Raman mapping of polymer dispersed liquid crystal

The electro-optical properties of polymer dispersed liquid crystals (PDLC) materials make them interesting for display applications, especially as light modulators through a controllable scattering effect. Their electro-optical performances are strongly correlated with the distribution of the liquid crystal director inside the droplets. We showed that the Raman spectrometry mapping allows to evidence the director distribution of liquid crystal molecules in a confined geometry. In this study, we have focused our attention to the case of nematic liquid crystal (5CB) droplets dispersed in a polymer matrix (PMMA). Considering the characteristic C=N polarized triple bond we have observed a change of the Raman spectrometry images by varying the orientation of the droplet axis versus to the pump beam polarization. To explain these changes, we purpose to use the classical bipolar droplet model. This ideal representation of the liquid crystal organisation inside the droplet enabled us to easily determine the general form of the Raman spectrometry maps. (c) 2004 Elsevier B.V. All rights reserved.