Polar/nonpolar gas transfer through PEO-based copolymers membranes

Abstract

ABSTRACTTwo PEG-based copolymers containing two different chain extenders, as hard segments, were synthesized by 4,4′-methylenediphenyl diisocyanate (MDI). The chain extenders were 1,4-butane diol (BDO) and 1,2-ethane diamine (EDA). The application of the polyurethane (PU) and poly(urethane-urea)s (PUU)s synthesized polymers, which were characterized by Fourier transform infrared spectrometer (FTIR), differential scanning calorimetry (DSC) and atomic Force Microscopy (AFM), in the gas permeability was investigated. The obtained results indicated that by replacing the urea linkage in the polymers, the microphase separation of hard and soft segments increased. The synthesized PEG-based copolymers were semi-crystalline at room temperature. According to the DSC results, the crystallinity of the synthesized polyurethanes decreased as temperature increased. In addition, a reduction in mean surface roughness could be seen based AMF information. The gas (carbon dioxide and methane) separation properties of the polymers revealed that by replacing the urea linkage, the diffusivity, permeability and selectivity of the gases increased slightly.The solubility and diffusivity of gases indicated he solubility domination of gas transport in these membranes. However, the sorption coefficient (S) of a particular gas was surprisingly constant for the two synthesized polymers. The CO2 permeability increased with increasing feed pressure, while CH4 permeability remained almost constant at both temperatures of 25°C and 35°C. The increase in temperature led to an increase in the permeability of the gases and a decrease in the gas selectivity for the both synthesized polyurethanes.