Generalized Flory equations of state for hard heteronuclear chain molecules

Abstract

The generalized Flory (GF) and generalized Flory-dimer (GFD) equations of state have been extended to fluids containing hard heteronuclear chain-like molecules. Compressibility factor expressions have been derived for block, alternating and random ‘‘copolymer’’ fluids. The effect of composition and the relative size of the segments of a heteronuclear chain on the compressibility factor are studied. We have also performed molecular dynamics computer simulations on these systems using an extension of Rapaport’s algorithm in which the chains are effectively treated as hard spheres of different sizes held together by invisible strings. The compressibility factors predicted by the GFD theory for heteronuclear chain fluids are in very good agreement with our computer simulation results. The predictions of Chiew’s Percus Yevick theory are also in very good agreement with our computer simulation results on block copolymers.