Nam. Verhaegh et al., FLUID-FLUID PHASE-SEPARATION IN COLLOID-POLYMER MIXTURES STUDIED WITHSMALL-ANGLE LIGHT-SCATTERING AND LIGHT-MICROSCOPY, Physica. A, 230(3-4), 1996, pp. 409-436
Mixtures of colloidal silica spheres and polydimethylsiloxane in cyclo
hexane with a colloid-polymer size ratio of about one were found to ph
ase separate into two fluid phases, one which is colloid-rich and one
which is colloid-poor. In this work the phase separation kinetics of t
his fluid-fluid phase separation is studied for different compositions
of the colloid-polymer mixtures, and at several degrees of supersatur
ation, with small angle light scattering and with light microscopy. Th
e small angle light scattering curve exhibits a peak that grows in int
ensity and that shifts to smaller wave vector with time. The character
istic length scale that is obtained from the scattering peak is of the
order of a few mu m, in agreement with observations by light microsco
py. The domain size increases with time as t(1/3), which might be an i
ndication of coarsening by diffusion and coalescence, like in the case
of binary liquid mixtures and polymer blends. For sufficiently low de
grees of supersaturation the angular scattering intensity curves satis
fy dynamical scaling behavior.