Polymer and Organic Materials Commons^™

Inter-Droplet Membranes For Mechanical Sensing Applications, Nima Tamaddoni Jahromi

Doctoral Dissertations

This dissertation combines self-assembly phenomena of amphiphilic molecules with soft materials to create and characterize mechanoelectrical transducers and sensors whose sensing elements are thin-film bioinspired membranes comprised of phospholipids or amphiphilic polymers. We show that the structures of these amphiphilic molecules tune the mechanical and electrical properties of these membranes. We show that these properties affect the mechanoelectrical sensing characteristic and range of operation of these membrane transducers. In the experiments, we construct and characterize a membrane-based hair cell embodiment that enables the membrane to be responsive to mechanical perturbations of the hair. The resulting oscillations of membranes formed between …

Study Of Magneto-Optical Behaviors At A Ferromagnetic/Organic Semiconductor Interface, Jeremy Tyler Tisdale

Masters Theses

Organic materials have been widely studied for the last 20 years to use for photovoltaic applications. Organic photovoltaic materials have shown promising properties for solar cells, such as very low cost, flexibility, easy fabrication methods, etc. Although power conversion efficiencies for organic-based solar cells have exponentially grown in the last decade, up to about 13% in early 2016, it is still optimal to increase these efficiencies. In order to raise efficiencies, it is important to study the fundamental mechanisms inside organic materials that lead to photovoltaic properties. This thesis reports the magneto-optical effects on the p-type organic semiconductor, tetracene, from …

Synthesis Of Acceptors For Use In Donor-Acceptor Copolymers And Characterization Of These Polymers, William D. Walker

Honors Theses

In this thesis, a selenium-derivatized acceptor was synthesized to examine the heavy atom effects of selenium on the position of the frontier molecular orbitals (HOMO/LUMO band gap) as opposed to sulfur in a donor-acceptor copolymer for use in light harvesting and detection applications. Over the course of this research, standard operating protocols for ultraviolet-visible (UV-Vis-NIR) and Fourier transform infrared (FT-IR) spectroscopies, as well as cyclic voltammetry (CV) characterization techniques were established. Once synthesized, the polymers were characterized through use of the established characterization protocols. The selenium-derivatized polymer exhibited a bathochromic shift compared to the sulfur analogue, with a solid-state absorption …

The Effect Of Cure Rate On Glassy Polymer Networks, Kristen M. Van De Voorde

Honors Theses

The formation of glassy polymer networks such as epoxy-amine systems may be altered by varying the temperature ramp rate that is used to cure the system. As a result, the physical and mechanical properties of the network may be changed. This work synthesized the epoxy resins diglycidyl ether of bisphenol A (DGEBA) with the amine curing agent 4,4-diaminodiphenyl sulfone (4,4’-DDS) from 35°C to 180°C using varying temperature ramp rates. Mechanical and structural properties of these samples were then analyzed to determine the effect the different temperature ramp rates had on the formation and properties of the thermoset matrix. These aspects …

Engineered Quantum Dots For Eva Nanocomposite Films And Tio2 Photocatalysts, Md Abdul Mumin

Electronic Thesis and Dissertation Repository

Light absorbing inorganic nanoparticles in transparent plastics such as poly(ethylene-co-vinyl acetate) (EVA) are of enormous interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light. However, how to stabilize the QDs for long product life spans without "blinking" while enabling their easy integration into polymer systems is lacking. This work examines different approaches for loading mesoporous silica encapsulated QDs into EVA polymer films which can control plant growth in greenhouses or enhance PV panel efficiencies.

Highly luminescent CdS and CdS-ZnS core-shell QDs …

Solution, Interfacial, And Interlayer Studies Of Electronically Active Polymers, Hsin-Wei Wang

Doctoral Dissertations

This thesis describes the solution behavior and interfacial properties of electronically active polymers. The performance of such polymers in devices is often determined by their chain conformation and morphology in solution and in thin films. For example, the intricate balance between polymer domain size and crystalline packing of electron donor and acceptor components, as well as the properties at the polymer-metal interface, are crucial for achieving optimal performance in devices, such as solar cells. Chapter 1 presents the current progress in polymer-based solar cells, their fundamental principles, and key factors to improve their efficiency. Literature precedents on the development of …

Diffusion Of Polymers In Polyelectrolyte Gels, Anand Rahalkar

Doctoral Dissertations

Polyelectrolyte gels have the ability to undergo volume transitions in response to external stimuli. As a result, they are used in a wide variety of applications such as sensors, actuators, artificial implants, and controlled drug delivery. In addition, diffusion of trapped macromolecules inside gels is of tremendous significance in drug delivery systems. In this thesis, the dynamics of trapped polyelectrolytes in a polyelectrolyte gel is studied using dynamic light scattering technique. The effect of the crosslink density and the charge density of the gel, as well as of solvent quality and salt concentration are investigated. In general, two distinct diffusive …

