CAS-Climate: Ion and Interfacial Dynamics in Polymerized Ionic Liquids

NON-TECHNICAL SUMMARY:

The rising energy needs of our society cannot be met without development of novel, high-performance, clean-energy conversion and storage devices. Electrolytes are a critical component of these devices, as these materials are the media for selective transport of the target electroactive species. However, safety, stability, and selectivity issues are an on-going concern in many state-of-the-art electrolytes.

A unique focus of the current project is the investigation of novel approaches to enhance charge transport in polymerized ionic liquids by taking advantage of confinement and interfacial interactions, which would make them suitable as electrolytes. The fundamental understanding obtained from the planned research will provide a basis for deliberate and optimal design of polymers for many sustainability-relevant technological applications, such as batteries, fuel cells, and supercapacitors, where interfaces play a significant role in determining the overall functionality.

In addition, the knowledge gained from this project concerning the impact of the chemistry of solid surfaces in contact with polymers, the type of polymer, extent of confinement and sample preparative conditions will be of benefit to the polymer science and engineering communities. An important component of this project also involves several integrated educational activities.

The project will contribute to training and education of specialists in polymer nanotechnology and materials science through active involvement of graduate and undergraduate students in this research. The proposed program emphasizes work with underrepresented groups and research experiences for high school students.

TECHNICAL SUMMARY:

Polymerized ionic liquids are a class of novel functional polymer electrolytes that combines the unique physicochemical properties of molecular ionic liquids (e.g. non-flammability, wide electrochemical windows, negligible vapor pressures, and ionic conduction) with the outstanding mechanical characteristics of polymers. These materials are promising for a variety of clean-energy applications including dye-sensitized solar cells, portable batteries, actuators, field-effect transistors and electrochromic devices.

However, their ionic conductivity, which is one of the most critical properties in the context of electrochemical energy applications, drops by many orders of magnitude in comparison to their low molecular weight counterparts upon polymerization. In the proposed project, a new approach to developing fundamental understanding for rational design of polymerized ionic liquids with high ionic conductivity and other desirable electrochemical properties will be investigated.

The overall goal of the planned research is to employ nanoscale confinement and interfacial forces to develop a fundamental framework for designing polymerized ionic liquids with enhanced ionic conduction. The major objectives of the planned work are to: (i) develop a fundamental understanding of the impact of the extent of nanoscale confinement (as reflected by the mean pore diameters and polymer film thicknesses) on polymerization kinetics, ion transport and dynamics in confined polymerized ionic liquids, (ii) unravel the role of polymer/pore-wall interactions on polymerization kinetics, ion dynamics and charge transport, (iii) investigate the effect of molecular structure (chemistry) of polymerized ionic liquids on their ion dynamics and charge transport in nanopores, and (iv) elucidate the impact of the dimensionality (type) of confinement on polymerization kinetics, ion transport and dynamics in confined polymerized ionic liquids.

The detailed fundamental understanding of the impact of nanoscale confinement gained from this project will provide a scientific framework for the design of functional polymers with relevance to sustainability and unique properties for numerous technologies, including polymer electrolytes suitable for use in electrochemical power sources and devices.

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This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.