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Articles 1 - 19 of 19
Full-Text Articles in Engineering
The Rheology And Roll-To-Roll Processing Of Shear-Thickening Particle Dispersions, Sunilkumar Khandavalli
The Rheology And Roll-To-Roll Processing Of Shear-Thickening Particle Dispersions, Sunilkumar Khandavalli
Doctoral Dissertations
Particle dispersions are ubiquitous in our daily lives ranging from food and pharmaceutical products to inks. There has been great interest in the recent years in formulation of functional inks to fabricate myriad flexible electronic devices through high-throughput roll-to-roll technologies. The formulations often contain several functional additives or rheological modifiers that can affect the microstructure, rheology and processing. Understanding the rheology of formulations is important for tuning the formulation for optimal processing. This thesis presents investigations on the rheology of particle dispersions and their impact on roll-to-roll technologies. Shear-thickening behavior is common in particle dispersions, particularly, concentrated particulate inks. We …
The Role Of Chain Configuration In Governing The Rational Design Of Polymers For Adhesion, Onyenkachi Wamuo
The Role Of Chain Configuration In Governing The Rational Design Of Polymers For Adhesion, Onyenkachi Wamuo
Doctoral Dissertations
ABSTRACT THE ROLE OF CHAIN CONFIGURATION IN GOVERNING THE RATIONAL DESIGN OF POLYMERS FOR ADHESION SEPTEMBER 2017 ONYENKACHI C. WAMUO, B.Eng., FEDERAL UNIVERSITY OF TECHNOLOGY, OWERRI (FUTO), NIGERIA M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Shaw Ling Hsu The chain configurational control of polymers used in adhesion can be utilized as a means of tuning the cohesive properties of hot melt adhesives (HMAs). The cohesive properties control the solidification, strength, setting speed. Propylene-Ethylene copolymers (PP-co-PE) and thermoplastic polyurethanes (TPUs) were studied. In the first project, the effects of sequence distribution of the two types …
Computational Studies Of Structure–Function Relationships Of Supported And Unsupported Metal Nanoclusters, Hongbo Shi
Computational Studies Of Structure–Function Relationships Of Supported And Unsupported Metal Nanoclusters, Hongbo Shi
Doctoral Dissertations
Fuel cells have been demonstrated to be promising power generation devices to address the current global energy and environmental challenges. One of the many barriers to commercialization is the cost of precious catalysts needed to achieve sufficient power output. Platinum-based materials play an important role as electrocatalysts in energy conversion technologies. In order to improve catalytic efficiency and facilitate rational design and development of new catalysts, structure–function relationships that underpin catalytic activity must be understood at a fundamental level. First, we present a systematic analysis of CO adsorption on Pt nanoclusters in the 0.2-1.5 nm size range with the aim …
Analyses Of Densely Crosslinked Phenolic Systems Using Low Field Nmr, Jigneshkumar Patel
Analyses Of Densely Crosslinked Phenolic Systems Using Low Field Nmr, Jigneshkumar Patel
Doctoral Dissertations
A uniform dispersion of reactants is necessary to achieve a complete reaction involving multi-components, especially for the crosslinking of rigid high-performance materials. In these reactions, miscibility is crucial for curing efficiency. This miscibility is typically enhanced by adding a third component, a plasticizer. For the reaction of the highly crystalline crosslinking agent hexamethylenetetramine (HMTA) with a strongly hydrogen-bonded phenol formaldehyde resin, furfural has been traditionally used as the plasticizer. However, the reason for its effectiveness is not clear. In this doctoral thesis work, miscibility and crosslinking efficiency of plasticizers in phenolic curing reactions are studied by thermal analysis and spectroscopic …
Nanocomposite Polymer Networks For Reconfigurable Materials, Adam W. Hauser
Nanocomposite Polymer Networks For Reconfigurable Materials, Adam W. Hauser
Doctoral Dissertations
This thesis broadly aims to design reconfigurable materials through complementary combinations of nanoparticles and polymers. Understanding nanoparticle dispersion pathways and mechanisms is a critical first step in any polymer nanocomposite work as it continues to be a non-trivial subject. To this end, Chapter 2 describes a simple method to control nanoparticle dispersion within polymer melts by photografting random copolymers to selectively reactive nanoparticle ligands. The chapters following focus on harnessing the functionality of well dispersed nanocomposite networks to elicit macro-scale responses. Chapter 3 exploits the unique optical properties of gold nanoparticles in combination with thermally responsive hydrogels and liquid crystalline …
