Physical Behavior of Triblock Copolymer Thermoplastic Elastomers Containing Sustainable Rosin-Derived Polymethacrylate End Blocks

A rosin-derived polymethacrylate, poly(dehydroabietic ethyl methacrylate) (PDAEMA), was evaluated as a sustainable end block in triblock copolymer-based thermoplastic elastomers. Triblock copolymers containing glassy PDAEMA end blocks and a rubbery poly(n-butyl acrylate) (PnBA) midblock were synthesized through atom transfer radical polymerization. The volume fraction of PDAEMA in the triblock copolymer was varied at constant midblock molecular weight. At lower PDAEMA content, the triblock copolymers exhibited microphase separated morphologies lacking long-range order, which transitioned to a well defined cylindrical morphology as the PDAEMA content was increased. Observed thermal properties were consistent with the presence of distinct PDAEMA and PnBA domains. The order-disorder transition temperature increased with increasing PDAEMA content in the block copolymer, and the Flory-Huggins interaction parameter of PDAEMA/PnBA was strongly temperature-dependent yet small in value. The triblock copolymers exhibited elastomeric behavior at room temperature and accessible order disorder transitions, appropriate for thermoplastic elastomer applications.