Dynamics of complex interfaces. II. Diffusion and morphology

In this contribution, we theoretically investigate the isothermal mass transport of a simple fluid into a blend of two immiscible Newtonian polymers. Using internal state variables, we derive a nonlinear formulation that addresses the effects of the diffusion/interface coupling on both the mass transport as well as on the morphology of the interface. The approach uses a scalar and a second-order tensor to directly track the dynamic changes of the size and shape of the interface. The mass flux governing equation includes new terms that lead to non-Fickian behavior attributed to the viscoelatic contribution of the interface. In turn, the size and shape of the interface are modified by diffusion. In one-dimensional analysis, we examine the nature of propagation of both nonlinear hyperbolic and linear dispersive waves. Explicit formulas for the characteristic speed, phase velocity, and attenuation are provided. © 2003 American Institute of Physics. @DOI: 10.1063/1.1571053#