Numerical simulation of thermally induced phase separation in polymer-dispersed liquid crystals

We have developed a model of polymer-dispersed liquid crystal (PDLC) formation by thermally induced phase separation. Spinodal decomposition in the thermoplastic-LC mixture is modelled by the cell dynamical systems method of Oono and Puri, suitably modified to describe a continuous temperature quench. Numerical calculations performed on a two-dimensional system for a composition of 30% LC +70% thermoplastic reveal that the final morphology depends strongly on the quench rate: If cooling is much faster than phase separation, then complete decomposition is precluded, whereas for slower quenches we recover the usual LC-rich droplet pattern of constant-temperature studies. The droplet size distributions are quite broad, and the mean droplet size at a given temperature decreases as a power of the quench rate, consistently with what is observed in real PDLCs.