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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 40 for “"hard segment"”.
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PEO-containing copolymers as polyurethane soft segments in the development of high performance materials
Silk-inspired segmented polyurethanes containing flexible, hydrophilic segments with crystalline and liquid crystalline moieties were developed to mimic the hierarchical morphology of the continuous domain in and the superior mechanical properties of native spider silk. A series of polyurethane …
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Morphology of water-blown flexible polyurethane foams
… of phase separation is independent of water (hard segment) content. In the foam with the lowest water content the morphology is similar to that of typical segmented urethane elastomers. Small hard segment domains are present with a correlation distance of roughly 7.0 nanometers. When the water …
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Moisture-Cure Polyurethane Wood Adhesives: Wood/Adhesive Interactions and Weather Durability
… significant PURs (CPURs) with different hard segment contents were prepared. Separately, an early side project involved the synthesis of a 13C and 15N double-labeled polymeric methylenebis(phenylisocyanate) (pMDI) resin; this was used for the solid-state NMR characterization of isocyanate …
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Synthesis and characterization of ammonium ionenes containing hydrogen bonding functionalities
… Novel adenine and thymine functionalized segmented and non-segmented ammonium ionenes were successfully synthesized using Michael addition chemistry. In non-segmented systems, we investigated the influence of spacer length on homoassociation and heteroassociation of complementary …
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Investigation of the Influence of Selected Variables on the Solid State Structure-Property Behavior of Segmented Copolymers
Segmented copolymers are a commercially important class of materials that are utilized in a wide variety of applications. In these systems a relatively large number of variables such as backbone chemistry, segment molecular weight, and the overall molecular weight of the copolymer can be …
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Structural and viscoelastic studies of flexible polyurethane foams
… cross-links and urea based phase separated hard segment domains) were evaluated. It was discovered that the structure of the hard segment domains dictated the foam's behavior, especially at elevated temperatures and humidity. Furthermore, it was found that the hard segment domains in …
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Structure-property relationships in segmented copolymers
The structure-property relationships for various segmented copolymers were investigated. A number of mechanical and thermal characteristics were determined. The morphology was characterized by SAXS with respect to size and dispersion of domains; degree of phase separation and the domain interfacial …
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Structure–Property Relationships Of: 1) Novel Polyurethane and Polyurea Segmented Copolymers and 2) The Influence of Selected Solution Casting Variables on the Solid State Structure of Synthetic Polypeptide Films Based on Glutamate Chemistry
… dissertation concern the characterization of segmented polyurethanes and polyureas synthesized without the use of chain extenders'molecules that are typically used to promote a microphase separated morphology that gives these materials their useful characteristics. Polyurethanes in which a …
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Structure-Property Relationships of Flexible Polyurethane Foams
… nm across. Aggregations of these lamellae-like hard domains may be the polyurea balls typically observed via TEM. Diethanolamine, a widely used cross-linking agent in molded foams, was shown to disrupt ordering in the polyurea hard domains and alter the interconnectivity of hard domains by …
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Design, synthesis and characterization of side chain liquid crystal segmented polyurethanes
… of polyurethanes are made with traditional hard segments and cyano-biphenyl mesogens pendant on the soft segment. The synthesis of the soft segment macrodiol. a carbinol endcapped hydromethylsiloxane oligomer that can be functionalized with mesogen via a hydrosilylation technique, is …
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Determining soft segment structure-property effects in the enhancement of segmented polyurethane performance
Liquid Crystalline Elastomer (LCE)-inspired segmented polyurethane elastomers possessing widely different extents of ordering were created to mimic the hierarchical structure of the continuous matrix and superior mechanical performance of spider silk fibers. The silk's remarkable toughness …
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Characterization of Structure-Property Relationships of Poly(urethane-urea)s for Fiber Applications
… poly(tetramethylene ether glycol) as soft segments. Recent developments in catalyst technology have resulted in the production of ultra-low monol content poly(propylene glycol) (PPG), which is nearly difunctional (f=1.95+). This enhancement in difunctionality has potentially enabled the use …
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Tailored Architectures of Ammonium Ionenes
… endothelial cell line. A series of low hard segment (HS) content, poly(propylene glycol) (PPG)-based ammonium ionenes were synthesized using a Menshutkin reaction from bromine end-capped PPG oligomers (prepared using acid-chloride reactions) and N,N,Nâ ²,Nâ …
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Non-covalent Intermolecular Interactions in Polymer Design: Segmented Copolymers to Non-viral Gene Delivery Vectors
… the properties of a given system, from segmented copolymers to interactions of functionalized polymers with non-viral nucleic acids delivery vehicles. The ability to control the intermolecular interactions of a given system allow for tailoring of that system to yield a desired outcome, …
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Advancing Step-Growth Polymers: Novel Macromolecular Design and Electrostatic Interactions in Polyesters and Polyurethanes
… successfully synthesized high molecular weight segmented copolyesters. The cycloaliphatic monomers 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) and dimethyl-1,4-cyclohexane dicarboxylate (DMCD) afforded sterically hindered, ester carbonyls in high-Tg polyester precursors. Reaction between the …
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Synthesis and Characterization of Novel Polyethers and Polydimethylsiloxanes for Use in Biomaterials
… as well as PDMS-based ionenes with different hard segment groups.
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Design of Functional Polyesters for Electronic and Biological Applications
… bisphenol-A replacements and ioncontaining segmented polyurethanes aided in identifying benchmark polymers, including limitations, challenges, and future needs. Structure-property-morphology relationships were investigated to evaluate the polymers for success in the proposed applications as …
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Step-Growth Polymerization Towards the Design of Polymers: Assembly and Disassembly of Macromolecules
… chemistry was used to synthesize polyesters and segmented block copolyesters. Triazole-containing homopolyesters exhibited a marked increase (~40 °C) in Tg, relative to structurally analogous classical polyesters synthesized in the melt. However, the triazole-containing homopolyesters exhibited …
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Viscoelastic behavior of water-blown flexible polyurethane foams
… water-blown polyurethane foams with varying hard segment content as well as solid plaques made from these foams. Three viscoelastic tests; tensile stress relaxation, compression load relaxation, and compression creep, were utilized to evaluate the behavior of these materials at constant …
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Thermomechanics of nano-filled elastomers
… is possible to preferentially nanoreinforce the hard micro-domains of thermoplastic elastomers with smectic clay nanofillers that have characteristic dimensions similar to the hard segment. The adhesion between the clay and the hard micro-domains coupled with the formation of a percolative …
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