Liquid crystal alignment property of n-alkylthiomethyl- or n-alkylsulfonylmethyl-substituted polystyrenes

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 degrees. 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/m(2), respectively. Copyright (C) 2009 John Wiley & Sons, Ltd.