Effects of gelation on morphology of spinodal decomposition and viscous fingering

Abstract

We have studied the kinetics of spinodal decomposition in a gelatin—water—methanol mixture which undergoes a sol—gel transition simultaneously with phase separation, using light scattering and video-microscopy techniques. We found that the kinetics of phase separation depends very strongly on temperature; and for deep quenches where the rates of phase separation and gelation are comparable, the phase separation process does not go to completion. For deep quenches after the onset of gelation, the wavevector at maximum scattered intensity k m remains unchanged with time, while the peak intensity exhibits a slow growth. Micrographs of the phase separated domains reveal a connected structure on length scales of hundred microns superimposed on an underlying finer network structure due to gelation. Similarly gelation pins down viscous fingering patterns when a poor solvent is injected into gelatin.