Insights into the Interplay between Nanoparticle Interfacial Interactions and Bulk Properties of Complex Systems via Colloidal Probe AFM

The addition of a nanosized particle to materials is now a well-established method for engineering their properties. Despite the significant progress in the realm of nanoscience and nanotechnology, commercially available so-called “nanofilled”materials have a relatively small share of the market. This is the result of the challenging and tedious task of designing, processing, and mass-producing these materials for a specific application of interest. A tremendous amount of research hasconfirmed that quantifying nanoparticle (NP) interfacial interactions and correlating them to the macroscopic properties facilitate the design of nanofilled materials. Therefore, this dissertation is evolved around the fundamental task of quantifying interactions and correlating it to the dispersion of NP in a host matrix. To address the former, colloidal probe atomic force microscopy (CP-AFM) is utilized to develop a method for measuring the surface free energy (SFE) of NPs. The effect of roughness on the measurements is included by employing Persson’s model. The method is validated on several systems including polystyrene, glass, hydrophobicglass, graphene oxide (GO), and reduced graphene oxide (rGO). Interfacial energy values of GO with selected organic solvents are later calculated to predict GO’s solubility in different solvents using a proposed mean-field lattice model. The modelcan successfully predict the experimentally observed solubility trend and be deployed as a decision-making tool for choosing solvents for rGO. As the final contribution, a model based on the concept of Boltzmann distribution is proposed to predict the uneven distribution of NPs in immiscible biphasic systems such as emulsions and polymer blends. This model demonstrates that factors such as NP’s size and shape, temperature, the possibility of it forming a chemical bond with the molecules of host matrix, and finally entropic contributions can be as important as the wetting coefficient in determining NP's localization. As there has been no systematic investigation of the factors mentioned above on the selective localization of NP, the model paves the road for implementing new strategies to control the localization of NPs in biphasic systems