Study of Solution Assembly Behaviors of Regioregularity Controlled P3HT-P2VP Block Copolymers

In selective solvents, poly(3-hexylthiophene) (P3HT)-based block copolymers (BCPs) assembles into crystallized nanowire (NW) structures in contrast to micelluar (MC) structures from conventional coil-coil BCP. Herein, we demonstrate a transition of NW to MC structures of P3HT-based BCPs as changing of their regioregularity (RR) and thus their crystallinity. We synthesized a series of P3HT-b-P2VP copolymers, of which RR was systemically regulated from 95 to 55% and investigated their solution behavior in binary solvent mixtures. As expected, the well-defined NW structure was produced from the P3HT-b-P2VP with high RR of 95%. Between 80% and 65% of RR, intermediate morphologies between NWs and MCs were observed. When RR decreased, the widths and heights of such quasi-NWs measured by TEM and AFM, respectively, were gradually increased in reverse proportion to reduction of crystallinity analyzed by GIWAXS and DSC measurement. Under 65% of RR, crystallization of the P3HT moiety is sufficiently suppressed so that only MC structures were formed. Therefore, we demonstrate that nanostructures from amorphous MC to crystalline NW can be tailored by RR of the P3HT in solution assembly behaviors.