Crystallization assisted microphase separation in all-conjugated phenylene-thiophene diblock copolymers

Abstract

We demonstrated the crystallization assisted microphase separation of all-conjugated diblock copolymers poly (2,5-dihexyloxy-p-phenylene)-block-(3-hexylthiophene) (PPP-b-P3HT, denoted as BmTn). The crystallization and microphase separation are summarized in terms of the difference of aggregation in solvent and the crystallization temperatures of two blocks, respectively. B39T18 and B41T44 were selected, and crystalline nanowires were formed for B39T18 cast from non-selective solvent via the crystallization of PPP block overwhelming P3HT block. However, both microphase separation and crystallization occurred from selective solvent for PPP block, due to the enhanced aggregation of P3HT block governed by solvophobic interactions. The morphological evolution of B41T44 with equivalent crystallization capacity displayed an opposite result. The lamellar nanostructures formed in films were cast from non-selective solvent and the crystallization breakout microphase separation was formed from selective solvent. Besides, the evolution and phase transition in the thermal annealing process indicated that the PPP crystallized confined from the molten in the P3HT crystalline region, and then the P3HT breakout crystallized primarily and microphase separation with the molten PPP occurred.