Rapid and Living Polymerization of Renewable Methylene Butyrolactones via Borane/Phosphine Lewis Pairs

Abstract

Living polymerization techniques are crucial for polymer synthesis and applications. However, developing living/controlled polymerization systems for renewable monomers remains challenging. This study presents a highly effective organic Lewis pair system, combining tris(pentafluorophenyl)borane (B(C6F5)3) with the strong organophosphorus superbase P(NIiPr)Ph2, enabling rapid and living polymerization of renewable methylene butyrolactones (α-methylene-γ-butyrolactone (MBL) and γ-methyl-α-methylene-γ-butyrolactone (MMBL)) in dichloromethane at room temperature. The living Lewis pair polymerization (LPP) system was evidenced by a linear correlation between polymer molecular weight and monomer conversion, consistently narrow distribution (Đ), successful chain extension, and the synthesis of well-defined random and diblock copolymers with low Đ values. DOSY, DSC, and GPC analyses confirmed the formation of a structurally defined PMMBL-b-PMBL diblock copolymer. With 48,000 h-1 turnover frequency (TOF), this system demonstrated the highest polymerization activity yet recorded for the MMBL living polymerization.