Stereoblock polymerization of dienes in switching stereoselectivity by addition of MMAO cocatalyst

Hard-soft polydienes copolymers were synthesized by one-pot sequential polymerization with neodymium-based catalyst. trans-1,4 polybutadiene (TPB) was firstly obtained by the coordinative chain transfer polymerization (CCTP) of 1,3-butadiene (BD) with Nd(Oi-Pr)3/Mg(n-Bu)2 catalyst. Diblock copolymers with crystallizable TPB segment and soft cis-1,4 specific polydienes were achieved by sequential addition of BD/isoprene (IP) and MMAO to the polymerzaition system. The length of each block and microstructure of the copolymer are controllable by adjusting monomer feed ratio. The copolymer exhibits both glass transition temperature (Tg) originating from the soft blocks and melting point (Tm) originating from hard blocks of TPB, respectively. Moreover, the incorporation of TPB segment to the cis-1,4-PB could improved the mechanical properties of cis-1,4-PB and the cold-flow phenomenon was relieved.