Kinetics of Relaxation and Unmixing in Polymer Blends as Studied by X-Ray-Scattering

Abstract

Concentration fluctuations in polystyrene/poly(styrene-co-bromostyrene) blends and changes induced by temperature jumps were studied by small-angle X-ray scattering. Structure factors in thermal equilibrium show the form given by the random phase approximation. Kinetics of structure changes after T-jumps within the homogeneous phase or jumps from the mixed state into the two-phase region are in accordance with the predictions of latest theories, being described by a simple equation of motion. Application of the theory enables a determination of relaxation times dependent upon the wave vectors. At temperatures near to the glass transition, relaxation and growth become nonexponential.