This research in a primarily undergraduate institution (RUI award) is focused on the development of a new type of polymeric rubber material which, unlike commercial rubber materials, would be recyclable. The chemistry used to make this new material also would allow for the rubbery properties to be turned on and off using electricity. The result of a successful project would be a material that could be converted from a liquid to a rubber at the flip of a switch. Additionally, these materials could be designed to display a color that indicates whether the material is rubbery or not. The color would change when the material has been chemically, electrically, or mechanically weakened to provide a visual warning that the material may not work as expected. This new class of materials could enable new technologies such as electrically controlled rubbers for use in advanced vibration/impact damping systems or in gaskets that change color when in need of replacement.
Beyond potentially enabling new technologies, the pursuit of this research will allow for advanced research training of up to 20 undergraduate students over three years. It will also expand the materials research infrastructure at Appalachian State University, enabling faculty there to continue materials research for years to come.
In this research project, 2,2'-bipyridine-terminated poly(dimethylsiloxane) (PDMS) chains will be synthesized and blended with various metal salts (e.g. iron (II) chloride) to create metal coordination complex crosslinked polymer networks (MC3PN)'s. These MC3PN's will subsequently be characterized with UV/Vis spectroscopy, cyclic voltammetry, differential scanning calorimetry, and dynamic mechanical analysis to better understand the relationship between the molecular structure and the resulting properties. In the course of the proposed research, the answers to the following five questions will be sought. 1) Is the metal-ligand binding sufficiently stable to serve as crosslinks and impart the MC3PN with elastomeric properties at room temperature? 2) Can altering the network structure (e.g. cross-link density) be used to tailor the mechanical properties of the elastomeric MC3PNs in the same manner that conventional covalently crosslinked elastomer properties (e.g. stiffness and strength) can be tailored? 3) Can the metal coordination complexes be reversibly and controllably un-crosslinked through the introduction of chelating ligands, redox processes, or a change in temperature? 4) Can the color imparted to the MC3PNs by the metal coordination complexes be used to ascertain the degree to which the material is crosslinked and from this to infer the mechanical properties (such as impending failure of the material)? 5) Can the self-assembly of metal coordination complexes impart self-healing properties to the elastomeric material?
Beyond potentially enabling new technologies, the pursuit of this research will allow for advanced research training of up to 20 undergraduate students over three years. It will also expand the materials research infrastructure at Appalachian State University, enabling faculty there to continue materials research for years to come.
