KINETICS OF SPINODAL DECOMPOSITION IN A POLYMER MIXTURE

The early-to-late stage of spinodal decomposition in a critical mixture of polystyrene and polymethylphenylsiloxane was studied by time-resolved light scattering over 1.8 < k < 21.1 mum-1 and 0 < t < 502 h, with k and t being the wave number and the elapsed time after temperature quench into the spinodal region, respectively. The time dependences of the maximum intensity of the scattered light I(m) and of the corresponding wave number k(m) were represented by the power laws; I(m) is-proportional-to t(beta) and k(m) is-proportional-to t(-alpha) with alpha = 0 in the early stage, alpha = 0.17 in the intermediate stage, and beta = 1.08 and alpha = 0.36 satisfying beta = 3alpha in the late stage. The behavior in the early stage was well expressed by the Cahn-Hillard theory. These exponent values are almost the same as those observed for Fe-Cr alloys. The behavior of the scaled structure factor in the late stage was expressed by a k-6 dependence in k(m) < k < 2k(m) and by a k-4 dependence in k > 2k(m), in good agreement with the recent theoretical prediction.