Synthesis of high cis-1,4 polybutadiene with narrow molecular weight distribution via a neodymium-based binary catalyst

Abstract

This work explores the synthesis of polybutadiene (PB) with high cis-1,4 unit content and narrow molecular weight distribution using a neodymium-based complex, consisting of neodymium(III) trifluoromethane sulfonate (Nd(CF₃SO₃)₃) and coordinated with tris(2-ethylhexyl)phosphate (TOP). The complex's composition and structure are characterized by elemental analysis, XPS and FT-IR. Combined with Al(i-Bu)₃, a binary catalyst is obtained and then applied to initiate the polymerization of butadiene. Results indicate that the catalyst system displays a high catalyst activity and the product polymer (PB) features a high cis-1,4 content (98.8%) and a remarkably narrow molecular weight distribution (M_w/M_n = 1.32). Compared with PB initiated by the current well-studied catalyst Nd(CF₃SO₃)₃*3TBP/Al(i-Bu)₃, the Nd(CF₃SO₃)₃*3TOP allows significantly narrowing the molecular weight distribution of the PB, because the Nd(CF₃SO₃)₃*3TOP is more easily dissolved in hexane. Therefore, butadiene was polymerized in a homogenous system and each monomer's polymerization was initiated in the single molecular state.