Influence of alkylene spacer length on photoinduced orientation of liquid crystalline polymer with N-benzylideneaniline side groups

ABSTRACT

Liquid crystalline polymers (LCPs) comprised of N-benzylideneaniline (NBA) side groups with different alkylene spacer length (n = 2, 6, and 10) are synthesized and their photoinduced reorientation behavior is investigated. Photoinduced orientation of NBA side groups is observed for all LCP films when exposing to LP-365 nm light, but the out-of-plane motion is simultaneously generated. When the polarization of LP-365 nm light is changed, in-plane optical anisotropy is reversibly changed and the out-of-plane motion is restricted for a P1 (n = 2) film. In contrast, reversibility of the photoinduced in-plane orientation is not effective for P2 (n = 6) and P3 (n = 10) films, where out-of-plane motion of the mesogenic NBA side groups is generated when the total exposure energy increases.

KEYWORDS:

• Polymer liquid crystal
• N-benzylideneaniline
• photoinduced orientation
• alkylene spacer
• reversible orientation