Monte Carlo studies of the interface between two polymer melts

Abstract

By use of pseudokinetic rearrangements, the interface between two polymer melts that are mutually repulsive but otherwise identical is simulated on a five-way cubic lattice at a total volume fraction of unity. The position of the interface, which has been deliberately located at z=0, remains stable if the repulsion energy is large enough and if it is ensured in the algorithm that the ratio of the volume fractions of the two polymers is distributed sharply about unity. Conventional periodic boundary conditions were used in the x and y direction, while antiperiodic boundary conditions were introduced at z=−l z /2 and z=+l z /2 (l z being the lattice dimension in the z direction). At such an antiperiodic boundary one kind of chain is continued as the other kind if the chain stretches across that boundary and nearest neighbors are counted as the same if they are different (and as different if they are the same), thus avoiding the need for a hard boundary. The interface appears to be thicker and local energies are lower than predicted by mean field theories. At the interface it is seen that chain ends and, in case of polydisperse polymers, smaller chains migrate preferentially into the opposite melt while chain dimensions perpendicular to the interface are decreased