Neodymium-based one-precatalyst/dual-cocatalyst system for chain shuttling polymerization to access cis-1,4/trans-1,4 multiblock polybutadienes

Abstract

A new chain shuttling polymerization system was developed that utilizes only one neodymium precatalyst and two different types of cocatalysts to prepare cis-1,4/trans-1,4 stereo multiblock polybutadienes. This study provides a new alternative to achieve conjugated diene chain shuttling polymerization. For the butadiene polymerization with Nd(Oi-Pr)3/MMAO/Mg(n-Bu)2 system, a gradual reduction of the Mn of the resultant polymer with Mg(n-Bu)2 content increased while retaining narrow molecular weight distributions and unimodal GPC profiles, which indicated the occurrence of fast and reversible chain transfer. The trans-1,4 content increased from 7.7 % to 50.6 % with Mg(n-Bu)2 content increased, Mg(n-Bu)2 both served as cocatalyst to generate trans-1,4 regulating species and as chain transfer agent capable of shuttling the formed polymer chains between the two active species. Furthermore, the number-average degree of polymerization of the trans and cis blocks can be calculated from 13C NMR analysis. Differential scanning calorimetry and dynamic mechanical analysis was also performed to further validate the cis-1,4/trans-1,4 multiblock structure.