Effect of 4-vinylpyridine incorporation on the shape transformation of poly(ethylene glycol)-block-polystyrene polymersomes

Abstract

The self-assembly of block copolymers enables the formation of diverse nanostructures, among which polymeric vesicles (polymersomes) are particularly significant. Poly(ethylene glycol)-block-polystyrene (PEG-PS) copolymers are known to self-assemble into polymersomes that can further undergo a shape transformation into bowl-shaped stomatocytes, a morphology that has been extensively studied. In this work, we investigate the incorporation of 4-vinylpyridine (4VP) into the hydrophobic domain of PEG-PS copolymers to introduce membrane functionality and broaden stomatocyte applications. We systematically examined the influence of 4VP content and polymer architecture on stomatocyte formation. Stomatocyte morphology was characterized qualitatively by electron microscopy and quantitatively by asymmetric flow field-flow fractionation (AF4) coupled with multi-angle light scattering (MALS) and quasi-elastic light scattering (QELS) detectors (AF4-MALS-QELS) using the shape factor (Rg/Rh). Our findings reveal that the presence of 4VP generally significantly affected stomatocyte formation, leading to reduced stomatocyte populations compared to the PEG-PS system. This required a thorough optimization of both polymer composition and shape transformation conditions to achieve optimal stomatocyte formation, demonstrating that even subtle variations in the hydrophobic domain can profoundly influence the resulting morphology.