Monte Carlo simulations of symmetric polymer blends. II. Chain properties in interface regions

Abstract

Making use of a previously introduced lattice model for binary polymer blends of limited miscibility Monte Carlo simulations have been performed in order to investigate the influence of different thermodynamic conditions on mass segregation and global structure as well as on microstructure of homopolymers when passing from one bulk phase through the interface to the other. The calculations show an enrichment of shorter chains at the interface as well as a decreasing miscibility with decreasing average chain length (at constant bulk density) of the polymer matrix on the one hand and relate the compression of the coils at the interface to the observed orientation and deformation effects on the other. Surprisingly, an additional expansion of the polymer coils (belonging to the minority component) can be found at some distance from the actual interface due to attractive interactions between pairs of chains in rather “diluted” layers. Furthermore, all phenomena are discussed from two different viewpoints: (i) The average chain length is kept constant while the energy parameter is varied, and (ii) the chain length is varied and the bulk densities are held constant by use of identical relative energy parameters.