Modeling Of Nanoscale Transport In Mesoporous Membranes, Ashutosh Rathi
Modeling Of Nanoscale Transport In Mesoporous Membranes, Ashutosh Rathi
Doctoral Dissertations
Mesoporous membranes with pore sizes in the range 2-50 nm provide an energy efficient alternative for separation of mixtures such as CO2 from stack effluents and volatile organic compounds (VOC) from air. Transport mechanisms such as capillary condensation, Knudsen diffusion and surface adsorption help in enrichment of a more condensable component based on the bulk mixture thermodynamics, surface chemistry and geometry of the mesopores. Despite the progress in synthesis techniques, design of better mesoporous materials for targeted separations is still a challenge due to the absence of clear design rules. Modeling techniques can be used to quantify the relevant …
Metabolic Modeling And Engineering Of Gas Fermentation In Bubble Column Reactors, Jin Chen
Metabolic Modeling And Engineering Of Gas Fermentation In Bubble Column Reactors, Jin Chen
Doctoral Dissertations
Gas fermentation is an attractive route to produce alternative fuels and chemicals from non-food feedstocks, such as waste gas streams from steel mills and synthesis gas (mainly CO and H2) produced from municipal solid waste through gasification. While commercial development of gas fermentation technology is underway, many research problems must be addressed to further advance the technology towards economic competitiveness. A particularly important challenge is to develop integrated metabolic and transport models that describe gas fermentation in industrially relevant bubble column reactors. I have developed and evaluated a spatiotemporal metabolic model for bubble column reactors with the syngas …
Interactions At The Aqueous Interface Of Large-Area Graphene: Colloidal-Scale And Protein Adsorption, Aaron Chen
Interactions At The Aqueous Interface Of Large-Area Graphene: Colloidal-Scale And Protein Adsorption, Aaron Chen
Doctoral Dissertations
This thesis addresses the interactive interfacial character of large-area supported graphene in an aqueous environment near neutral pH. Studies of molecular bio-interactions with proteins and colloidal interactions with microparticles probe the role of hydrophobicity, van der Waals, and electrostatic contributions with varied ionic strength. The respective roles of the silica support and the graphene itself are identified. Results are benchmarked against other systems directly in experiments, and against published behavior with other materials, especially self-assembled monolayers. The adhesive and adsorption behavior of supported graphene is also put into context by calculations of surface and interaction potentials. Interest in graphene is …
Nanoporous Solid Acid Materials For Biomass Conversion Into Value-Added Chemicals: Synthesis, Catalysis, And Chemistry, Hong Je Cho
Doctoral Dissertations
Growing environmental concerns associated with diminishing reserves of fossil fuels has led to accelerated research efforts towards the discovery of new catalytic processes for converting renewable lignocellulosic biomass into value-added chemicals. For this conversion, nanoporous solid acid materials have been widely used because of their excellent hydrothermal stability and molecular sieving capability. In the thesis, hierarchical Lewis acid zeolites with ordered mesoporosity and MFI topology (three dimensionally ordered mesoporous imprinted (3DOm-i) Sn-MFI) were successfully synthesized within the confined space of three dimensionally ordered mesoporous (3DOm) carbon by a seeded growth method. The obtained 3DOm-i Sn-MFI showed at least 3 times …
Vitreous Gel Physics, Svetlana Morozova
Vitreous Gel Physics, Svetlana Morozova
Doctoral Dissertations
The transparent vitreous, which fills the posterior cavity of the eye, is incredibly engineered. The charged polyelectrolyte hyaluronic acid (HA) network swells to maintain the pressure in the eye, while stiff collagen type II bundles help absorb any external mechanical shock. Our investigations have contributed to a few key developments related to the physical properties of the vitreous: (1) The stiff collagen network that supports the soft gel network is self-assembled from single triple-helix collagen proteins. Electrostatic interactions drive this assembly, such that the size and concentration are optimized at physiological salt concentrations. The width of the assemblies remarkably changes …
