Structure/property relationships in nematic liquid crystal/polymer alignment layer interactions

The interactions occurring at the interface between a liquid crystal (LC) a nd the walls of a LC cell have been studied using microsecond time resolved Fourier transform infrared (FTIR) spectroscopy. We have found that, by var ying the structure of the alignment layers, different rates of electro-opti cal response could be achieved. These differences stem from the different s trengths of interactions between the LC and the alignment layers. No specif ic, strong interactions (i.e. hydrogen bonding) were found by a direct anal ysis of the spectra. By calculating the local dipole moment of the polymer films using semi-empirical molecular orbital methods, a direct correlation between the electro-optical behavior and dipole moment was found for severa l polymers with similar base structures. This shows that the interactions a t the LC/alignment layer interface are dominated by dipole-dipole forces. ( C) 2000 Elsevier Science B.V. All rights reserved.