Solubility Studies of the Nafion ® perfluorosulfonated ionomer

This thesis describes an investigation into routes for the solubilisation of Nafion® membrane. Nafion® membrane in the protonated, lithium, sodium and potassium cation forms has been dissolved at high temperature and pressure in an autoclave. Solvent blends of water and either methanol, ethanol, 1-propanol or 1-butanol were used and solution concentrations of up to 15 wt% were achieved. The effect of temperature and time at temperature have been investigated for this autoclave method. Solutions made in this way have been concentrated by solvent evaporation to yield solutions of about 30 wt% Nation®. A promising method to dissolve Nafion® in a microwave acid digestion bomb in water/ alcohol blends has also been developed. Reflux dissolution has also been used to produce Nafion® solutions. Swelling experiments have been undertaken to help establish optimum solvent blends for the solubilisation process. A solubility parameter is proposed from a swelling study and is further investigated by a new procedure involving contact angle measurements. The properties of films cast from resulting Nafion® solutions and the melt flow properties of Nafion® powders in the protonated and tetrabutylammonium cation forms are also reported. The technological target of this work was to establish the ideal route for the dissolution of Nafion® membrane and the optimisation of high concentration solutions, which has been achieved.