Development of Shape-Tunable Monodisperse Block Copolymer Particles through Particle Restructuring by Solvent Vapor Annealing

Uniformity and controllability of size, shape, and internal structure of block copolymer (BCP) particle are important to determine their functionality. Here, we introduce the particle restructuring by solvent engineering (PRSE) strategy to transform the size-controlled, monodisperse BCP spheres into non-spherical BCP particles with well-defined internal structure. PRSE process starts with generating monodisperse BCP spheres in a wide range of particle size using membrane emulsification. Then, successful shape transformation into non-spherical prolate and oblate was demonstrated while maintaining the monodispersity of particle size. PRSE can be applied generally to various functional BCPs including polystyrene-block-poly(1,4-butadiene) (PS-b-PB), polystyrene-block-polydimethylsiloxane (PS-b-PDMS), and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP). Therefore, it allows an effective control of aspect ratio (AR) of the particles over a wide range, which was supported by theoretical calculation describing particle elongation. Further investigation on transformation kinetics during the PRSE showed that the morphological transformation was driven by reorientation of BCP domains, and it was strongly associated with overall molecular weight of the BCP and the annealing time.