Gas transport properties of Poly(ether-b-amide) segmented copolymers: The role of the degree of microphase separation in amorphous regions

Polyether-based crystalline multiblock copolymers have been employed as membrane materials for the removal of CO2 from light gases due to their excellent gas permeability and selectivity. However, the influence of the nature of the crystalline and amorphous regions on gas permeability needs to be deeply explored. In this work, the effect of the phase structure, especially the degree of microphase separation (DPS) in the amorphous regions, on the gas transport properties of poly(ether-b-amide) (PEBA) segmented copolymers has been studied. It was found that the amorphous domain consists of two partially mixed phases enriched either with poly(tetramethylene oxide) (PTMO) or with polyamide 1012 (PA1012). The effect of annealing on the microphase structure in the crystalline and amorphous regions was investigated by X-ray scattering techniques. The DPS was found to be inversely correlated with the crystallinity of the hard segments. Gas permeability measurements confirmed that for PEBA membranes with lower crystallinity, weak microphase separation favors gas permeability. All these findings provide a simple method to modulate the degree of microphase separation by varying the crystallinity of the hard segments. Additionally, this work shed light on the synergistic effects of these factors on gas permeability, providing valuable guidance to enhance the performance of gas separation membranes.