The Self-Assembly Of Lamellae-Forming Block Copolymer For High Resolution Nanolithography, Zhiwei Sun
The Self-Assembly Of Lamellae-Forming Block Copolymer For High Resolution Nanolithography, Zhiwei Sun
Doctoral Dissertations
This thesis will be focused on the thin film self-assembly and high resolution nanolithography of lamellae-forming PS-b-P2VP block copolymer. Some of the scientific and engineering problems of block copolymer self-assembly will be studied using the state-of-the-art characterization facilities including AFM, SEM and synchrotron radiation X-ray scattering, pushing forward the application of block copolymer in high resolution nanolithography, storage media, and separation membranes, etc. The first challenge is the design of BCP with small domain spacing, which defines the resolution of BCP nanolithography. Small domain spacing can be achieved by reducing the degree of polymerization, but order-to-disorder transition happens …
Deformation And Adhesion Of Soft Composite Systems For Bio-Inspired Adhesives And Wrinkled Surface Fabrication, Michael Imburgia
Deformation And Adhesion Of Soft Composite Systems For Bio-Inspired Adhesives And Wrinkled Surface Fabrication, Michael Imburgia
Doctoral Dissertations
The study of soft material deformation and adhesion has broad applicability to industries ranging from automobile tires to medical prosthetics and implants. When a mechanical load is imposed on a soft material system, a variety of issues can arise, including non-linear deformations at interfaces between soft and rigid components. The work presented in this dissertation embraces the occurrence of these non-linear deformations, leading to the design of functional systems that incorporate a soft elastomer layer with application to bio-inspired adhesives and wrinkled surface fabrication. Understanding the deformation of a soft elastomer layer and how the system loading and geometry influence …
Synthesis Of Biopolymer Materials Tailored For Biological Applications, Nathan P. Birch
Synthesis Of Biopolymer Materials Tailored For Biological Applications, Nathan P. Birch
Doctoral Dissertations
Biopolymers are able to address a wide variety of medical concerns from chronic wounds to stem cell cultivation to antibacterial and antifouling applications. They are non-toxic, biodegradable, and biocompatible, making them ideal candidates for creating green materials for biological applications. In this thesis, we cover the synthesis of two novel materials from the biopolymers, chitosan and pectin. Chitosan is a biocompatible antibacterial polycation and pectin is an anti-inflammatory polyanion with a strong propensity for hydrogen-bonding. The two chitosan:pectin materials, particles and hydrogels, explore some of the structures that can be created by tuning the electrostatic interactions between chitosan and pectin. …
Rheological Characterization Of Liquid-To-Solid Transitions In Bulk Polyelectrolyte Complexes, Yalin Liu, Brian Momani, H. Henning Winter, Sarah L. Perry
Rheological Characterization Of Liquid-To-Solid Transitions In Bulk Polyelectrolyte Complexes, Yalin Liu, Brian Momani, H. Henning Winter, Sarah L. Perry
Chemical Engineering Faculty Publication Series
Polyelectrolyte complexation has long been known to result in both liquid and solid complexes. However, the exact nature of the liquid-to-solid transition remains an open question. We have used rheology to explain this phenomenon for the model system of poly(4-styrenesulfonic acid, sodium salt) (PSS) and poly(diallyldimethyl ammonium chloride) (PDADMAC) in the presence of potassium bromide (KBr). The use of a time-salt superposition allows for a detailed analysis of changes in the linear viscoelastic response for both liquid complex coacervates and solid polyelectrolyte complexes as a function of salt concentration, and facilitates unambiguous determination of the mechanism for this phase transition. …
The Effect Of Comb Architecture On Complex Coacervation, Brandon M. Johnston, Cameron W. Johnston, Rachel A. Letteri, Tyler K. Lytle, Charles E. Sing, Todd Emrick, Sarah L. Perry
The Effect Of Comb Architecture On Complex Coacervation, Brandon M. Johnston, Cameron W. Johnston, Rachel A. Letteri, Tyler K. Lytle, Charles E. Sing, Todd Emrick, Sarah L. Perry
Chemical Engineering Faculty Publication Series
