Role of polymer segment-particle surface interactions in controlling nanoparticle dispersions in concentrated polymer solutions.

The microstructure of particles suspended in concentrated polymer solutions is examined with small-angle X-ray scattering and small-angle neutron scattering. Of interest are changes to long wavelength particle density fluctuations in ternary mixtures of silica nanoparticles suspended in concentrated solutions of poly(ethylene glycol). The results are understood in terms of application of the pseudo-two-component polymer reference interaction site model (PRISM) theory modified to account for solvent addition via effective contact strength of interfacial attraction, ε(pc), in an implicit manner. The combined experimental-theoretical study emphasizes the complex interactions between solvent, polymer, and particle surface that control particle miscibility but also demonstrate that these factors can all be understood in terms of variations of ε(pc).