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 …

Model Systems For Characterizing The Intrinsic Properties Of Polymer Semiconductors: Oligomers And Single Crystals, Nicholas S. Colella

Doctoral Dissertations

Polymer semiconductors hold great promise for the realization of inexpensive, flexible electronic devices. One of the greatest strengths of these materials, their low-cost processability from solution, results in a wide range of solid-state structures. The crystallinity and morphology of these materials strongly impacts their performance as charge carriers. Furthermore, the nature of polymerization inherently leads to the production of materials which are disperse in their molecular character, with regard to both coupling and molecular weight. Thus, it is difficult to deconvolute the intrinsic properties of polymer semiconductors from their synthetic and processing conditions. Polythiophenes are particularly susceptible to performance variations …

Controlling The Assembly Of Nanoparticles In Polymer Blends, Kyle C. Bryson

Doctoral Dissertations

While many novel methods have been devised for directing the assembly of nanoparticles in block copolymers, the topic has not reached the same level of sophistication for polymer blends. The assembly of particles at the interface between phase-separated domains can serve as a means to compatibilize polymer blends, reducing domain sizes and enhancing interdomain adhesion by impeding coalescence and decreasing interfacial tension. Compatibilization optimizes the performance of blended materials in applications where the properties of both components must be expressed synergistically, such as in plastics requiring both high strength and high toughness and in photovoltaic films. Thus, approaches to robustly …

Tribological Performance Of Hybrid Filtered Arc-Magnetron Coatings: Part I: Coating Deposition Process And Basic Coating Properties Characterization, Vladimir Gorokovsky, Chris Bowman, Paul Gannon, David Vanvorous, Andrey Voevodin, Adam Rutkowski, Christopher Muratore, Richard Smith, Asghar Kayani, David Gelles, Vaithiyalingam Shutthanandan, Boris Trusov

Christopher Muratore

Aircraft propulsion applications require low-friction and wear resistant surfaces that operate under high contact loads in severe environments. Recent research on supertough and low friction nanocomposite coatings produced with hybrid plasma deposition processes was demonstrated to have a high potential for such demanding applications. However, industrially scalable hybrid plasma technologies are needed for their commercial realization. The Large area Filtered Arc Deposition (LAFAD) process provides atomically smooth coatings at high deposition rates over large surface areas. The LAFAD technology allows functionally graded, multilayer, super-lattice and nanocomposite architectures of multi-elemental coatings via electro-magnetic mixing of two plasma flows composed of different …

Progress In The Development Of Adaptive Nitride-Based Coatings For High Temperature Tribological Applications, Samir Aouadi, Brandon Luster, Punit Kohli, Christopher Muratore, Andrey Voevodin

Christopher Muratore

Adaptive tribological coatings were recently developed as a new class of smart materials that were designed to adjust their surface chemical composition and structure as a function of changes in the working environment to minimize friction coefficient and wear between contact surfaces. This paper provides an overview of the current research developments in this field, including: (1) Chameleon nanocomposite coatings which are produced by depositing a multi-phase structure whereby some of the phases provide mechanical strength and others are lubricious; (2) Micro- and nano-textured coatings which consist of hard nitride films with highly ordered micropores and nanopores that are subsequently …

Plasma Enhanced Surface Treatments Using Electron Beam-Generated Plasmas, Darrin Leonhardt, Christopher Muratore, Scott Walton, Robert Meger

Christopher Muratore

NRL has developed a ‘large area plasma processing system’ (LAPPS) utilizing a high energy (∼2 keV) modulated electron beam to drive the plasma ionization. This system has been shown to be (1) efficient at producing plasma in any gas composition, (2) capable of producing low temperature plasma electrons (9–10¹² cm⁻³) and (3) scalable to large area (square meters). In this work, the progress of a number of applications using LAPPS is discussed. Nitride growth in stainless steel was investigated, which demonstrated high rates (up to 20 μm/h^1/2) at low temperatures (≤462 °C). Complementary mass spectrometry …

Molybdenum Disulfide As A Lubricant And Catalyst In Adaptive Nanocomposite Coatings, Christopher Muratore, Andrey Voevodin

