Correlation effects in dilute particle-polymer mixtures

The influence of chain connectivity and polymer excluded volume correlations on macromolecule-induced depletion interactions between spherical particles in the athermal limit is analyzed based on integral equation methods. Results for the sphere-sphere second virial coefficient (B₂^cc) and polymer-induced potential of mean force derived within the Percus-Yevick (PY) and hypernetted chain (HNC) closure approximations for the polymer reference interaction site model (PRISM) are compared with those from prior theories for the depletion interaction which employ simplified models for macromolecules and/or ignore intermolecular packing effects. Distinctive differences are often found depending on system parameters, which are interpreted in terms of many-body correlation effects or nonathermal solvent quality. Comparisons with scaling and field-theoretic approaches in the dilute polymer limit, and limitations of the PY closure, are briefly addressed.