Facile Synthesis of Tailor-Made Oiefin Block Copolymers Using ansa-Fluorenylamidodimethyltitanium Complex

摘要

@@We have previously reported that [t-BuNSiMe2(3,6-t-Bu2Flu)]TiMe2 (1)combined with trialkylaluminum-free MMAO (dMMAO) conducted living homopolymerization of propylene and norbomene as well as their random copolymerization with high activities. The catalytic system gave novel block copolymers eonsisted of syndiotactic polypropylene (PP) and poly(propylene-ran-norbornene) sequences. The melting point and the glass transition temperature of the block copolymer derived from the PP sequence and the copolymer sequence were controllable in a wide range by polymerization temperature and comonomer composition, respectively. We investigated the solvent effects on the syndiospecific living polymerization of propylene and found that the syndiospecificity was controlled by the polarity of the solvent. This result was applied for the synthesis of syndiotactic-atactic stereoblock PP by sequential addition of monomer and polar solvent used.This method is useful for the synthesis of di-stereoblock PPs but cannot be applied for the synthesis of multiblock PP, because the change of the stereospecificity is irreversible after the addition of polar solvent. In this study, we introduce novel synthetic procedure for the synthesis of tailor-made multiblock syndiotactic-atactic stereoblock PPs with a living stereo-controllable polymerization of propylene using the 1-dMMAO system, where propylene pressure was just changed during the living polymerization.