Computational simulation of polymerization-induced phase separation under a temperature gradient

Abstract

Polymerization-induced phase separation (PIPS) via spinodal decomposition (SD) under a temperature gradient for the case of a monomer polymerizing in the presence of a non-reactive polymer is studied using high performance computational methods. An initial polymer (A)/monomer (B) one-phase mixture, which has an upper critical solution temperature (UCST) and is maintained under a temperature gradient, phase-separates and evolves to form spatially inhomogeneous microstructures. The space-dependence of the phase-separated structures under the temperature gradient field is determined and characterized using quantitative visualization methods. It is found that a droplet-type phase-separated structure is formed in the high-temperature region, corresponding to the intermediate stage of SD. On the other hand, lamella or interconnected cylinder type of phase-separated structure is observed in the low-temperature region, corresponding to the early stage of SD structure, in the large or small temperature gradient field, respectively. The kinetics of the morphological evolution depends on the magnitude of the temperature gradient field. The non-uniform morphology induced by the temperature gradient is characterized using novel morphological techniques, such as the intensity and scale of segregation. It is found that significant non-uniform structures are formed in a temperature gradient in contrast to the uniform morphology formed under constant temperature.