Self-Assembled Graft Copolymer Nanofibers with an Adjustable Internal and External Structure

Abstract

The nanofibers with designed internal and external morphology are of great interest for tissue engineering, regenerative medicine, and novel materials design. In this letter, we report on a possible mechanism for creating and tuning nanofibers from amphiphilic graft copolymers. The aggregation process in these polymers is governed not only by surface to bulk energy tradeoff but also by orientational entropy of pendants, which leads to the emergence of specific interactions in such systems known as orientation-induced attraction. Due to the orientation-induced attraction, the semiflexible amphiphilic graft copolymers can assemble into various fibrillar structures and undergo a non-obvious series of transitions upon changing solvent quality for pendants. The fibrils formed in a poor solvent, when the quality of the solvent is improved, first self-assemble into fibers and only then dissolve. Fibers are bundles of fibrils interconnected by jumpers from pendants. Their internal structure can be tuned by solvent quality and graft copolymer structure. Using a mesoscopic simulation approach, we revealed the conditions for these self-assembly processes to be realized and resolved inner and external morphology of each stage depending on the selective solvent quality and grafting density of pendants.