Thermally Induced Phase Separation of a Liquid Crystal in a Polymer under Microgravity: Comparison with Simulations

Abstract

The influence of cooling rate on the size and uniformity of liquid crystal droplets dispersed in a polymer matrix by a thermally induced phase separation (TIPS) process is investigated under a microgravity environment. The experimental results are compared with Monte Carlo simulations. Even though the simulations are carried out on a two-dimensional lattice, the results are in reasonably good agreement with the experiments. We find that a fast cooling rate gives smaller droplet sizes and hence a more uniform distribution as compared to the ones produced under a slow cooling rate. The formation of droplets under a fast cooling rate is similar to the simulated annealing process. For a fast cooling rate the system is unable to attain the global minimum and stays in a higher surface energy state which is associated with smaller droplets. For a given cooling rate, the effect of quench depth is studied by varying the final temperature. Simulation results show that at a shallow quench depth (high final temperature) a fast cooling rate is not effective in controlling the droplet morphology due to the high thermal energy possessed by the particles.