Coarsening and pinning in the self-consistent solution of polymer blends phase-separation kinetics

We study analytically a continuum model for phase separation in binary polymer blends based on the Flory-Huggins-de Gennes free energy, by means of the self-consistent large-n limit approach. The model is solved for values of the parameters corresponding to the weak and strong segregation limits. For deep quenches we identify a complex structure of intermediate regimes and crossovers characterized by the existence of a time domain such that phase separation is pinned, followed by a preasymptotic regime, which in the scalar case corresponds to surface diffusion. The duration of the pinning is analytically computed and diverges in the strong segregation limit. Eventually a late-stage dynamics sets in, described by scaling laws and exponents analogous to those of the corresponding small-molecule systems.