Powerful Ring-Closure Method for Preparing Varied Cyclic Polymers

Abstract

A powerful ring-closure method was developed for the formation of cyclic polymers by combining reversible addition–fragmentation chain transfer polymerization (RAFT) and light-induced Diels–Alder click reaction. The outstanding features of this novel method were demonstrated from the following four aspects. This convenient and efficient technique could produce cyclic polymers in air at room temperature without any other catalyst or stimulus requirements other than a mild UV irradiation. The universality of this method was demonstrated by successfully producing five different types of cyclic homopolymers including polystyrene, poly(methyl methacrylate), poly(tert-butyl acrylate), poly(N,N-dimethylacrylamide), and poly(2-vinylpyridine) and two kinds of block copolymers of poly(methyl methacrylate)-block-polystyrene and poly(methyl methacrylate)-block-poly(tert-butyl acrylate). This is the first time to report a one-pot ring-closure method for the formation of cyclic polymers, in which the crude monomer polymerization solution was directly diluted as precursors and no more requirements were needed to purify and postfunctionalize the linear polymer intermediates. When combing with a batchwise operation, this novel light-induced ring-closure method could significantly improve the notorious disadvantage of low cyclic polymer yield accompanied by the ring-closure strategy.