A new synthetic route to borane-terminated isotactic polypropylenes via styrene/hydrogen consecutive chain transfer reaction

This paper discusses a new process of preparing borane-terminated isotactic polypropylenes (i-PPs) via in situ chain transfer reaction, which avoids the use of B-H-containing chain transfer agent and thus can be carried out with Al-activated metallocene catalyst under mild reaction conditions. The chemistry centers on a consecutive chain transfer reaction, first to a trialkylborane-containing styrene derivative, 4-[B-(n-butylene)-9-BBN]styrene (B-styrene), then to hydrogen in the isoselective polymerization of propylene catalyzed by rac-Me ₂Si(2-Me-4-Ph-Ind) ₂ZrCl ₂/MAO. The borane-terminated i-PP thus obtained keeps the desired properties of a polymeric alkyl-9-BBN reagent and was used to initiate radical polymerization of methyl methacrylate (MMA) to prepare i-PP-b-PMMA diblock copolymer.