Small-Angle X-Ray-Scattering Study of Spinodal Decomposition in Polystyrene Poly(styrene-co-bromostyrene) Blends

Abstract

Structure factors of polystyrene/poly(styrene-co-bromostyrene) blends and their change with time during phase separation were studied by small-angle X-ray scattering. Structure factors in thermal equilibrium show the form given by the random phase approximation. Measurement of absolute scattering intensities for blends of different composition enables a determination of the radii of gyration of the blend Components. Evolution of structure after a temperature jump from the mixed state into the two-phase region is in accordance with the predictions of the latest theories. The initial kinetics can be described by an equation of motion that includes relaxation times and a virtual structure factor. Application of the theory enables a determination of relaxation times dependent upon the wave vector. At temperatures near the glass transition, relaxation and growth become nonexponential.