Materials Science and Engineering Commons^™

Synthesis And Characterization Of Poly(Simvastatin) - Incorporated Copolymers And Blends For Bone Regeneration, Theodora Asafo-Adjei

Theses and Dissertations--Biomedical Engineering

Common biodegradable polyesters such as poly(lactic acid) (PLA), poly(lactic-co-glycolic acid) (PLGA) and poly(ε-caprolactone) (PCL) are used as drug delivery vehicles for tissue regenerative applications. However, they are typically bioinert, with drug loading limitations. Polymerizing the active agent or precursor into its respective biodegradable polymer would control drug loading via molar ratios of drug to initiator used for synthesis. Simvastatin was chosen due to its favorable anti-inflammatory, angiogenic, and osteogenic properties. In addition, its lactone ring lends itself to ring-opening polymerization and, consequently, the synthesis of poly(simvastatin) with controlled simvastatin release.

Simvastatin was first polymerized with a 5kDa methyl-terminated poly(ethylene glycol) …

Tunable Nanocomposite Membranes For Water Remediation And Separations, Sebastián Hernández Sierra

Theses and Dissertations--Chemical and Materials Engineering

Nano-structured material fabrication using functionalized membranes with polyelectrolytes is a promising research field for water pollution, catalytic and mining applications. These responsive polymers react to external stimuli like temperature, pH, radiation, ionic strength or chemical composition. Such nanomaterials provide novel hybrid properties and can also be self-supported in addition to the membranes.

Polyelectrolytes (as hydrogels) have pH responsiveness. The hydrogel moieties gain or lose protons based on the pH, displaying swelling properties. These responsive materials can be exploited to synthesize metal nanoparticles in situ using their functional groups, or to immobilize other polyelectrolytes and biomolecules. Due to their properties, these …

Effect Of Interlayers On Mechanical Properties And Interfacial Stress Transfer Of 2d Layered Graphene-Polymer Nanocompsites, Colton C. Roach

Theses and Dissertations--Mechanical and Aerospace Engineering

Graphene, a monolayer of sp²-hybridized carbon atoms arranged in a two-dimensional (2D) lattice, is one of the most important 2D nanomaterials and has attracted tremendous attentions due to its unique geometric characteristics and exceptional mechanical properties. One of the most promising applications of this 2D nanomaterial is in polymer nanocomposites, in which the ultra-stiff, ultra-thin graphene layers function as reinforcement fillers. However, two significant questions remain to be answered: (1) whether the mechanical behaviors of 2D graphene reinforced nanocomposites can be analyzed by the convention composite theory, which is developed primarily for one-dimensional (1D) fiber-type of fillers, and …

The Limits & Effects Of Draw On Properties And Morphology Of Pan-Based Precursor And The Resultant Carbon Fibers, Sarah Edrington

Theses and Dissertations--Mechanical and Aerospace Engineering

The process, structure, and property relationship of PAN fiber as a precursor to carbon fiber was studied. The limitations of stable spinning and property improvement associated with hot draw in solution spinning were found and quantified. Conditions were varied to generated precursor fiber up to the limit of draw, from which actual samples were collected for thermal conversion to carbon fiber. Samples of PAN and subsequent carbon fiber were characterized using tensile testing and x-ray analysis. The effects of draw on modulus and break stress, as well as the orientation of the crystalline structure of both parent precursor and resultant …

Molecular Modeling Of Aerospace Polymer Matrices Including Carbon Nanotube-Enhanced Epoxy, Matthew Radue

Dissertations, Master's Theses and Master's Reports

Carbon fiber (CF) composites are increasingly replacing metals used in major structural parts of aircraft, spacecraft, and automobiles. The current limitations of carbon fiber composites are addressed through computational material design by modeling the salient aerospace matrix materials. Molecular Dynamics (MD) models of epoxies with and without carbon nanotube (CNT) reinforcement and models of pure bismaleimides (BMIs) were developed to elucidate structure-property relationships for improved selection and tailoring of matrices.

The influence of monomer functionality on the mechanical properties of epoxies is studied using the Reax Force Field (ReaxFF). From deformation simulations, the Young’s modulus, yield point, and Poisson’s ratio …

Multiscale Modeling: Thermal Conductivity Of Graphene/Cycloaliphatic Epoxy Composites, Sorayot Chinkanjanarot

Dissertations, Master's Theses and Master's Reports

The thermal property of epoxy as the binder in the Carbon Fiber (CF) composites, especially thermal conductivity is important to achieve the advance technology and to improve the performance of materials. Multiscale modeling including molecular dynamic (MD) modeling and micromechanical modeling is used to study the properties of neat Cycloaliphatic Epoxies (CE) and Graphene nanoplatelet (GNP)/CE with and without covalent functionalization.

