Modelling of the formation of non-uniform polymer networks in devices

Polymer Stabilised Liquid Crystal (PSLC) devices contain a polymer network (PN) formed from a liquid crystal host containing a low concentration of reactive liquid crystalline monomers. If a strongly UV absorbing liquid crystal is used, the UV intensity profile during polymerisation creates a nonuniformity in the polymerisation process and the final polymer distribution across the cell [1]. A theoretical model of the polymerisation process of the reactive mesogen molecules is presented which takes into account the UV intensity profile, the rate of polymerisation and molecular diffusion. The PN distribution has been calculated using realistic reaction parameters, diffusion constants and UV absorption coefficients for both a UV absorbing (E7) and a non-absorbing (ML1001) liquid crystal. SEM observations and optical microscopy were carried out and are found to support the numerical predictions.