Synthesis of Hyperbranched Polyisoprene by Isoprene/Dimethyl‐di‐2,4‐Pentadieneyl‐(E,E)‐Silane Copolymerization Catalyzed with Half‐Sandwich Scandium Complex

Abstract

A series of hyperbranched polyisoprenes (HBPIps) are synthesized by copolymerization of isoprene and a novel dipentadiene‐containing branching agent dimethyl‐di‐2,4‐pentadieneyl‐(E,E)‐silane (DMDPS) catalyzed by the half‐sandwich scandium complex (C5Me4SiMe3)Sc(CH2C6H4NMe2‐o)2/[Ph3C][B(C6F5)4]. Due to the high activity of DMDPS in copolymerization, and the very similar reactivity of the two pentadieneyl groups in DMDPS, the gelation reaction is successfully avoided in the highly branched products. The structural parameter branching factor (g′) of the HBPIps is determined to evaluate the branching degree. It is proved that in the polymerization both the concentration of DMDPS and isoprene exhibits significant influence on branching degree of HBPIps. By using the DMDPS as branching agent and simply controlling the polymerization conditions, high branching degree of g′ = 0.35 is achieved.