Sequence-Controlled Methacrylic Multiblock Copolymers: Expanding the Scope of Sulfur-Free RAFT

Abstract

Sulfur-free reversible addition–fragmentation transfer polymerization (SF-RAFT) in emulsion allows access to the synthesis of sequence-controlled methacrylic multiblock copolymers. Herein, we expand the scope of SF-RAFT emulsion polymerization by utilizing four different macrochain transfer agents (mCTA) to mediate the synthesis of diblocks and sequence-controlled methacrylic multiblock copolymers. Poly(methyl methacrylate) (pMMA), poly(butyl methacrylate) (pBMA), poly(ethyl methacrylate) (pEMA), and poly(benzyl methacrylate) (pBzMA) of a similar Mn (∼4300 g mol–1) were successfully synthesized via catalytic chain transfer polymerization (CCTP) in emulsion. The capability of these mCTAs to act as macroinitiators was investigated through the synthesis of “in situ” diblock copolymers and was then expanded to the synthesis of deca- and hexablock multiblock copolymers with varying degrees of polymerization (DPn = 10–50 per block, Mn,total = 7000–55 000 g mol–1), yielding well-defined copolymers with controlled molecular weights, quantitative conversions (>99%), and low dispersities (Đ ∼ 1.2) without employing sulfur or transition metal reagents.