ENTROPY-INDUCED FROZEN MORPHOLOGY IN UNSTABLE POLYMER BLENDS

We report the arrest of spinodal decomposition for thermodynamically unstable off-critical polymer blends. A coarsening mechanism based on the entropic barrier created for the transport of long chains across sharp interfaces between the phase-separated domains can explain this novel feature characteristic of polymer blends. The relative contributions of the enthalpic and entropic parts of the free energy of an inhomogeneous polymer mixture to the kinetics of phase separation are computed. For polymers the entropic contribution dominates and leads to the emergence of a transnodal regime.