Phase Separation Kinetics in Silica Sol-Gel System Containing Polyethylene Oxide. I. Initial Stage

Domain formation kinetics in gelling alkoxy-derived silica solutions containing polyethylene oxide (PEO) has been investigated. The time-resolved light scattering measurement was performed for the polymerizing solutions which underwent phase separation in the length scale of micrometer. Domain formation processes which resulted in various sizes of inter-connected morphology were examined, focusing mainly on the initial stage. For all the samples, the scattering intensity grew exponentially with time forming a single peak at a fixed wave-number in the first few tens seconds, which is the characteristic of the linearized regime of the spinodal decomposition. An analysis based on the linearized theory proposed by Cahn gave a reasonable description of the kinetic parameter of phase separation induced in various stages of the sol-gel transition.