Transparent thermoplastic elastomers by anionic polymerization based on a soft polymethacrylate-segment and coupling strategies

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ABSTRACT: Living anionic polymerization was used to prepare well-defined polystyrene- b -poly( iso -decyl methacrylate) (PS- b -P i DMA) block copolymers (BCP), which were subsequently coupled with 1,4-butanediol dimethacrylate (BDDMA) to generate star-like branched architectures. The BCPs showed narrow molar mass distributions ranging from 1.04 to 1.05, with overall BCP lengths of 56,800 to 60,300 g mol -1 . It is shown that the convenient addition of the bifunctional methacrylate influenced the morphology compared to their linear BCP analogs. Thorough characterization by SEC with copolymer module analysis setup, 1 H-NMR spectroscopy, DSC, TGA, TEM, and SAXS confirmed controlled synthesis, successful linking strategies of the living BCP chain end, and emergence of microphase-separated morphologies in the bulk state. Depending on the composition, the materials formed lamellar or cylindrical nanostructures. Coupling led to domain shrinkage, while preserving ordered microphase separation. The resulting methacrylate-based thermoplastic elastomers combined high optical clarity with good processability. The resulting mechanical and optical properties were compared with those of industrially processed samples based on linear styrene-butadiene and styrene-isoprene TPEs. These results show that combining anionic polymerization with coupling chemistry is an effective route to transparent, processable thermoplastic elastomers with tunable nanoscale morphology. The herein-reported synthesis strategy paves the way to UV- and oxygen-stable TPEs compared to their butadiene-based BCP analogs.

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