Nanoscale Morphologies and Selective Solvents to Promote Cation Transport in Polymers

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

PART 1: NON-TECHNICAL SUMMARY The fundamental understanding of ion transport mechanisms in polymers is incomplete, while the demands for improved membrane properties increase particularly regarding separation technologies and electrochemical device applications. This project endeavors to develop this fundamental understanding through the comprehensive characterization of newly designed and synthesized polymers containing sulfonate groups. The research approach includes conductivity measurements, spectroscopy measurements, and extensive nanoscale structural characterization to establish the location and motion of ions under various conditions of temperature and solvent content. To accomplish this experimental plan, the research team will design and build environmental chambers to maintain a saturated solvent environment during in situ testing. Mirroring the working environment in the materials industry, the PI and graduate students actively collaborate with synthetic chemists and computational scientists, to holistically develop and evaluate the understanding of ion transport mechanisms. By establishing how ions move through polymers, scientists and engineers will be able to design new polymers and processing routes to optimize ion conductivity and ion selectivity that meet a variety of specific needs and drive innovation. PART 2: TECHNICAL SUMMARY This research effort aims to understand to what extent nanoscale morphologies and selective solvents promote cation transport and the underlying mechanisms of cation transport. The proposed research combines structural characterization, conductivity measurements, and spectroscopy measurements on unique polymers to further develop the understanding and demonstration of decoupled ion motion in polymer electrolytes. Aim 1 endeavors to achieve the double gyroid morphology in strictly alternating multiblock copolymers near room temperature. We will investigate a variety of multiblock copolymers and processing strategies to determine the criteria for producing the double gyroid morphology in multiblock copolymers with strongly segregated and short blocks. Aim 2 will identify solvent attributes that promote Li+ and Na+ transport in polymers with aligned nanoscale layered morphologies. To eliminate the effect of morphological orientation and grain boundaries on transport in periodic nanoscale morphologies, we will fabricate thin films with aligned layers in strictly alternating multiblock copolymers and measure the in-plane conductivity as a function of solvent swelling and solvent type. Finally, Aim 3 seeks to improve ion transport in polymers with network morphologies by the addition of solvent. For this portion of the proposed project, we will study three types of partially sulfonated polymers that self-assemble into nanoscale ionic channels without long-range order. This broader range of polymers will test the applicability of our findings about solvent-enhanced ion transport in a variety of nanostructured polymers. In addition to providing exceptional opportunities for student education, this proposal will develop an environmental chamber for grazing incident X-ray scattering and provide professional development workshops for doctoral students. 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.