Title

Gas Permeability of Ion-Exchanged and Silicon Oxide-Filled Perfluorosulfonate Membranes

Date of Award

1995

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

Kenneth Mauritz

Advisor Department

Polymers and High Performance Materials

Abstract

In an ongoing study of the formulation of unique hybrid organic-inorganic nanocomposite materials, the sol-gel reaction is used to form silicon oxide nanoparticles within the polar clusters of perfluorosulfonate ionomer membranes. Insofar as the formulation of these composites is concerned, this research was interested in controlling all aspects of the reaction. The initialization of these membranes to render an acid to SO$\sb3\sp-$ exchange group ratio of 1:1 has been reevaluated and improved to produce a more controlled initialized state. The exchange of protons for other metal cations has also been reevaluated to mimic the initialization procedure to reduce the possibility of the polymer exhibiting structural hysteresis. Also, the incorporation of silicon oxide within these membranes has been modified to an extent to reproducibly fill the membranes with a desired amount homogeneously throughout the membrane. The necessity of a rigorous redevelopment of the SiO$\sb2$-Nafion composite formulation has been driven by the desire to use gas molecules and traditional gas transport experiments to elucidate the structure of the incorporated inorganic network. Complete homogeneity is required since gas permeation is a bulk characterization. Hence, no accurate information can be derived about the inorganic phase unless it is all the same structure. A new computer-controlled gas permeability cell console was constructed to allow simultaneous determination of the gas solubility, diffusion, and permeability coefficients for polymer membranes. The instrumental design allows for sample analysis over a wide range of temperature and pressures and permits the use of small sample sizes ($<$2.5cm diameter.).