Late stage spinodal decomposition in binary critical fluids: scaling function obtained over a wide q-space of 4 orders of magnitude

Space-time organization of the pattern in late stage spinodal decomposition was explored over an extremely wide q-space amounting to 4 orders of magnitude by a combined use of the time-resolved small-angle neutron and light scattering methods for a binary fluid mixture of perdeuterated polybutadiene and polyisoprene near the critical point. The scaled structure factor F(x) = S(q, t) q_m(t)³ with x = q q_m(t) was explored in detail where S(q, t) is the scattering structure factor at time t as a function of magnitude of scattering vector q and q_m(t) is the q value at the maximum of the structure factor at t. A dynamical evolution of the mean value of the absolute interface curvature H(t) was estimated evolution of the mean have a particular relationship with that of q_m(t), i.e., H(t) q_m(t) ≅ 2, both being controlled by the hydrodynamic interaction effect. The dynamical scaling law was found to be valid for the global feature of the pattern growth, i.e., F(x,t) at x < 2. However, this is not the case for the local feature, giving rise to "extrinsic" and "intrinsic" nonuniversalities in F(x,t) at x > 2.