"Core-first" approach for the synthesis of star-shaped polyisoprenes with a branched core and isoprene catalyzed by half-sandwich scandium complexes. Issue 36 (1st September 2021) - Yu, Jialin
Abstract : Star-shaped polyisoprenes were synthesized by copolymerization of isoprene and branched homopolymer of dimethyl-di-2, 4-pentadienyl-( E, E )-silane through "Core-first" approach catalyzed by half-sandwich scandium complex. Abstract : A series of star-shaped polyisoprenes (Star-PIps) were synthesized by copolymerization of isoprene as an arm monomer and a branched homopolymer of dimethyl-di-2, 4-pentadienyl-( E, E )-silane (DMDPS) as a macromonomer core through the "core-first" approach catalyzed by the half-sandwich scandium complex (C5 Me4 SiMe3 )Sc(CH2 C6 H4 NMe2 - o )2 /[Ph3 C][B(C6 F5 )4 ]. Due to the different activities of DMDPS in polymerization with two catalysts (C5 Me4 SiMe3 )Sc(CH2 C6 H4 NMe2 - o )2 (Sc-1) and (C5 H5 )Sc(CH2 C6 H4 NMe2 - o )2 (Sc-2), a series of macromonomers with varied molecular weights and numbers of pendant vinyl groups were successfully obtained. The different activities and reaction characteristics of DMDPS in the two catalytic systems were also verified in detail by computational chemistry. Star-PIps with different molecular weights from 26.2 × 10 3 to 175.8 × 10 3 g mol −1 and arm numbers from 19 to 70 were produced when different macromonomers were used as cores. By changing the concentration of isoprene, Star-PIps with varied arm lengths were achieved.