Synthesis and 1,3-butadiene polymerization behavior of cobalt complexes containing benzotriazole-substituted pyridine ligands

Abstract

A series of cobalt complexes contai-ning benzotriazole-substituted pyridine ligands were synthesized. The effects of the type of cocatalyst, substituent structure, and polymerization temperature and time on 1,3-butadiene polymerization were investigated. The results showed that after activation by methylaluminoxane, these complexes exhibited medium to high activities for 1,3-butadiene polyme-rization. The activity of the complex depended on the substituent at 2-position of pyridine on the ligand. An increment of the bulkiness of substituent resulted in a decrease in activity, but it was not significantly related to the cis-1,4- selectivity of the polymer. Among them, cobalt complex with hydrogen substituent group showed the highest activity and cis-1,4- selectivity, affording polybutadiene with predominant cis-1,4- unit mole fraction of 94.0%, a number average molecular weight of 124.8×103 g/mol, and a narrow molecualr weight distribution (polydispersity index 2.0). Raising the reaction temperature could significantly increase the polymerization rate, even at a high temperature of 80 ℃，the polymer yield remained up to 93.6%, implying the high thermal stability of the catalyst system.

Keywords

• benzotriazole， polybutadiene， cobalt based catalysts， substituent， polymerization ，temperature，