Self-assembly of condensation homopolymers: with application in fractionation

Abstract

Self-assembly constitutes a versatile and important pathway to the emergence of complexity. The conventional wisdom in the polymer regime typically focuses on the utility of either main chain–main chain block copolymers or main chain–side chain addition polymers. Herein, the self-assembly of a condensation homopolymer is reported, presenting a distinct alternative to the conventional regime. In particular, a unique inverse main chain–side chain amphiphilic polymer architecture has been designed into a squaramide condensation homopolymer, with a polar solvophilic main chain and a nonpolar solvophobic side chain. This architecture provides a hitherto elusive contrast to the currently dominant canonical amphiphilic polymer architecture for addition polymers, with a nonpolar solvophobic main chain and a polar solvophilic side chain. As such, the squaramide condensation homopolymer synthesized herein showcases intriguing self-assembly into primary micelle and compound micelle constructs in a solvent–nonsolvent medium, allowing for fractionation into varied chain length fractions, each with a narrow polydispersity. The superior efficiency and accuracy observed in the four-step sequential fractionation as well as one-step fractionation for five as-synthesized chain lengths and six degradation-engendered chain lengths indicate self-assembly fractionation to be a powerful mechanistic framework for the precise targeting of diverse polymer structures and functions.