(298d) Impact of Solvent Quality On Nanoparticle Dispersion in Semidilute and Concentrated Polymer Solutions

Our objective is to quantify the impact of solvent quality on the dispersion of polymer-grafted nanoparticles in semidilute and concentrated polymer solutions. These systems are ubiquitous to industry (e.g., paints, coatings, cosmetics) and medicine (e.g., blood, proteins, pharmaceuticals); however, the factors that control nanoparticle dispersion, such as interfacial wetting, solution temperature and solvent quality, have not been well elucidated. To this end, we use photon correlation spectroscopy to capture the dynamics of polydimethylsiloxane-grafted nanoparticles (PDMS-g-silica) in simple bromocyclohexane solutions as well as complex semidilute and concentrated PDMS-bromocyclohexane solutions. Bromocyclohexane is a theta solvent for PDMS and we vary the temperature to quantify the effect of good, theta, and poor solvent conditions on wetting of the graft polymer and nanoparticle dispersion . Moreover, we use static light scattering to quantify the interactions between the PDMS-g-silica nanoparticles through their second virial coefficient, which we seek to compare to those derived from theory. By relating experiment and theory our ultimate goal is to develop general results for predicting nanoparticle stability in semidilute and concentrated polymer solutions under conditions of variable solvency.