Sequentially bridging anionic addition and ring-opening polymerization by cooperative organocatalysis: well-defined block copolymers from methacrylates and cyclic esters

Abstract

The organocatalytic sequential block copolymerization of dissimilar monomers with distinct chemical characteristics is very challenging, usually involving the integration of different polymerization mechanisms. In this contribution, we report the synthesis of well-defined block copolymers via sequential anionic addition polymerization of methacrylates and ring-opening polymerization (ROP) of cyclic esters using cooperative organocatalysis. The potential organocatalysts were first optimized for the two individual polymerizations: namely, addition polymerization of methacrylates and ring-opening polymerization (ROP) of cyclic esters. Subsequently, the poly(methacrylate-block-esters) were synthesized with the optimal t-BuP₄/isopropyl thiourea via sequential monomer addition, based on the living/controlled features in each polymerization cycle. t-BuP₄/isopropyl thiourea exhibited broad monomer adaptability and allowed the fabrication of structurally diverse block polymers. The block copolymers were stringently confirmed by gel permeation chromatography (GPC), ¹H and ¹³C NMR, diffusion ordered NMR spectroscopy (DOSY), and differential scanning calorimetry (DSC). Accordingly, a green and straightforward approach to preparing well-defined and diversified block polymers from different types of monomers was developed for the first time.