ORIENTATION DYNAMICS OF SIDE-CHAIN POLYMERS SUBJECT TO ELECTRIC-FIELDS .1. STEADY-STATE

Many polymeric glasses must be orientationally ordered for the materials to exhibit useful characteristics. The objective of this work was to understand the dynamics of the orientation and relaxation processes and to relate these behaviours to the structural characteristics of the polymeric material. In this study we considered materials suitable for nonlinear optical applications. In particular, thin polymer films, either doped with nonlinear optical chromophores or films with the chromophores covalently bonded to side groups were studied. Orientation of these chromophores was achieved by the application of an external electric field. Ellipsometry was used to measure the birefringence resulting from chromophore orientation and the steady state and transient behaviours were studied. Materials characteristics studied included method of chromophore incorporation, chromophore concentration, spacer length, and molecular weight. Our results showed that the polymer structure, specifically the tacticity, was the dominant factor determining the steady state and transient behaviours. The relationship between monomer and polymer structure and the resulting effect on the orientation dynamics is discussed. Qualitative agreement with theoretical predictions was obtained for the simpler guest/host system, but the model was shown to be inadequate to explain the behaviours of the more complex systems studied. The results reported here have provided valuable insight into the molecular processes that occur during the chromophore orientation and relaxation, and the effects of structural characteristics of the polymers on these mechanisms.