Interdiffusion behavior under a temperature gradient field in a poly(ethylene-co-hexene)/poly(ethylene-co-butene) system

Abstract

We have investigated the interdiffusion of two dissimilar polymer species with different molecular masses, M_w, thus having different self-diffusion coefficients D*. A net mass flux across the interface and displacement of the original interface, Δx, between the two polymer films are observed. The displacement of the original interface moves toward the side containing the faster moving polymer species. We also examine the effect of an in-plane stationary temperature gradient on the interdiffusion of two dissimilar polymer species. As the low M_w polymer species is in the region of high temperature under the thermal gradient temperature field, the interface between the two polymer films moves faster compared with the system with the low M_w polymer species in the cold region of the temperature gradient field. We suggest that the in-plane thermal gradient accelerates polymer migration through the enhancement in polymer diffusion along the direction of the temperature gradient due to the Soret effect. We also find that the interdiffusion of polymers depends on the composition in the blend system. For a statistical copolymer system of plastic poly(ethylene-co-hexene) (PEH) and elastic poly(ethylene-co-butene) (PEB), having technologically interesting plastic and elastic properties, the diffusion of the relatively slow diffusion species (PEH) increases with the increase of PEB composition. Under the thermal gradient field the net mass flux across the interface and the movement of original interface between two polymer films can be controlled by the direction of the temperature gradient and composition of the blend system.