Cylinder-to-gyroid phase transition in a rod-coil diblock copolymer

In this communication, the morphology of well-defined P3DDT-b-PMMA with a 65.2% PMMA coil volume fraction is revealed as a hexagonally packed cylinder structure by X-ray scattering experiments after thermal annealing. Upon heating, an order-to-order transition (OOT) between cylindrical and gyroidal structures is observed at temperatures above 170 degrees C. The evolution of the cylinder to the gyroid occurs while the crystalline structure of the P3DDT block disappears, suggesting the conformation of the P3DDT-b-PMMA at high temperatures is similar to coil-coil block copolymers. The phenomena reported here can provide a different viewpoint of the self-assembly behaviors of poly(3-alkylthiophene)-containing rod-coil block copolymers. The novel rare gyroid structure of this rod-coil copolymer is useful to fabricate long sought of bicontinuous structure for highly efficient polymer solar cells.