Polymerization-induced self-assembly enables access to diverse highly ordered structures through kinetic and thermodynamic pathways

Abstract

Polymerization-induced self-assembly (PISA) has emerged as a powerful technique for generating microphase-separated structures, but research has primarily focused on systems exhibiting “disordered” structures. Here, we demonstrate the facile construction of various highly ordered microphase-separated structures via PISA, with and without kinetic control through manipulation of the glass transition temperature (T_g) of the core-forming blocks. We synthesized diblock copolymers in an ionic liquid (40 wt% solute) by polymerizing styrene or 2-hydroxyethyl acrylate from one end of poly(ethylene glycol). When using polystyrene as the core-forming block, its high T_g relative to the polymerization temperature resulted in the formation of kinetically trapped structures, including pure hexagonal close-packed (HCP) spheres exhibiting X-ray diffraction peaks up to the 17th-order. Conversely, lower-T_g core-forming block [poly(2-hydroxyethyl acrylate)] led to thermodynamically stable, highly ordered structures, including a double-gyroid morphology. These results highlight the efficacy of PISA for generating diverse, highly ordered microphase-separated structures from simple diblock copolymers and demonstrate its potential to access structures unattainable through conventional ex situ polymerization.