Nonlinear diffusion and phase separation

Non-Fickian diffusion driven by gradients in chemical potential rather than concentration is important for nonideal mixtures, Conventional formulation s of the chemical potential must be supplemented by gradient term whenever phase separation is possible, Equilibrium composition profiles are predicte d in both confined and large systems using the Landau-Ginzburg functional, Parameter estimates based on mean-field theories work well for polymers, Th e dynamics of phase change are described by the modified Cahn-Hilliard equa tion, Domain growth in quiescent systems occurs by Ostwald ripening and by hydrodynamics induced by concentration gradients. Simulations without adjus table constants are used to predict non-equilibrium morphologies in binary and ternary polymer, Experimentally confirmed morphologies include dual-con tinuous phases, dual-dispersed phases, core-shell particles and more comple x structures, Most impurities are enriched at the phase boundaries. (C) 200 1 Published by Elsevier Science Ltd.