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, a 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 a turnover frequency (TOF) of 48 000 h⁻¹, this system exhibited the highest polymerization activity yet recorded for MMBL living polymerization.