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 μ${\mathrm{m}}^{\mathrm{-}1}$ 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 ${\mathit{I}}_{\mathit{m}}$ and of the corresponding wave number ${\mathit{k}}_{\mathit{m}}$ were represented by the power laws; ${\mathit{I}}_{\mathit{m}}$∝${\mathit{t}}^{\mathrm{\beta }}$ and ${\mathit{k}}_{\mathit{m}}$∝${\mathit{t}}^{\mathrm{-}\mathrm{\alpha }}$ with α=0 in the early stage, α=0.17 in the intermediate stage, and β=1.08 and α=0.36 satisfying β=3α 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 ${\mathit{k}}^{\mathrm{-}6}$ dependence in ${\mathit{k}}_{\mathit{m}}$<k2${\mathit{k}}_{\mathit{m}}$, in good agreement with the recent theoretical prediction.