The thermal properties (glass-transition temperature, thermal expansion coefficient, and thermal conductivity) and mechanical properties of CE system are investigated by MD modeling using OPLS-All Atom force field. A unique crosslinking technique is developed to achieve the cured CE models …

Formulation And Testing Of Biodegradable Polymeric Coating On Zinc Wires In Cardiovascular Stent Application, Avishan Arab Shomali

Dissertations, Master's Theses and Master's Reports

Biodegradable and biocompatible poly (L-lactic-acid) (PLLA) coating was applied on a modified zinc (Zn) substrate by dip coating, with the intent to delay the bio-corrosion and slow the degradation rate of zinc substrate. 3-(Trimethoxysilyl) propyl methacrylate (MPS) was used for modification of the zinc substrate for promoting the adhesion between the metallic substrate and the polymer coating. It is hypothesized that the delay in Zn biodegradation could be useful in the first several weeks to prevent the early loss of mechanical integrity of the endovascular stent and to improve the healing process of the diseased vascular site. The PLLA coating …

Rubber Additives To Concrete Specimens, Kendall J. Sweitzer, Mary Mccannon

Williams Honors College, Honors Research Projects

Rubber, as an additive to concrete, would hypothetically cause a concrete specimen to take on some mechanical characteristics of the rubber to a certain degree. In particular, the concrete’s durability should increase when exposed to fluctuating temperature conditions due to the rubber additive. This experiment sets out to test crumb rubber as a concrete additive, cured under various atmospheric conditions. The effects shall be measured via a simple concrete compression test.

Unfortunately, several errors took place during experimental process that led to inconclusive results. However, it can be reasonably considered from testing Matrix One that the addition of crumb rubber …

Design Of Natural Rubber Extraction From Tks Dandelion, Jehad S. Alrawajfeh, Trevor Cody, Jason Pogozelski

Williams Honors College, Honors Research Projects

A design was developed for a controlled environment agriculture 3D greenhouse to grow and harvest TKS dandelions, as well as a processing plant to extract natural rubber and inulin from the roots. The design capacity was scaled for both pilot- and full-scale production: 100 and 100,000 tonnes of natural rubber per year, respectively. The byproducts of the process were dandelion greens, inulin, cellulose, and glucose; all of these except for cellulose were able to be valorized. The greenhouse was designed based on existing 3D hydroponic growing environments, and the extraction process was designed based on the original TKS dandelion extraction …

Fabrication Of Flexible, Biofunctional Architectures From Silk Proteins, Ramendra K. Pal

Theses and Dissertations

Advances in the biomedical field require functional materials and processes that can lead to devices that are biocompatible, and biodegradable while maintaining high performance and mechanical conformability. In this context, a current shift in focus is towards natural polymers as not only the structural but also functional components of such devices. This poses material-specific functionalization and fabrication related questions in the design and fabrication of such systems. Silk protein biopolymers from the silkworm show tremendous promise in this regard due to intrinsic properties: mechanical performance, optical transparency, biocompatibility, biodegradability, processability, and the ability to entrap and stabilize biomolecules. The unique …

Tightening The Loop On The Circular Economy: Distributed Plastic Recycling With An Open Source Recyclebot, Shan Zhong

Dissertations, Master's Theses and Master's Reports

Following the goals of a circular economy, the growth of both plastic consumption and prosumer 3-D printing are driving an interest in producing 3-D printer filament from waste plastic. However, traditional recycling can have a significant environmental impact as it demands the collection and transportation of relatively low-density waste plastics to collection centers and reclamation facilities for separation and reconstruction. Compared to the traditional recycling, distributed recycling (where consumers directly recycle their own waste) has the potential to reduce energy consumption because it can save the energy for transportation needed in conventional recycling. A promising method of such distributed plastic …

Functionalization Of Silver Nanoparticles On Membranes And Its Influence On Biofouling, Conor G. Sprick

