Cascade synthesis of architecture-transformable thermo-labile multisite multiblock copolymers

Abstract

Rational design of architecture-transformable polymers can gain insight into stimulus-structure–property correlations to optimize physicochemical properties. To achieve versatile topological transformations, a couplable and self-immolative ATRP initiator N,N-bis(2-(bromoisobutyryloxy)ethyl)-9-anthracenemethanamine is used for one-shot copolymerization of styrene with 2-maleimidyl-4-thiobutyrolactone. The cascade synthesis involving atom transfer radical polymerization, atom transfer radical coupling and organobase-catalyzed cleavage of ester groups can be classified into four stages, in which chain architectures consecutively transform from BAB-type triblock copolymer to (BAB)_n-type multisite multiblock copolymer (MMBP) and (A′B-co-BA′)_r-type copolymer with reduced block number and distinct connection mode. In addition to UV-induced intrachain anthracene dimerization to generate MMBPs with a single-chain folding backbone, the incorporation of thiolactone groups into MMBPs allows to construct multiblock graft copolymers containing poly(ethylene glycol), poly(ε-caprolactone) and poly(N-isoproylacrylamide) side chains by the combination of grafting onto and grafting from approaches. Upon heating, the quantitative cleavage of anthracene dimer and ester groups is liable to form mixtures of di-/triblock copolymers comprising linear and/or comblike blocks. Owing to tunable compositions and functions, MMBPs may serve as a promising platform to achieve a wide range of complex macromolecular architectures via topological transformation.