Effect of initial solvent concentration on the structure and property of polymer nanocomposites

In this study, we investigate how the initial solvent concentration can influence the final structure and property of the polymer nanocomposites (PNCs). To produce the PNCs, nanoparticles (NPs) and polymers are first required to disperse in a good solvent and then the dispersing solvent quickly evaporates. Previous studies found that controlling the evaporation rate of solvents or drying conditions of solution can change the structure of PNCs; however, the colloidal stability of the NP-polymer mixtures depending on the solvent concentrations has not been much considered. In the NP-polymer colloidal mixture as a precursor system of PNC, the microstructure of the NP dispersion is determined by the net interaction between particles, which may sensitively vary depending on the polymer/solvent concentration. The evaporation of the solvent accompanying the PNC manufacturing process results in a continuous change in the component concentration, which means that the interaction between particles can be continuously changed. We found that the varying initial concentrations in NP-polymer mixtures with different amount of the solvent indeed changes the initial dispersion state of the NPs, which ultimately determined the final microstructure and the physical properties of the PNCs.