Correlation effects in dilute particle-polymer mixtures

The influence of chain connectivity and polymer excluded volume correlation s on macromolecule-induced depletion interactions between spherical particl es in the athermal limit is analyzed based on integral equation methods. Re sults for the sphere-sphere second virial coefficient (B-2(cc)) and polymer -induced potential of mean force derived within the Percus-Yevick (PY) and hypernetted chain (HNC) closure approximations for the polymer reference in teraction site model (PRISIM) are compared with those from prior theories f or the depletion interaction which employ simplified models for macromolecu les and/or ignore intermolecular packing effects. Distinctive differences a re often found depending on system parameters, which are interpreted in ter ms of many-body correlation effects or nonathermal solvent quality. Compari sons with scaling and field-theoretic approaches in the dilute polymer Limi t, and limitations of the PY closure, are briefly addressed. (C) 1998 Ameri can Institute of Physics. [S0021-9606(98)50547-8].