Kinetics of phase separation in polymer mixtures: a molecular dynamics study.

We present detailed results from a molecular dynamics (MD) simulation of phase-separation kinetics in polymer mixtures. Our MD simulations naturally incorporate hydrodynamic effects. We find that polymeric phase separation (with dynamically symmetric components) is in the same universality class as segregation of simple fluids: the degree of polymerization only slows down the segregation kinetics. For d = 2 polymeric fluids, the domain growth law is L(t) ∼ t(ϕ) with ϕ showing a crossover from 1/3 → 1/2 → 2/3. For d = 3 polymeric fluids, we see the crossover ϕ = 1/3 → 1. Our MD simulations do not yet access the inertial hydrodynamic regime (with L ∼ t(2/3)) of phase separation in 3-d fluids.