Effect of the Interactions between Polymers and Solid Fillers on the Structure of Polymer-Filler

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As a conclusive stage of the first project period that logically extends its findings, the currently proposed project aims at gaining fundamental, comprehensive understanding of the effects of the interaction of polymers with solid fillers on the structure of the filler-polymer interfaces, polymer mediated forces, filler agglomeration and associated rheological properties of the filled polymer melts. Relying on the proposed theoretical development, we intend to calculate the polymer mediated force acting between fillers as a function of the filler separation, polymer density, affinity of the filler surface for the adsorbed polymers, and the degree of polymerization of polymers. In addition, we will investigate the density structure of the adsorbed polymer layers depending on the micoscopic interactions between the filler surface and polymers. We will use the Density-of-state Monte Carlo simulations to calculate the polymer mediated force and the structure of the adsorbed polymer layers with the objective to verify our theoretical findings. Using the calculated polymer-mediated interactions as an input, we will obtain the equation of state of the polymer-particle composite in the presence of the adsorption interactions between the fillers and polymers. In addition, we intend to investigate the polymer-induced phase separation in the particle-colloid composites and use the result in explaining the polymer bridging-assisted filler aggregation in the polymer particle mixtures. In the proposed theoretical approach, we will separately describe the cases of reversible and irreversible polymer bridging among fillers. For the case of irreversible bridging by polymers, we will investigate the 'bridging flocculation' of the fillers in the polymer melts and the formation of filler cluster aggregates (flocs) based on the exact statistical physical model. This study includes investigating the polymer-mediated interactions among flocs and their effect on the shear viscosity of the filled polymer melt. In the final stage of the proposed project, we will study the selected rheological properties of filled melts starting from microscopic polymer-filler and resulting polymer-mediated filler-filler interactions, through developing and making use of the self-consistent dynamic model incorporating those interactions.