Liquid crystal alignment behavior and OTFT performance of poly(3-hexylthiophene) blends with comb-like poly(oxyethylene)

Abstract

Alignment characteristics of nematic liquid crystal (LC) on the surface of conjugated semi-conducting polymer blends with a comb-like polymer were studied. Conoscopic polarized optical microscope images show vertical alignment of LC on the blend films regardless of blend ratio. The LC alignment behavior on the blended film surface can be explained by a preponderance of comb-like polymers at the film surface. The mobility values of organic thin film transistors (OTFT) prepared with the blend film as an active layer are found to be similar to those with a pure conjugated semi-conducting polymer film. This result suggests a novel route for effectively reducing the amount of active semi-conducting polymer without significant deterioration of charge carrier mobility in an OTFT device. Since the LC alignment can be controlled on the surface of channel layer of OTFT by employing the polymer blend as the semi-conducting layer, the LC alignment and OTFT performance with the blend composition can be investigated simultaneously.