B. Orgasinska et al., Surface phenomena in discotic liquid crystals investigated using polarizedFTIR transmission spectroscopy, MAT SCI E C, 8-9, 1999, pp. 283-289
Influence of uncoated and spin-coated surfaces of four different substrates
on the bulk alignment of a discotic liquid crystal 2,3.6,7.10,11-hexapenty
loxytriphenylene (HPT) was investigated using polarized FTIR transmission s
pectroscopy. The substrates investigated are: Si, ZnS, ZnSe and CaF2. A pla
nar-heterogeneous alignment of HPT has been found on the uncoated surfaces
of Si and CaF2 substrates whereas HPT is planar-homogeneously aligned on si
milar surfaces of ZnS and ZnSe. In contrast, a homeotropic alignment of HPT
is observed on the surfaces of substrates of Si, CaF2 spin-coated by nylon
6/6. Under certain experimental conditions of temperature and time variati
ons, the anchoring transition from planar to homeotropic is observed for HP
T. The observed alignments of LC and the anchoring transition are explained
in terms of the topology and the interactions of the LC molecule with the
surfaces of the substrate and/or the polymer with which the substrate is sp
in-coated. (C) 1999 Elsevier Science S.A. All rights reserved.