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Polymethacrylates with benzylidenephthalimidine side chains, 2. Photocontrol of alignment of a nematic liquid crystal
Author(s) -
Suh DongHae,
Ichimura Kunihiro,
Kudo Kazuaki
Publication year - 1998
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19980301)199:3<375::aid-macp375>3.0.co;2-#
Subject(s) - photoisomerization , liquid crystal , photostationary state , irradiation , side chain , photochemistry , azo compound , polymer , materials science , chemistry , photochromism , azobenzene , thermal stability , perpendicular , optoelectronics , organic chemistry , physics , geometry , isomerization , mathematics , nuclear physics , catalysis
The in‐plane alignment photocontrol of a nematic liquid crystal (LC) was performed by irradiation of thin films of polymethacrylates with benzylidenephthalimidine (BPI) side chains with linearly polarized UV light. The orientational direction of LC molecules was perpendicular to the electric vector of polarized actinic light and in line with that of BPI moieties in polymer films which were exposed to linearly polarized UV light. Prolonged polarized‐light‐irradiation leading to sufficient photodimerization did not result in the generation of a homogeneous alignment indicating unequivocally that the photoalignment is caused specifically by polarized‐light‐induced E/Z photoisomerization. The level of the photoinduced LC alignment was improved by p ‐methoxyl substitution at the benzylidene residue and by an appropriate choice of an irradiation wavelength giving Z ‐isomer as a predominant component at a photostationary state. Both effects are interpreted in terms of the molecular shape of BPI favorable for the generation of LC photoalignment. Photodimerization under controlled polarized‐light‐irradiation conditions enhanced considerably the thermal stability of LC photoalignment owing to the formation of crosslinks.