Insights into the impact of a green polar solvent on the properties of polysulfone membranes for gas separation applications

Abstract

Replacing toxic solvents with greener options in the preparation of polymer solutions and subsequent membranes is a matter of importance today. This study focused on the use of methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (MDMO) as an environmentally-friendly alternative to N-methylpyrrolidone (NMP) for the preparation of thin polysulfone films. The correlation between the thickness of the prepared membranes and the concentration and viscosity of the polymer solutions used was evaluated. Attention was also paid to the presence of residual solvents, which were investigated by Fourier-transform infrared spectroscopy, thermogravimetric analysis, headspace gas chromatography, and dynamic mechanical analysis. Gas permeation measurements were performed for three gases (CO2, N2 and O2) with different kinetic diameters of molecules. Although MDMO proved to be a good solvent for polysulfone, the tested cast films did not exhibit the same gas permeability as membranes prepared from polysulfone solutions based on N-methylpyrrolidone.