Christopher Muratore

Nanocomposite YSZ–Ag–Mo–MoS₂ coatings with different MoS₂ additions (0–100 at.%) were deposited with a hybrid pulsed laser/magnetron sputtering/filtered cathodic arc process. Wear testing was performed from 25 to 700 °C for each of the coatings. Electron microscopy and other characterization techniques were used to examine the surfaces and wear tracks of the coatings and to determine the mechanisms resulting in the measured tribological properties. Adaptive coatings containing 8 at.% MoS₂demonstrated a friction coefficient of 0.2 throughout the temperature range examined here, compared to 0.4 for YSZ–Ag–Mo with no MoS₂. Characterization of the YSZ–Ag–Mo–8% MoS_{2 …}

In Situ Studies Of Tic1−X N X Hard Coating Tribology, Marisa Rebelo De Figueiredo, Christopher Muratore, Robert Franz, Richard Chromik, Kathryn Wahl, Andrey Voevodin, Michel O'Sullivan, Markus Lechthaler, Christian Mitterer

Christopher Muratore

TiC1−x N x hard coatings present time-dependent tribological behavior with an initial running-in period (500–2000 cycles) marked by an elevated friction coefficient, followed by >10000 cycles with low-friction and wear at room temperature (RT) in ambient air. The mechanisms behind this behavior are not completely understood. Tribological tests performed at RT and at different relative humidity (RH) levels revealed that a minimum value between 15 and 25% RH is needed to trigger the low-friction regime at a sliding speed of 100 mm s−1. By in situ observations of transfer film growth, it could be observed that third body material …

Adaptive Nanocomposite Coatings With A Titanium Nitride Diffusion Barrier Mask For High-Temperature Tribological Applications, Christopher Muratore, Jianjun Hu, Andrey Voevodin

Christopher Muratore

Adaptive nanocomposite coatings that demonstrate low friction throughout broad ranges of temperature, wear, humidity and other environments are currently in development. One effective temperature adaptation mechanism at temperatures ≤ 500 °C is diffusion of noble metal to the coating surface, providing a low shear strength interface at the friction contact supported by a hard surface underneath. To prolong the wear lifetime of chameleon coatings relying upon this mechanism for low friction, a coating architecture incorporating a diffusion barrier mask to inhibit noble metal diffusion was employed. The diffusion barrier-capped coating provided lubrication at 500 °C over ten times longer than …

A Simultaneous Increase In The Thermal And Electrical Transport In Carbon Nanotube Yarns Induced By Inter-Tube Metallic Welding, Sabyasachi Ganguli, Amber Reed, Chaminda Jayasinghe, Joe Sprengard, Ajit Roy, Andrey Voevodin, Christopher Muratore

Christopher Muratore

Vertically aligned arrays of multiwall carbon nanotubes (MWCNT) were decorated with gold (Au) nanoparticles of different diameter and areal densities and spun into yarns. The melting point of Au nanoparticles determined by differential scanning calorimetry was approximately 260 °C, well below the oxidation temperature of carbon. A continuous yarn was formed while pulling out a bundle of CNTs from the metalized CNT array. Relatively low temperature (300 °C) thermal processing of the metalized yarn resulted in a 30% improvement in thermal conductivity, 40% increase in electrical conductivity and a 4× increase in elastic modulus. Cross-sections of the yarn were examined …

Biopolymeric Mucin And Synthetic Polymer Analogs: Their Structure, Function And Role In Biomedical Applications, Sundar Prasanth Authimoolam, Thomas D. Dziubla

Chemical and Materials Engineering Faculty Publications

Mucin networks are viscoelastic fibrillar aggregates formed through the complex self-association of biopolymeric glycoprotein chains. The networks form a lubricious, hydrated protective shield along epithelial regions within the human body. The critical role played by mucin networks in impacting the transport properties of biofunctional molecules (e.g., biogenic molecules, probes, nanoparticles), and its effect on bioavailability are well described in the literature. An alternate perspective is provided in this paper, presenting mucin’s complex network structure, and its interdependent functional characteristics in human physiology. We highlight the recent advances that were achieved through the use of mucin in diverse areas of bioengineering …

Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott Walton, D. Leonhardt, Richard Fernsler

Christopher Muratore

A hybrid plasma enhanced physical vapor deposition (PEPVD) system consisting of an unbalanced dc magnetron and a pulsed electron beam-produced plasma was used to deposit reactively sputteredtitanium nitride thin films. The system allowed for control of the magnitudes of the ion and neutral flux, in addition to the type of nitrogen ions (atomic or molecular) that comprised the flux. For all deposition experiments, the magnitude of the ion flux incident on the substrate was held constant, but the composition of the total flux was varied. X-ray diffraction and atomic force microscopy showed that crystallographic texture and surface morphology of the …