Hairy Nanoparticles PDF Download

Polymer grafted nanoparticles have been of increasing scientific interest due to their potential applications in numerous fields. They have emerged as model systems to understand the structure, dynamics and phase stability of molecular and atomic liquids. One such class of polymer-tethered nanoparticles are the self-suspended hairy nanoparticles created by covalent attachment of polymer chains to inorganic nanostructures without any dispersing medium. The work reported in this thesis examines the flow, structural and dynamical properties of these self-suspended hybrid hairy nanoparticles with a particular emphasis on understanding the roles played by interactions between tethered chains on material structure and dynamics. By means of Small Angle X-ray Scattering (SAXS), rheology, and dielectric relaxation experiments coupled with theoretical studies, it is shown that interpenetration of the grafted polymer chains under the action of temperature, enthalpic attraction of tethered polymer chains, nanoparticle curvature size and the requirement that tethered chains must fill the inter-particle space; has a profound effect on structural, mechanical, dynamic, and transport properties of the materials. With the help of these findings the present work provides new insights into a variety of heretofore poorly understood phenomena in self-suspended materials, including observation of a stress overshoot during start-up of steady shear flow, thermal jamming, and dramatic slowing down of polymer chain dynamics. Additionally, it is shown that armed with these physical phenomena one can easily manipulate the design variables (e.g. size distribution of the core particles, polydispersity in the corona molecular weight, dispersity in corona grafting density and chemistry of the corona chains) to create novel materials with unusual property profiles. Research reported in this thesis shows, for example, that a blend of self-suspended hairy particles comprised of bi-disperse core sizes exhibits multiple yielding transitions, jamming to unjamming state transitions, and facilitates fast transport of ions in bulk electrolytes and at electrochemical interfaces. Extending these ideas to create self-suspended nanoparticle blends in which hairy particles comprised of chemically dissimilar corona, but the same core, are shown to enable even more unusual materials designs that facilitate fundamental studies of interactions across tethered polymer interfaces from high signal-to-noise bulk experiments.