Capillary-wave and chain-length effects at polymer/polymer interfaces

A continuum-space bead-spring model is used to study the phase behavior of binary blends of homopolymers and the structure of the interface between the two immiscible phases. Results of numerical simulations using molecular dynamics supplemented by Monte Carlo exchanges are presented. The structure of the interface is investigated as a function of immiscibility, chain length, and system size. Capillary waves are observed, and their measurements allows us to determine the surface tension. We propose a universal method of measuring the interfacial width in terms of second moments of the different contributions to the first derivative of the interfacial profile. Predictions of this method are directly verified.