Theses and Dissertations--Chemical and Materials Engineering

Ultrafiltration (UF) processes are often used as pretreatment before more retentive/costly processes, such as nanofiltration and reverse osmosis. This study shows the results of low-biofouling nanocomposite membranes, loaded with casein-coated silver nanoparticles (casein-Ag-NPs). Membranes were cast and imbedded with Ag-NPs using two approaches, physical blending of Ag-NPs in the dope solution (^PAg-NP/CA membranes) and chemical attachment of Ag-NPs to cast membranes (^CAg-NP/CA membranes), to determine their biofouling control properties. The functionalization of Ag-NPs onto the CA membranes was achieved via attachment with functionalized thiol groups with the use of glycidyl methacrylate (GMA) and cysteamine chemistries. The …

Engineering Icephobic Coatings: Surface Characterization Of Pt Cured Silicones, Sithara Shylaja Nair

Theses and Dissertations

Ice buildup on structures leads to problems that include reduced performance, structural damage and power outages. It is therefore important to limit the energy required for removal of ice from substrates to minimize buildup. Understanding the mechanism of ice adhesion and its dependence on variables like coating thickness, stiffness, surface free energy and morphology is critical for minimizing adhesion. Despite several developments in “icephobic” coatings, which are those that have low ice adhesion, it is important to understand adhesion on the fundamental level to make way for advanced coatings. To do so, a study has been carried out that explores …

Design Of Robust Hydrogel Based On Mussel-Inspired Chemistry, Yuan Liu

Dissertations, Master's Theses and Master's Reports

The structure of catechol is found in mussel adhesive proteins and contributed to both wet-resistant adhesion and cohesive curing of these proteins. A synthetic nano-silicate, Laponite was incorporated into catechol-containing hydrogels and the hydrogel network-bound catechol formed strong reversible interfacial interaction with Laponite. The contribution of incorporated catechol-Laponite reversible interfacial interactions to the mechanics of hydrogels constructed by different strategies was studied. In the first strategy, Laponite and catechol were introduced into the double network hydrogel (DN) via the free radical co-polymerization of a catechol-containing monomer, backbone monomer, and crosslinker. The introduction of catechol-Laponite interactions significantly improved the compressive strength …

A 3d Biomimetic Scaffold Using Electrospinning For Tissue Engineering Applications, Samerender Nagam Hanumantharao

Dissertations, Master's Theses and Master's Reports

Electrospinning holds great promise for designing functional 3D biomimetic scaffolds for tissue engineering applications. The technique allows for the reproducible fabrication of 3D scaffolds with control over the porosity and thickness. In this work, a novel method for the synthesis of a 3D electroactive scaffold using electrospinning from polycaprolactone (PCL), Polyvinylidene Fluoride (PVDF) and Polyaniline (PANI) is reported. Additional scaffolds involving different morphologies of PCL, PCL-PVDF and PCL-PANI-PVDF were also fabricated and evaluated. The scaffolds were characterized using electron microscopy to visualize the morphologies. Infrared spectroscopy was used to confirm the presence of polymers and their respective phases in the …

Electro-Optic Contact Poling Of Polymer Waveguide Devices And Thin Films, Michael Briseno

Dissertations, Master's Theses and Master's Reports

Optical communication is a high speed, large bandwidth, low cost, and power efficient method of transferring data over short-haul and long-haul channels. Optical communication requires devices (optical modulators) that utilize the originating electrical signal information to modulate a corresponding optical signal. State of the art optical modulators can be used for communicating signals at modulation frequencies up to 100 GHz and faster. Polymer modulators are used over lithium niobate due to the large potential electro-optic coefficient, which has been shown to be as high as 226 pm/V in thin films.

Organic electro-optic polymers used in thin film modulators contain nonlinear …

Interactive Physics And Characteristics Of Photons And Photoelectrons In Hyperbranched Zinc Oxide Nanostructures, Garrett Edward Torix

Graduate Theses and Dissertations

As is commonly known, the world is full of technological wonders, where a multitude of electronic devices and instruments continuously help push the boundaries of scientific knowledge and discovery. These new devices and instruments of science must be utilized at peak efficiency in order to benefit humanity with the most advanced scientific knowledge. In order to attain this level of efficiency, the materials which make up these electronics, or possibly more important, the fundamental characteristics of these materials, must be fully understood. The following research attempted to uncover the properties and characteristics of a selected family of materials. Herein, zinc …

The Effect Of Process Parameters And Surface Condition On Bond Strength Between Additively Manufactured Components And Polymer Substrates, Bharat Bhushan Chivukula

