Convection-induced patterns in phase-separating polymeric fluids

The process of pattern formation and droplet coarsening has been studied for ternary polymeric fluids in which phase separation was induced by solvent evaporation. For a particular range of solvent evaporation rates and thicknesses of liquid layers, ordered hexagonal patterns were formed at the liquid film-air interface. We ascribe this effect to Benard-Marangoni convection induced by solvent evaporation and estimate conditions generating periodic two-phase structures in polymeric films. Droplet coarsening rate featured a crossover from R similar to t(0.89) to R similar to t(0.67) coinciding with the onset of convection and was explained by convection-induced stabilization of droplets against coalescence. [S0031-9007(98)07184-1].