Observation of orientational ordering processes of 4- n-pentyl-4′-cyanobiphenyl molecules during evaporation onto polyimide Langmuir–Blodgett films by optical polarized absorption measurements

Abstract

Orientational ordering processes of 4- n-pentyl-4′-cyanobiphenyl (5CB) molecules were examined, in situ, using optical polarized absorption technique whilst 5CB molecules were evaporated onto synthetic silica substrates coated with n-layer Kapton-type polyimide Langmuir–Blodgett film ( n = 3, 5, 7, and 11). It was found that the second orientational order parameter S 2 of 5CBs deposited onto the 3-layer polyimide substrate is lower than S 2 of 5CB deposited onto the 5-, 7-, and 11-layer polyimide-coated substrates when the amount of the deposited LC molecules is 10 times as much as that of a single monolayer. The results were discussed in terms of anchoring phenomena.