Studies of optical transmission properties of electron beam cured polymer/liquid crystal systems

✍ Scribed by Lahcène Méchernène; Leïla Benkhaled; Djamila Benaissa; Ulrich Maschke

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 634 KB
• Volume: 31
• Category: Article
• ISSN: 0925-3467
• DOI: 10.1016/j.optmat.2008.07.004

✦ Synopsis

Polymer dispersed liquid crystal (PDLC) films were obtained by a polymerization induced phase separation technique induced by electron beam (EB) curing. A binary system composed of a monomeric diacrylate and a nematic liquid crystal (LC) was employed as initial reactive blend prior to the polymerization/ cross-linking processes. The detailed experimental investigation of the electro-optical response was conducted for a set of PDLC films. The analysis was accomplished by a proper morphology consideration and refractive index measurements, which depend on the solubility of LC in the cured polymer matrix.

A known model describing the electro-optical response of PDLC films based on a minimization of the total electrical and elastic energy of the nematic LC droplets dispersed in the polymer matrix was applied to describe the obtained experimental results. This model is based on the assumption that the single scattering is implemented, the droplet structure is not altered by an application of the electrical field, and only the droplet director changes its orientation with the applied field. The electro-optical response of PDLC films was expressed via a hierarchy of order parameters. Experimental results of the refractive index measurements and the morphological and thermophysical investigations were used as input parameters to compare theoretical and experimental results. A good agreement between the experimental data and calculated transmittance/voltage dependencies was found, when the multiple scattering in the film is negligible.