Phase-separation dynamics in binary polymer blends

We study a continuum model for phase-separation in binary polymer blends ba sed on the Cahn-Hilliard equation with the Flory-Huggins-De Gennes free-ene rgy functional and a concentration-dependent mobility. The model is solved analytically, by means of the self-consistent large-n limit approach, and n umerically for values of the parameters corresponding to the weak and stron g segregation limits, for both critical and off-critical blends. For deep q uenches me identify a complex structure of intermediate regimes and crossov ers and the existence of a time domain characterized by the pinning of the phase-ordering process. The duration of this stop is analytically computed and diverges differently when the chains length is increased or the tempera ture is lowered. This result allows the interpretation of recent experiment s which show pinning in off-critical polymeric mixtures suggesting that the continuum model contains sufficient physical ingredients to explain the ex perimental evidence.