Liquid crystal alignment properties of poly(styrenesulphonate)/alkyltrimethylammonium complexes

Abstract

We synthesised a series of poly(4-styrenesulphonate)/alkyltrimethylammonium (PSS-#Cx, # = 12, 14 and 16; x=80, 60, 40 and 20) complexes, where # is the number of carbon atoms in the alkyl groups in alkyltrimethylammonium bromide, and x is the molar content (%) of alkyltrimethylammonium moiety, 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 alkyl side group and a higher molar content of alkyl side group showed homeotropic LC alignment behaviour with a pretilt angle of about 90 degrees. The homeotropic LC alignment behaviour was well correlated with the surface energy of the polymer films. Homeotropic LC alignment was observed when the surface energy values of the polymer were smaller than about 44.87 mJ/m2.