Selective and Responsive Nanopore-Filled Membranes

Abstract

Abstract : The overall goal of this project is to develop a new class of breathable barrier membrane (i.e., selective for water vapor over harmful agents) with stimuli-responsive capabilities and the mechanical strength required for protective clothing for chemical and biological defense. These new materials are based on polymer-polymer nanocomposites of hydrophilic ionic polymer gels within a hydrophobic polymer host matrix. The specific tasks of this project include (1) synthesizing stimuli-responsive selective membranes based on polymer-polymer nanocomposites, (2) measuring transport properties: breathable barrier selectivity and electrical stimuli-responsive capabilities, and (3) measuring and modeling multicomponent transport properties and materials optimization. This work focuses on two new membrane concepts: (1) Nanopore-Filled Membranes and (2) Encapsulated Nanofiber Mesh Membranes. The goals of this project were accomplished, where the details of these results are documented in the annual reports and attached manuscripts. A recent result from this work of interest is the fabrication and super conducting properties of Nafion nanofibers, which was recently published in a high-impact journal Nano Letters. In this paper, we reported the high proton conductivity of single high purity Nafion nanofiber (1.5 S/cm), which is an order of magnitude higher than the bulk Nafion film (~ 0.1 S/cm). We also observed a nanosize effect, where proton conductivity increases sharply with decreasing fiber diameter. X-ray scattering provides a rationale for these findings, where an oriented ionic morphology was observed in the nanofiber in contrast to the isotropic morphology in the bulk film. This work also demonstrates the successful fabrication of high purity Nafion nanofibers (~ 99.9 wt%) via electrospinning and higher humidity sensitivity for nanofibers compared to the bulk.