Poly (ethylene oxide) clay nanocomposites: From gels to multilayered films pp.75-144
Authors: (Eduard A. Stefanescu, Virginia Commonwealth University, School of Engineering, Department of Chemical and Life Science Engineering, Richmond, VA)
Abstract: Supramolecular polymer-nanoparticle composites combine the advantages of tailored nanometer structures with self-assembly on all length scales. Design and fabrication of polymer-nanoparticle electrolytes from solutions and gels would allow for solid polymer electrolytes to be shaped around nearly any form. Due to its flexible chain structure, beneficial for ionic transport, and due to its ability to act as a solid solvent for many metal salts, poly(ethylene oxide), PEO, is among the most extensively used polymers for fabricating solid state polymer electrolytes. Addition of nanosized clay particles with large surface area, such as Laponite and Montmorillonite, dramatically improves the ionic transport characteristics of PEO, as well as its thermo-mechanical properties. Highly ordered PEO-clay nanocomposites are complex materials that display a rich morphological behavior because of variations in composition, structure, and properties on a nanometer length scale. The ability to tailor properties to the desired application by controlling the nanoscopic structure and orientation of polymer-clay gels can optimize the materials performance for a variety of applications. Highly ordered nanocomposite films can be prepared using a layer-by-layer spreading and drying technique. The fabrication of PEO-clay multilayered films from precursor gels requires the control of polymer dissolution, clay exfoliation and knowledge of polymer-clay interactions on a nanometer length scale. In solution the clay particles can only adsorb a maximum amount of polymer until all the clay surfaces are covered. Under certain conditions, the network formed by the PEO and clay is interpenetrated by a sub-network of interconnecting pores containing excess polymer and water. The mesh size of these networks and the orientation of the clay platelets in solution strongly influence the structure formation of the dried films. Knowledge of structure and viscoelastic properties of the gels is of critical importance to the film fabrication. The reintercalation of clay platelets in films made from exfoliated polymer-clay solutions opens the door to generating supramolecular order and hierarchical structures, which may provide a useful route in the preparation of novel materials.