Formation and Transformation of Polystyrene-block-poly(2-vinylpyridine) Hexasomes in the Solvent Exchange

The generation of inverse micellar nanostructures, especially those with open channels, using commercially available diblock copolymers (BCP), is vital for their wide applications in drug delivery and catalyst templating. However, the rigid requirements for forming inverse morphologies, such as the highly asymmetric molecular structures, the semicrystalline motifs, and concentrated solutions of diblock copolymers, represent obstacles to the development of successful strategies. In this study, the inverse polystyrene-block-poly(2-vinylpyridine) (PS30K-b-P2VP8.5K) micelles, i.e., the hexasomes with p6mm lattice, were generated through a modified solvent exchange via adding D-tartaric acid (D-TA) in the nonsolvent. Various intermediate morphologies have been identified with the change of D-TA concentration. Interestingly, in the high D-TA concentration (similar to 20 mg/mL), the hexasomes with close-packed hoops changed to mesoporous spheres with regularly packed perpendicular cylindrical channels (VD-TA: VBCP 6:100), and further to the mesoporous spheres with gyri-like open pores (VD-TA: VBCP > 15:100) with the increasing acidity in the mixed solvent. This study presents a simple and economical pathway for fabricating PS30K-b-P2VP8.5K hexasomes and first demonstrates these hexasomes can be modified to the morphology with open channels that will benefit their further applications.

Automated summary

In this study, inverse micellar nanostructures with open channels were successfully generated using a modified solvent exchange method. The addition of D-tartaric acid induced the formation of mesoporous spheres with regularly packed perpendicular cylindrical channels and subsequently mesoporous spheres with gyri-like open pores. The findings provide a simple and economical pathway for fabricating hexasomes with open channels, which could be beneficial for their further applications.