Application of time-resolved spectroellipsometry to the study of liquid crystal reorientation dynamics

Polarization modulated spectroellipsometry (PMSE), with a 1-ms time resolution and 0.01 degrees phase difference angular sensitivity, was used to study the dynamics of the electric field-induced homogeneous-homeotropic transition of nematic liquid crystals. Reflection PMSE carried out for a dye-doped liquid crystal cell can isolate the signals from molecules in the vicinity of substrate walls. Information about bulk molecules is obtained from transmission PMSE experiments. The transition of interface molecules is fast in both rise and decay processes (3 ms). The rise of bulk molecules is similarly fast, but the decay is slow (100 ms). The fast reorientation exhibited by interface molecules indicates the presence of a strong anchoring effect imposed by the substrate surface. (C) 1998 Elsevier Science S.A.