Monte Carlo simulations of symmetric polymer blends. I. Characterization of the interface

Abstract

A new method is presented for the simulation of the interface between nearly immiscible amorphous polymer phases. Strictly speaking, two independent interfaces are developed whose positions remain fairly in place during the whole simulation process. The interface is characterized by its thickness, by the excess number of contacts between segments of different type in the interface region (a quantity being characteristic of cavities that contain the other type of polymer) as well as by the fractal dimension and the relative surface enlargement (compared to a totally flat interface) similar to the methods introduced earlier for polymer surfaces. Further quantities that are used for a proper description of the interface are density profiles of polymer segments as well as of end segments and centers of mass. A variation of the repulsive energy between the two types of polymers on the one hand and a variation of the (average) chain length on the other hand reveals that the roughness of the interface decreases with increasing immiscibility (increasing energy parameter) and decreasing chain length (when the product of energy parameter and chain length is kept constant).