Rheology and dynamics in polymeric nano-composites

Polymeric nano-composites are formed when nanometer sized inorganic particles (nano-fillers) are introduced into the polymeric matrix. Controlling the attributes of the nano-fillers, such as their surface area and their interaction with the polymeric matrix, offers the possibility of the development of a new class of materials. However, there is a fundamental gap in the knowledge by which these small nano-scale particles enhance the properties of the material. In this dissertation, we use Molecular Dynamics simulations to determine the dynamic role these nano-filler particles play in the development of rheology of these polymeric systems.; The main objective of our research is to develop an essential understanding of how the rheological properties of the polymeric matrix are affected by its interactions with the nano-particles and the properties of the nano-particles. The thesis is divided into three main sections. First, we examine the equilibrium properties of the nano-composite, second, we study the rheology of the nano-composite, and third, we extend our studies to other systems such as polymer blends, where we examine the role of the nano-filler on the interfacial properties of the system.; Our studies on the equilibrium properties of the nano-composite reveal that a transition from a dispersed state to a percolated state occurs when the volume fraction of nano-particles exceeds 5%. We examine the role of this percolated state on the dynamics of the nano-composite. We observe the effect of shear on the ability of the percolating clusters to affect chain orientations. Our results show that the nano-particle causes extensive shear thinning in the material and that this shear thinning is a result of the ability of the nano-particle to induce a large orientation in the chain. In addition, we examine the role of the mobility of the nano-filler in inducing shear thinning. We find that mobile fillers cause much larger orientations in chains (in the direction of the shear flow) when compared to static simulations. We also use our simulations to study dynamic effects in polymer blends. We find that the presence of the interface can strongly influence the dynamics of polymer blends under shear.