Phase behaviour of mixtures of side‐chain LC polyoxetanes with E7 and their field response

Abstract

We prepared and characterized a series of side‐chain liquid crystalline (LC) homo‐ and copolyoxetanes containing varying fractions of the mesogenic 4‐decyloxy‐4′‐cyanobiphenyl pendent and the non‐mesogenic propoxy group. The miscibility of homo‐ and copolyoxetanes (Co‐LCPs) with E7 also was studied. The LC properties of the Co‐LCP/E7 mixtures were unique in that, although E7 is a nematic mixture, all the Co‐LCP/E7 mixtures form layered smectic mesophases. Among the mixtures, the composition of 30 wt % of LCP bearing 16 mol. % of the mesogenic pendant, Co(16)‐LCP, and 70 wt % of E7 formed the smectic phase over a broad range of temperature (−70 to 35°C), although the isotropization temperature of Co(16)‐LCP itself was below room temperature. A flexible plastic display was constructed utilizing this mixture and its display characteristics were evaluated. For a device with a 10 µm thick active layer, the threshold voltage was about 30 V and exhibited a rising response time of 200 ms. The most remarkable observation made was that the blends revealed excellent memory behaviour.

Acknowledgements

The X‐ray experiments at PLS were supported by the Ministry of Science and Technology and Pohang Steel Company. Other experiments were performed in the Center for Electro‐ and Photo‐responsive Molecules, Korea University, supported by the Korea Science and Engineering Foundation. Kyu‐Nam Kim and Young‐Wan Kwon are recipients of the BK21 fellowship from the Ministry of Education and Human Resources of the Republic of Korea. This research in part was supported by the Sudang Foundation, Seoul, Korea.