Browsing by Subject "Thermoplastic Elastomer"

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    Block Copolymers for Sustainable Thermoplastic Elastomers and Nanoparticle Fabrication
    (2017-12) Nasiri, Mohammadreza
    The first part of this thesis focuses on the preparation and characterization of sugar-derived monomers and polymers. Chapter 2 describes direct modification of glucose to produce new sustainable and functional polymers. Glucose acrylate tetraacetate (GATA) was synthesized and shown to provide a useful glassy component for developing an innovative family of elastomeric and adhesive materials. A series of diblock and triblock copolymers of GATA and n-butyl acrylate (nBA) were created via RAFT polymerization. These block copolymers were investigated as thermoplastic elastomers (TPEs) and while the peel adhesion results were desirable, moderate mechanical properties were observed. As described in Chapter 3, further structural and chemical modifications were employed to improve the performance of these block copolymers. Isosorbide was also modified to prepare acetylated acrylic isosorbide (AAI), as another sugar-based glassy component. RAFT polymerization was employed to prepare ABA triblock copolymers of GATA and AAI with nBA. Comprehensive adhesion testings were conducted and adhesion properties comparable to many commercial pressure sensitive adhesives were observed. Additionally, GATA-derived triblock copolymers were chemically modified to promote self-complementary hydrogen bonding in their glassy domains, resulting in significant enhancement in their mechanical strength. The improvements observed in the properties of these materials as a result of such non-covalent interactions allows for improved design of sustainable, sugar-derived polymers as high performance TPEs. The second part focuses on controlled fabrication of cylindrical nanoparticles, described in Chapter 4. Block copolymers containing immiscible segments can self-assemble to generate ordered nanostructures, such as cylinders of one block in a matrix of the other in the bulk, which can then be sectioned on the nanoscale using a microtome (nanoskiving). Dispersing these sections in a selective solvent for the matrix block results in nanocylinders. In one example, we utilized a poly(N,N-dimethylacrylamide)-block-poly(styrene) (PDMA-PS) copolymer containing 36% by volume of PS. This composition was selected as it self-assembles into cylinders of PS in a matrix of PDMA. The cylinders were aligned using a channel die and the aligned samples were subsequently sectioned using a microtome. The resulting sections were dispersed in water, a selective solvent for the PDMA matrix, affording PS nanocylinders with a PDMA corona.
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    Renewable Aliphatic Polyester Block Polymer Thermoplastic Elastomers
    (2014-04) Martello, Mark
    The performance of thermoplastic elastomers is predicated on their ability to form mechanically tough physically crosslinked elastomeric networks at low temperatures and be able to flow at elevated temperatures. This dissertation focuses on renewable aliphatic polyester block polymers with amorphous polylactide (PLA) and their performance as TPEs. The goal of this work was to enhance the mechanical toughness of PLA containing TPEs; fundamental properties ranging from chemical composition and phase behavior, molecular architecture and melt processability, to melt polymerization strategies were investigated. ABA triblock polymers with PLA end-blocks and rubbery mid-blocks from substituted lactones comprised of poly(6-methyl-ε-caprolactone)(PMCL), poly(δ-decalactone), and poly(ε-decalactone)(PDL) were produced by sequential ring-opening polymerizations in the bulk. The bulk microstructure of symmetric PLA-PMCL-PLA and PLA-PDL-PLA triblock polymers formed long-range ordered morphologies and the interaction parameter of the repeat units was determined. High molar mass triblocks exhibited elastomeric behavior with good tensile strengths and high elongations. Small triblocks were coupled to produced (PLA-PDL-PLA)n multiblock polymers with high molar mass and accessible order-disorder transitions allowing for melt processing via injection molding. The mechanical toughness of the multiblocks was comparable to the high molar mass triblocks. The controlled polymerization of renewable δ-decalactone was accomplished with an organocatalyst at low temperatures in the bulk to maximize the equilibrium conversion of the monomer.