Coating speed dependence of main chain orientation and aggregation of PBTTT-C16 in the bar-coated thin film

Homogeneous alignment of a π-conjugated polymer, poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C16), was obtained by the bar-coating method in thin film. The macroscopic direction of the main chain orientation, that tended to be parallel or perpendicular to the coating direction, strongly depended on the coating speed. The optical and electrical anisotropies of the bar-coated thin film were demonstrated. By observing the surface morphology, it is revealed that the coating speed affected the polymeric aggregation. The molecular orientation mechanism through the polymeric aggregation in the coating process was discussed.