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Articles 1 - 7 of 7
Full-Text Articles in Materials Science and Engineering
Engineering High Performance Epoxy Thermosets Using Next-Generation Impact Modification, Madhura Pawar
Engineering High Performance Epoxy Thermosets Using Next-Generation Impact Modification, Madhura Pawar
Doctoral Dissertations
Optimization of fracture toughness of high Tg 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 Rp 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
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 …
Swelling Induced Deformation Of Thermally Responsive Hydrogels, Ying Zhou
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
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
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 …
Engineering Next Generation Anisotropic Materials And Composites, Nihal Kanbargi
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 …
Role Of Rigidity And Flexibility Of Functional Groups Within The Interior Of Supramolecular Assemblies And Their Implications, Oyuntuya Munkhbat
Role Of Rigidity And Flexibility Of Functional Groups Within The Interior Of Supramolecular Assemblies And Their Implications, Oyuntuya Munkhbat
Doctoral Dissertations
Engineering of supramolecular assemblies at molecular level renders functional nanomaterials that present explicit response to certain environmental changes. Systematic structure-property correlation studies will unravel the fundamental design constraints of these functional nanomaterials that fulfill the emergent need. This dissertation will primarily focus on understanding the role of rigidity and flexibility of functional groups within amphiphilic assemblies and employing this basic concept in drug delivery and diagnostics applications. Supramolecular assemblies formed by amphiphilic dendrimers and polymers are preferred for this study as they exhibit high thermodynamic stability and structural flexibility. The role of aromatic interaction on the unimer-aggregate dynamic equilibrium was …