Comparison of the Photoinduced
Orientation Structure
in the Bulk and at the Near-Surface of a Photoalignable Liquid Crystalline
Polymer Film
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Abstract
The
thermally stimulated photoinduced in-plane and out-of-plane
molecular reorientation behaviors of a polymethacrylate film comprised
of 4-methoxycinnnamoylbiphenyl (MCB) side groups connected with a
decylene spacer (PMCB10M) are compared in the bulk (>10 nm), at
the
inner-surface (∼10 nm), and at the near-surface (<2 nm)
using polarized UV absorption and near-edge X-ray absorption fine
structure (NEXAFS) spectroscopies. The biaxial reorientation characteristics
in the bulk of the PMCB10 M films can be controlled by irradiating
with linearly polarized (LP) UV light and subsequent annealing to
generate self-organization of the MCB side groups. However, the homogeneous
in-plane orientation at the near-surface, which can introduce homogeneous
nematic low-molecular-weight liquid crystal mixture alignment, is
observed regardless of the self-organization process. The differences
in the orientation characteristics arise from long alkylene spacer
and bulky mesogenic side groups