Phase separation in two-dimensional binary fluid mixtures: spontaneous pinning effect.
The dynamics of phase separation, under asymmetric quench, is studied for binary mixtures by molecular dynamics simulations. We consider two kinds of systems, i.e., the small molecular liquid mixture and the flexible chain blend. The domain growth is found to be dependent crucially upon the relative composition of the mixture. For a near symmetric quench with volume fraction not far away from the critical value, we find that the domain growth is obviously slowed down (the spontaneous pinning effect) when the phase-separating structure undergoes the percolation-to-cluster transition. However, as the volume fraction of the minority phase is decreased, a pinning-depinning transition of the domain growth is observed for certain asymmetric quenches, due to the correlated motion of droplets. For sufficiently asymmetric quenches where the volume fraction of the minority phase is low, the domain growth is suppressed at late stages for the flexible polymer blend, in contrast to the fast growth for the small molecular system. The results are in good agreement with previous studies, and confirm the possibility of the intermittent or final pinning of phase separation for isolated droplets structure.
National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China.
Yan-Li
YL
Tang
Yu-Qiang
YQ
Ma