Complex coacervation is a widely utilized technique for effecting phase separation, though predictive understanding of molecular-level details remains underdeveloped. Here, we couple coarse-grained Monte Carlo simulations with experimental efforts using a polypeptide-based model system to investigate how a comb-like architecture affects complex coacervation and coacervate stability. Specifically, the phase separation behavior of linear polycation-linear polyanion pairs was compared to that of comb polycation-linear polyanion and comb polycation-comb polyanion pairs. The comb architecture was found to mitigate cooperative interactions between oppositely charged polymers, as no discernible phase separation was observed for comb-comb pairs and complex coacervation of linear-linear pairs yielded stable …
A Student-Created, Open Access, Living Textbook, Sualyneth Galarza, Sarah L. Perry, Shelly Peyton
A Student-Created, Open Access, Living Textbook, Sualyneth Galarza, Sarah L. Perry, Shelly Peyton
Chemical Engineering Faculty Publication Series
Textbooks are expensive, updated infrequently, and rarely used effectively by students. We discuss here a way for students to create the textbook for the course, helping them feel ownership over the course material. This Wiki-based, student-created textbook is online free for use, widely accessible by all, and editable during the course of and as topics evolve. This type of textbook format is particularly well suited to upper-level electives on topics that are rapidly emerging. We have nucleated a student created textbook here, fully online and open access, for two upper elective courses in chemical engineering. Wikis offer an easy-to-learn platform …
Microfluidics: From Crystallization To Serial Time-Resolved Crystallography, Shuo Sui, Sarah L. Perry
Microfluidics: From Crystallization To Serial Time-Resolved Crystallography, Shuo Sui, Sarah L. Perry
Chemical Engineering Faculty Publication Series
Capturing protein structural dynamics in real-time has tremendous potential in elucidating biological functions and providing information for structure-based drug design. While time-resolved structure determination has long been considered inaccessible for a vast majority of protein targets, serial methods for crystallography have remarkable potential in facilitating such analyses. Here, we review the impact of microfluidic technologies on protein crystal growth and X-ray diffraction analysis. In particular, we focus on applications of microfluidics for use in serial crystallography experiments for the time-resolved determination of protein structural dynamics.
Sequence And Entropy-Based Control Of Complex Coacervates, Li-Wei Chang, Tyler K. Lytle, Mithun Radhakrishna, Joel J. Madinya, Jon Vélez, Charles E. Sing, Sarah L. Perry
Sequence And Entropy-Based Control Of Complex Coacervates, Li-Wei Chang, Tyler K. Lytle, Mithun Radhakrishna, Joel J. Madinya, Jon Vélez, Charles E. Sing, Sarah L. Perry
Chemical Engineering Faculty Publication Series
Biomacromolecules rely on the precise placement of monomers to encode information for structure, function, and physiology. Efforts to emulate this complexity via the synthetic control of chemical sequence in polymers are finding success; however, there is little understanding of how to translate monomer sequence to physical material properties. Here we establish design rules for implementing this sequence-control in materials known as complex coacervates. These materials are formed by the associative phase separation of oppositely charged polyelectrolytes into polyelectrolyte dense (coacervate) and polyelectrolyte dilute (supernatant) phases. We demonstrate that patterns of charges can profoundly affect the charge–charge associations that drive this …
Strain-Stiffening Gels Based On Latent Crosslinking, Yen H. Tran, Matthew J. Rasmuson, Todd Emrick, John Klier, Shelly Peyton
Strain-Stiffening Gels Based On Latent Crosslinking, Yen H. Tran, Matthew J. Rasmuson, Todd Emrick, John Klier, Shelly Peyton
Chemical Engineering Faculty Publication Series
Gels are an increasingly important class of soft materials with applications ranging from regenerative medicine to commodity materials. A major drawback of gels is their relative mechanical weakness, which worsens further under strain. We report a new class of responsive gels with latent crosslinking moieties that exhibit strain-stiffening behavior. This property results from the lability of disulfides, initially isolated in a protected state, then activated to crosslink on-demand. The active thiol groups are induced to form inter-chain crosslinks when subjected to mechanical compression, resulting in a gel that strengthens under strain. Molecular shielding design elements regulate the strain-sensitivity and spontaneous …