NUMERICAL-SIMULATION OF THERMALLY-INDUCED PHASE-SEPARATION IN POLYMER-DISPERSED LIQUID-CRYSTALS

We have developed a model of polymer-dispersed liquid crystal (PDLC) f ormation by thermally induced phase separation. Spinodal decomposition in the thermoplastic-LC mixture is modelled by the cell dynamical sys tems method of Oono and Purl, suitably modified to describe a continuo us temperature quench. Numerical calculations performed on a two-dimen sional system for a composition of 30% LC + 70% thermoplastic reveal t hat the final morphology depends strongly on the quench rate: If cooli ng is much faster than phase separation, then complete decomposition i s precluded, whereas for slower quenches we recover the usual LC-rich droplet pattern of constant-temperature studies. The droplet size dist ributions are quite broad, and the mean droplet size at a given temper ature decreases as a power of the quench rate, consistently with what is observed in real PDLCs. (C) 1996 American Institute of Physics.