Room temperature ionic liquids (RTILs) are salts with low melting points (often below room temperature), and are typically comprised of quaternary sulfonium, phosphonium, or ammonium (imidazolium, pyridinium, pyrrolidinium) cations paired with anions of low Lewis basicity (BF4-, PF6-, CF3SO3- (CF3SO2)2N-, etc.). Today the utility of RTILs in advanced electrochemical devices ranging from lithium ion batteries, to fuel cells, capacitors, solar cells and actuators is being explored. Because of the mobility of both the anionic and cationic components of ionic liquids, it is proposed that the function of such devices might be improved if solvated membranes or conventional ionic liquids were replaced by film-forming ionic liquid polymers in which the mobility of the ions is constrained. However, when the mobility of the anionic and cationic components in ionic liquids is reduced by incorporation in a polymer system, ionic conductivity is also substantially impacted. This limitation can possibly be mediated by reduction of the dimensionality of ion diffusion in nanostructured, precision block copolymers and polymer blends. The present proposal outlines options for the synthesis and characterization of ionic liquid 1,3-dialkyl-4- and 5-vinylimidazolium salts that are amenable to facile homopolymerization or incorporation as block sequences in a wide variety of vinyl- and acrylic copolymer systems. In addition, the potential device utility of polymer blends and block copolymer systems containing these imidazolium polymers is highlighted. Specific goals of the research are to synthesize and characterize families of dissymmetric, aprotic ionic liquid monomers formally derived from 1-methy-4- and 5-vinylimidazoles, 2-alkyl-1-methyl-4- and 5-vinylimidazoles and 1-methyl-4-and 5-vinylimidazole-2-propane sulfonate; elucidate options for the homopolymerization, random copolymerization and block copolymerization of these monomers; characterize the thermal and electrochemical properties of these monomers and polymers; and, study the thermal and electrical properties, and morphology of blends of polymers of 1,3-dialkyl-4-vinylimidazolium salts with PVF2.
NON-TECHNICAL SUMMARY:
Room temperature ionic liquids (RTILs) are salts with low melting points, often below room temperature. Today, the utility of RTILs in advanced electrochemical devices ranging from lithium ion batteries, to fuel cells, capacitors, solar cells and actuators is being explored. Nevertheless, only limited success has been achieved in practical applications. Because of their liquid state, the function RTILs in commercial devices might be improved if they were replaced by film-forming ionic liquid polymers. However, incorporation in a polymer system typically results in a substantial drop in ionic conductivity. This limitation can possibly be overcome in precision 2-D or 1-D nanomaterials. The present proposal outlines options for the synthesis and characterization of nanomaterials derived from ionic liquid polymers. Specific goals of the research are to synthesize and characterize new ionic liquid monomers; elucidate options for the preparation of nanocomposites; and, evaluate the morphology, thermal properties and electrochemical characteristics of these materials. Novel materials, that can be fabricated with the agency of the poly(ionic liquids), described in the present proposal, might be the key to commercial utility of an ionic liquid system in robust light-weight electronic devices ranging from Li ion batteries to photovotaics and fuel cells. Recent reports that imidazolium-based RTILs are excellent solvents for the dispersion of carbon nanotubes, and that the intrinsic structure and properties of the carbon nanotubes are retained after dispersion might be translated into practical device options by utilizing these new poly(ionic liquids). The research will be carried out at the Rochester Institute of Technology (RIT), a comprehensive university, offering terminal M.S. degrees in Chemistry and MS&E, and providing meaningful research experiences to graduate and undergraduate students alike. Three graduate students and two undergraduate students will be directly trained and mentored. In addition, the PI will mentor a summer student in the Syracuse/RIT, NSF Louis Stokes Alliance for Minority Participation - Upstate Alliance, and an ACS Project SEED student. A unique collaboration with Peggy Cebe (Tufts University), characterizing the crystal habit of polymer composites and providing research experiences to deaf and hard-of-hearing students will also be supported.
