Structure, surface excess and effective interactions in polymer nanocomposite melts and concentrated solutions

The structure, effective forces, and thermodynamics in dense polymer-particle mixtures were analyzed using the Polymer Reference Interaction Site Model (PRISM) theory. Depletion interactions, induced by polymer were quantified through the particle-particle pair correlation function and potential of mean force. It was found that a transition from monotonic decaying, attractive depletion interactions to much stronger repulsive-attractive oscillatory depletion forces took place at nearly the semidilute-concentrated solution boundary. The results show that the particle-particle potential of mean force shows multiple qualitatively different behaviours which rely on the strength and spatial range of the polymer-particle attraction.