Graduate Theses and Dissertations

Additive patching is a process in which printers with multiple axes deposit molten material onto a pre-defined surface to form a bond. Studying the effect of surface roughness and process parameters selected for printing auxiliary part on the bond helps in improving the strength of the final component. Particularly, the influence of surface roughness, as established by adhesion theory, has not been evaluated in the framework of additive manufacturing (AM). A full factorial design of experiments with five replications was conducted on two levels and three factors, viz., layer thickness, surface roughness, and raster angle to examine the underlying effects …

Structure-Property Relationships Of Polyisobutylene-Block-Polyamide Thermoplastic Elastomers, Morgan Dunn Heskett

Master's Theses

Thermoplastic elastomers (TPEs) are a class of polymer fit for a wide variety of applications due to their customizability. In the synthesis of these types of materials, an elastically-performing polymer, deemed the “soft block,” is combined with a stiffer “hard block” polymer, each of which can be selected based on their own specific properties in order to achieve desired material behavior in the final copolymer. Recently, the use of polyisobutylene as a soft block in combination with a polyamide hard block has been investigated for use in TPE synthesis. While the material showed some promising behavior, many properties were still …

Design And Synthesis Of Dynamic Covalent Polymer Scaffolds With Controlled Architectures, Emily Annette Hoff

Dissertations

The design and synthesis of functional, controlled polymer architectures is essential to the development of new materials with precise and tailorable properties or applications. The work described in this dissertation focuses on the development of controlled polymer architectures with dynamic linkages for the design of multifunctional materials and surfaces via robust, efficient, and stimuli-responsive strategies.

In Chapter III, a post-polymerization modification strategy based on ambient temperature nucleophilic chemical deblocking of polymer scaffolds bearing N-heterocycle blocked isocyanate moieties is reported. Room temperature RAFT polymerization of three azole-N-carboxamide methacrylates, including 3,5-dimethyl pyrazole, imidazole, and 1,2,4-triazole derivatives, afforded reactive polymer scaffolds …

Nanostructured Morphologies In Glassy Polymer Networks, Brian Greenhoe

Dissertations

The body of this work describes a novel approach for the dispersion of multi-walled carbon nanotubes in a high T_g epoxy prepolymer matrix using a twin screw high-shear continuous reactor. The method demonstrated improves on previous dispersion methods in several ways. It offers increased efficiency through excellent heat transfer, while being solvent-less, scale-able, and tailorable to drive dispersion states to judiciously chosen dispersion states. Furthermore, it was shown that dispersion state and agglomerate morphology can be directed, in several ways, through processing conditions and also by controlling the matrix viscosity profile through cure. Broadband dielectric spectroscopy, optical hot-stage microscopy, …

Spray Printing Of Organic Semiconducting Single Crystals, Grigorios-Panagiotis Rigas, Marcia M. Payne, John E. Anthony, Peter N. Horton, Fernando A. Castro, Maxim Shkunov

Chemistry Faculty Publications

Single-crystal semiconductors have been at the forefront of scientific interest for more than 70 years, serving as the backbone of electronic devices. Inorganic single crystals are typically grown from a melt using time-consuming and energy-intensive processes. Organic semiconductor single crystals, however, can be grown using solution-based methods at room temperature in air, opening up the possibility of large-scale production of inexpensive electronics targeting applications ranging from field-effect transistors and light-emitting diodes to medical X-ray detectors. Here we demonstrate a low-cost, scalable spray-printing process to fabricate high-quality organic single crystals, based on various semiconducting small molecules on virtually any substrate by …

Molecular Tetrapods For Optoelectronic Applications, Jianzhong Yang

Chemistry and Chemical Biology ETDs

Most conjugated molecules including polymers and small molecules applied in organic solar cells (OSCs) have linear structures containing multiple aromatic groups connected in series. However, unfavorable film forming ability and grain boundaries both originated from high crystallinity of linear small molecules are detrimental to device performances. Thus, among multi-dimensional structures, tetrapodal molecules are especially interesting owing to their unique ability to mutually interlock, which prevents dislodging and provides high structural stabilities. Such molecular design can also increase absorption cross-sections and provide more extensively percolating pathways for charge transport, making such molecular tetrapods promising in OSCs applications. In my dissertation, I …

Study On Mechanical Properties Of Silicone Rubber Materials Used As Gaskets In Pem Fuel Cell Environment, Guo Li

