Asymmetric landscapes of early spinodal decomposition

We address the effect of an asymmetric concentration-dependent mobility on the early stages of spinodal decomposition in polymer blends and solutions, and characterise it quantitatively. This is particularly important when on e of the components has a slower dynamics than the other, e.g., because it is closer to its glass transition, or is weakly cross-linked. Composition m ode coupling is proposed as the underlying physical mechanism, and then inv estigated by means of numerical simulations of the Cahn-Hilliard equation i n one (1d) and two (2d) dimensions. In general. this coupling broadens the peak in the structure factor: in 1d an asymmetric concentration profile is obtained, with sharpened interfaces, whereas in 2d the formation is favoure d of sharp peaks of the phase rich in the snore mobile component. It is sho wn how the changing morphology of this phase-separating system can be descr ibed with the aid of Minkowski functionals.