Stereoselective copolymerization of 4-(N,N-diphenylamino)styrene and isoprene by a C5H5-ligated scandium catalyst: synthesis of amino-functionalized crystalline styrenic thermoplastic elastomers

Abstract

The copolymerization of 4-(N,N-diphenylamino)styrene (DPAS) with isoprene (IP) as catalyzed by the half-sandwich scandium compound (C₅H₅)Sc(CH₂C₆H₄NMe₂-o)₂ has afforded a new class of amino-functionalized crystalline styrenic thermoplastic elastomers. The homopolymerization of DPAS bearing a sterically demanding diphenylamino group took place in a quasi-living fashion, yielding the amino-functionalized syndiotactic polystyrene by using this scandium catalyst. In the copolymerization of DPAS with IP, the DPAS units started to become incorporated into the polymer chains after IP was almost completely consumed, yielding the diblock copolymers containing a syndiotactic poly(DPAS) block and a cis-1,4-poly(IP) block with controllable block lengths. Addition of a mixture of DPAS and IP to a completed DPAS polymerization reaction mixture in one pot afforded the DPAS–IP–DPAS triblock copolymers with controllable block lengths. The DPAS–IP–DPAS triblock copolymers showed glass transition temperatures (T_g values of −62 °C and 120 °C) and a melting point (T_m value of 219 °C) originating from the cis-1,4-poly(IP) block and syndiotactic poly(DPAS) blocks, respectively.