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Alignment Properties (alignment + property)
Selected AbstractsInfluence of Side-Chain Structure and Irradiation Condition on Photoalignment of Ladder-Like Polysiloxane Films,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2005H.-W. Gu Abstract In this paper we consider the photo-induced aligning capability of various ladder-like polysiloxane-based photoalignment films,which could be used in liquid-crystal displays,bearing different photoreactive side chains, i.e., laterally grafted cinnamate/azobenzene-based dual photoreactive side chains with a short or longer spacer, and terminally fixed coumarin-containing side chains. Results from polarized optical microscopy (POM), Fourier-transform infrared (FTIR) spectroscopy, surface-enhanced Raman scattering (SERS), atomic force microscopy (AFM), etc., are integrated to elucidate the influence of side-chain structure and the irradiation conditions on the photoalignment of ladder-like polysiloxane films. It is demonstrated that the film containing the dual photoreactive group with a longer spacer exhibits better alignment properties. Reasonably, the concerted photoreactions of the dual photoreactive group and the longer spacer are beneficial to the cooperative motion of chromophores at the "domain level", resulting in improved alignment facility and stability. The complicated effects of irradiation conditions and moderate annealing are also discussed. High-quality alignment of the polysilsesquioxane (LPS)-based photoalignment film LPS-CA11 with a longer spacer between the LPS main chain and cinnamoyl/azobenzene side chains can be achieved only within an optimal range of exposure (5,8,J,cm,2), while the pretilt angles can be adjusted in the range 0.5°,7° by varying the incident light intensity. Additionally, moderate annealing before and after illumination can markedly improve the alignment uniformity by self-healing of defects. [source] 4-Alkylphenoxymethyl-Substituted Polystyrenes for Liquid Crystal Alignment LayersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2009Hyo Kang Abstract We synthesized a phenoxymethyl-substituted polystyrene (PHP) and a series of 4-alkylphenoxymethyl-substituted polystyrenes, where the alkyl group is (CH2)nH (n,=,1, 2, 4, 6, and 8), using polymer analogous reactions, in order to study the effect of the phenoxymethyl and 4-alkylphenoxymethyl side groups on the liquid crystal (LC) alignment properties. The LC cell fabricated with the rubbed PHP film exhibited homogeneous planar and perpendicular LC alignment with respect to the rubbing direction. On the contrary, the LC cells made from the 4-alkylphenoxymethyl-substituted polystyrenes showed homeotropic LC alignment behaviors even at a very high rubbing density of 250, regardless of the length of the alkyl groups. Previously, n -alkylsulfonylmethyl-substituted polystyrenes with alkyl groups having more than 8 carbons (n,>,8) showed homeotropic LC alignment behavior. Therefore, the additional phenoxy group in the side chain was found to improve the homeotropic LC aligning ability of the polystyrene derivatives. [source] Liquid crystal alignment property of n -alkylthiomethyl- or n -alkylsulfonylmethyl-substituted polystyrenesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2009Hyo Kang Abstract We synthesized a series of n -alkylthiomethyl-substituted polystyrenes (#T-PS, #,=,4, 8, 12, and 16) and n -alkylsulfonylmethyl-substituted polystyrenes (#S-PS, #,=,4, 8, 12, and 16), where # is the number of carbon atoms in the n -alkyl side group of the polymers, using polymer analogous reactions to investigate their liquid crystal (LC) alignment properties. In general, the LC cell fabricated using the polymer film having a longer n -alkyl side group, a thioether linkage group, and a higher molar content of n -alkyl side group showed homeotropic LC alignment behavior with a pretilt angle of about 90°. The homeotropic alignment behavior was well correlated with the surface energy of the polymer films; when the positive dielectric anisotropic LC (ZLI-5900-000 from Merck) and negative dielectric anisotropic LC (MLC-7026-000 from Merck) were used to fabricate the LC cells, homeotropic alignment was observed when the surface energy values of the polymer were smaller than about 25 and 32,mJ/m2, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||