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Analysis Of Optimal Process Conditions And Mechanical Properties On Nanocomposites According To Structural Changes Of Halloysite Nanotubes, Yun-Hae Kim, Soo-Jeong Park, Antonio Norio Nakagaito

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Plasticized Polymer Coatings For Sh-Saw Sensors For High Sensitivity And Long-Term Monitoring Of Btex Analytes In Liquid Phase, Pintu Adhikari

Master's Theses (2009 -)

BTEX compounds (benzene, toluene, ethylbenzene, and xylene) are constituents of crude oil and hazardous to human health. Among them, benzene has the lowest maximum contaminant level for drinking water because of its carcinogenicity. Spills or leakage from underground storage tanks or hazardous waste sites can contaminate nearby groundwater with these volatile organic compounds. Therefore, it is very important to detect the presence of BTEX contamination as early as possible in order to start the remediation process and maintain a healthy environment. To develop an in-situ continuous monitoring sensor system, shear horizontal surface acoustic wave (SH-SAW) sensor devices are being investigated …

Degradation Of Carbon Fiber Reinforced Polymer And Graphite By Laser Heating, Nicholas C. Herr

Theses and Dissertations

The availability of high power, diode pumped solid state and fiber lasers at powers 10 kW and shorter wavelengths (1.07 µm) has invigorated the development of tactical laser weapons. This shift to tactical missions greatly increases the variety of potential targets including carbon fiber reinforced polymers and related materials. The complexity of laser-material interactions has driven a historical reliance on live-fire testing and empirical models, but this becomes more difficult as the number of target materials grow. This dissertation combines thermal imagery and existing thermal models of the fire response of composite materials to develop a hybrid modeling approach of …

Silk As A Biomaterial Paste For Biomimetic Composite, Sang Hyun Park

McKelvey School of Engineering Graduate Student Theses & Dissertations

Silk is a highly promising biomaterial with unique bio-physicochemical properties, such as excellent mechanical and optical properties, biocompatibility and programmable biodegradability. Among many different types, silk from domesticated silkworm, bombyx mori has received wide attention owing to its availability in virtually unlimited quantities and ease of extraction. In this study, we investigated silkworm silk as a protein glue to realize nacre-like composites. We have employed spin assisted layer-by-layer technique to fabricate ultrathin free-standing biocomposite films. Two different composites have been studied: (i) graphene oxide (GO)/silk and (ii) chitin/silk. From our prior work, it is known that the adsorption of amphiphilic …

Study Of Oxidative-Crosslink Reaction In Polyphenyl Sulfide (Pps) / Carbon Fiber And Its Influence In Additive Manufacturing, Dong Hee Kim, Eduardo Barocio, Bastian Brenken, Anthony Favaloro, Byron Pipes

The Summer Undergraduate Research Fellowship (SURF) Symposium

Ever since its development in 1980s, Fused Filament Fabrication (FFF) has been an attractive additive manufacturing technology due to its flexibility to create intricate shapes at lower costs and faster manufacturing process than subtractive techniques. These advantages make FFF suitable for printing molds for use in traditional composites manufacturing processes. Combining FFF with high-temperature thermoplastic composites enables producing molds that not only sustain autoclave conditions but also have low coefficient of thermal expansion (CTE). A semi-crystalline polymer, Poly-phenylene Sulfide (PPS), with 50% by weight of carbon fiber is used as feedstock material for FFF. Nonetheless, PPS is sensitive to undergo …

Characterization Of Suspension Polymerized Polyacrylamide And Poly(Sodium Acrylate-Acrylamide) Copolymer And Their Size Influence On The Properties Of Concrete, Cole R. Davis, Kendra A. Erk, Stacey L. Kelly

The Summer Undergraduate Research Fellowship (SURF) Symposium

Shrinkage leading to cracking and mechanical instability is a major problem for concrete due to the loss of water during the curing process. However, through the addition of Superabsorbent Polymer (SAP) hydrogels, shrinkage can be prevented, increasing the strength of concrete. Characterization of suspension polymerized polyacrylamide (PAM) poly(sodium acrylate-polyacrylamide) (PANa-PAM) copolymer microsphere sizes, morphology and swelling behavior was conducted before adding them to concrete. Size was determined using microscopy paired with ImageJ analysis. Coulter Counter size characterization was also used to determine the particle size distribution. Swelling behavior was determined using the tea bag method as well as size analysis …