(732h) Thermodynamic Interactions and Tunable Properties of Thermoplastic Elastomers Derived from Vegetable Oils

Linear ABA triblock copolymers, such as poly(styrene-b-butadiene-b-styrene) and poly(styrene-b-isoprene-b-styrene), are among the most important and widely used thermoplastic elastomers (TPEs). However, those TPEs are derived from fossil fuels. Due to the finite availability of fossil fuels and the environmental impact of fossil fuels manufacturing, there has recently been an urgent need to develop alternative polymeric materials from sustainable sources. In this study, lauryl acrylate (LAc) and stearyl acrylate (SAc), derived from vegetable oils, were polymerized with reversible addition-fragmentation chain transfer polymerization, and subsequently extended for the preparation of poly(styrene-b-(LAc-co-SAc)-b-styrene) triblock copolymers. The thermal and mechanical properties of polyacrylate random copolymers were readily tuned by variation of the acrylate composition and resulting distribution of side-chain lengths. The order-disorder transition temperatures of the triblock copolymers were surprisingly independent of the mid-block composition, implying the Flory-Huggins interaction parameter is also independent of the acrylate side-chain length. Structural analysis revealed the non-equilibrium spherical morphologies of the triblock copolymers, which transformed to cylindrical microstructures under large amplitude oscillatory shear with the cylinders aligned transverse to the shear flow direction. Tensile testing experiments indicated that these triblock copolymers exhibit elastomeric behavior at room temperature.