A unique fabrication strategy of hierarchical morphologies: combination of multi-step self-assembling and morphology transition

Abstract

Multi-compartmental cylindrical microstructures with lots of nanotubes on their surface, whose shape resembles a sea cucumber, have been fabricated for the first time. This hierarchical morphology is formed through transitions of vesicles to large compound vesicles, to sea cucumber-like hierarchical microstructures. Along with the morphology transitions, aggregation of the residual polymer chains in the solution occurs, which is called multi-step self-assembling. The driving force of the phase transitions and the multistep self-assembling is polymerization because with the progress of the polymerization, the chain length ratio of PS to P4VP increases, which induces self-assembling and morphology transitions. The requisite for multi-step self-assembling is a high concentration of the P4VP-PS chains remaining in the solution after formation of the nascent assemblies. The concentration of the residual block chains can be controlled by varying the recipe and content of the ethanol. Thus, this study provides a unique strategy to fabricate useful hierarchical assemblies.