SURFACE-INDUCED SEGREGATION OF HARD-SPHERE CHAIN MIXTURES

Structure and segregation properties of a hard-sphere chain fluid diss olved in a polymeric solvent near a hard wall are investigated using t he Percus-Yevick (PY) approximation for the associative Henderson-Abra ham-Barker (HAB) equation. Both the polymer and the solvent are modele d as freely jointed hard-sphere chains of different lengths m(p) and m (s) and with different bead diameters d(p) and d(s). It is shown that there are two segregation factors: the bead diameter and the chain len gth difference, which cause structural features of the interface. It i s determined that at low densities the segregation is mainly due to th e chain-chain length difference, while the difference in the segment d iameters is dominant at high densities. The structure is analyzed for various overall densities zeta(3) and polymer concentrations x(p). The partial density profiles as well as the segregation profiles are comp ared with Monte Carlo data to test the accuracy of the PY theory. (C) 1998 American Institute of Physics. [S0021-9606(98)51622-4].