Block Copolymers for Sustainable Thermoplastic Elastomers and Nanoparticle Fabrication

Abstract

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.