Facile topological transformation of ABA triblock copolymers into multisite, single-chain-folding and branched multiblock copolymers via sequential click coupling and anthracene chemistry

Architecture-transformable polymers with rational rearrangement of the chain structure may reshape the future of smart materials. Although the transition from block to multisegmented block copolymers is well documented, further transformation into high-order architectures has been scarcely revealed. This research aims at reaction-induced sequential transitions from ABA triblock copolymers (TBPs) to multisite (MMPs), single-chain-folding (SMPs) and branched (BMPs) multiblock copolymers. Consecutive ATRP and azidation afford α,ω-azido-mid-anthryl-functionalized ABA (A = poly(tert-butyl acrylate), B = polystyrene) copolymers, the double-strain-promoted azide−alkyne cycloaddition reaction gives (ABA)n-type MMPs, and UV-induced dimerization of pendant anthryl groups is adopted to generate SMPs or BMPs. The utilization of the self-accelerating click reaction and anthracene chemistry allows efficient construction of the desired polymers in a few hours, affording a robust platform for fast formation and transformation of MMPs. Fractional precipitation endows MMPs with relatively low dispersity and weight-average polymerization degree of ABA (nw) up to 72. With the formation of a more compact structure, the single-chain folding is prone to result in reduced apparent molar mass relying on dispersity and nw as well as decreased solution viscosity. The success of this study paves the way for on-demand transformation and tunable properties of multisegmented macromolecular architectures.