texin 950 showed initial degradation at 293.68 °C and sample degradation at 453.26 °C. Differential Scanning Calorimetry (DSC) was then run. The crystallization temperature (Tc) was observed …

Characterization And Selection Of Hydroxyl-Terminated Polybutadiene Polymers For High-Strain Applications, Nathaniel Prine

Honors Theses

Understanding the behavior of hydroxyl-terminated polybutadiene (HTPB) as a composite matrix is imperative for the development of future military and aerospace munition technology. As a vital component of solid rocket fuel, HTPB strongly contributes to the fatigue behavior, burn-rate, and other properties that can cause critical failure of the rocket if not formulated properly. The purpose of this research is to identify traits characteristic of poor-performing HTPB matrices by analyzing two samples labeled as either “good” or “bad” based on their performance as a fuel matrix. Samples were analyzed via 1H NMR and GPC to determine their epoxy content, hydroxyl …