Viscosity, Rheological and Morphological Properties of Sulfonated Poly(ether ether ketone): PEM Fuel Cell Membrane Material

Abstract Viscosity and rheological properties of sulfonated poly(ether ether ketone) (SPEEK) have been investigated. Viscometric data were correlated by different models for polyelectrolytes. Results of viscosity for SPEEK show the characteristic properties of polyelectrolytes. Effects of parameters such as degree of sulfonation (DS), temperature, and type of solvents were investigated. Dynamic and steady shear measurements were carried out in an ARES rheometer at room temperature. It was observed that the degree of sulfonation (DS) and the solution concentration have an enormous effect on the rheological properties such as storage modulus, G′ and dynamic viscosity (η′). Membranes (thickness, ∼100 µm) were prepared by solution casting method using three different solvents, namely, N,N‐Dimethylacetamide, Dimethylsulfoxide and N,N‐Dimethylformamide. Scanning electron microscopy (SEM) and DSC studies were also carried out to study the morphological properties of these membranes. The degree of sulfonation (DS) of SPEEK, the solvent type and the temperature were found to have pronounced effects on the viscosity and rheological properties. SPEEK showed better properties in DMAc and results of SEM and DSC also confirm that membranes prepared in DMAc showed uniform morphology and higher thermal stability. These viscosity and rheological parameters give insight about the interaction of SPEEK with DMAc and these results can be helpful for membrane fabrication.