Publication Title

Physical Review E

Publication Date

9-15-1998

Document Type

Article

DOI

10.1103/PhysRevE.58.3295

Keywords

Nematic Liquid Crystals, Temperature Dependence, Anchoring Strength, Alignment, Energy, Photopolymers, Orientation, Interface, Light

Disciplines

Physics

Abstract

The mechanism of liquid crystal pretilt angle generation on photoreactive polymer films doubly exposed to linearly polarized ultraviolet (uv) light has been investigated. The first exposure for time; tau(1) is normal to the surface, and the film is subsequently irradiated for time tau(2) With obliquely incident uv light with a plane of polarization rotated by 90 degrees with respect to that of the first uv light. The state of the polymer film after two exposures was characterized with a tensor order parameter, which then served as a boundary condition for the surface state of the nematic liquid crystal. The bulk liquid crystal behavior was investigated using Landau-de Gennes theory extended to include the possibility for weak surface interactions linear in the tensor order parameter. The pretilt angle was calculated as a function of both tau(1) and tau(2), and as a function of the second uv light angle of incidence. The calculated behavior of the pretilt angle was found to be in qualitative agreement with experimental observations. Conclusions about the strength of the anchoring have also been made.

Comments

Copyright 1998 American Physical Society. Available on publisher's site at http://dx.doi.org/10.1103/PhysRevE.58.3295.


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