The liquid crystal (LC) alignment capability in 4-n-pentyl-4′-cyanobiphenyl (5CB) on polyimide (PI) Langmuir-Blodgett (LB) surface with alkyl chain lengths was investigated. The pretilt angle of 5CB increased by unidirectional rubbing treatment on PI-LB surface. The induced optical retardation on PI-LB surface increased by the rubbing. The extrapolation length de of 5CB for rubbed PI-LB surfaces with even-number is small, compared with odd-number near the clearing temperature Tc. The extrapolation length de of 5CB with odd-number increases gradually as the temperature increases but it tends to diverge near the Tc. Therefore the polar anchoring strength with even-number is strong because of relatively high surface ordering caused by more crystalline surfaces. The anchoring energy of 5CB with alkyl chain length of 7 carbons is approximately 1 × 10-3 (J/m2); it indicates the strong anchoring strength. In consequences, we suggest that the LC align capability in NLC on PI-LB surface is strongly related to the characteristics of the polymer.
|Number of pages||10|
|Journal||Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals|
|Publication status||Published - 2000|
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics