THE DYNAMICS OF THERMAL-INDUCED PHASE-SEPARATION IN PMMA SOLUTIONS

Small-angle light scattering and scanning electron microscopy (SEM) ha ve been used to study morphology development in poly(methyl methacryla te) membranes formed by the thermal inversion method. Analysis of the early time behavior of the scattered intensity in terms of Cahn-Hillia rd theory establishes spinodal decomposition as the mechanism of phase separation for the conditions studied. The intensity maximum position for late-stage growth follows a power law dependence with a time expo nent of approximately one-third, which is consistent with diffusive co arsening mechanisms. Solutions quenched to regions of the phase diagra m below the glass transition temperature show an immediate arrest in t he location of the scattered intensity maximum, indicating a locking-i n of the phase-separated structure. Domain sizes obtained from SEM mea surements of annealed, quenched samples are shown to be consistent wit h light scattering measurements.