Structure and gas transport characteristics of triethylene oxide-grafted polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene

Polymeric membrane-based gas separation technology has significant advantages compared with traditional amine-based CO(2)separation method. In this work, SEBS block copolymer is used as a polymer matrix to incorporate triethylene oxide (TEO) functionality. The short ethylene oxide segment is chosen to avoid crystallization, which is confirmed by differential scanning calorimetry and wide-angle X-ray scattering characterizations. The gas permeability results reveal that CO2/N(2)selectivity increased with increasing content of TEO functional group. The highest CO(2)permeability (281 Barrer) and CO2/N(2)selectivity (31) were obtained for the membrane with the highest TEO incorporation (57 mol%). Increasing the TEO content in these copolymers results in an increase in CO(2)solubility and a decrease in C(2)H(6)solubility. For example, as the grafted TEO content increased from 0 to 57 mol%, the CO(2)solubility and CO2/C(2)H(6)solubility selectivity increased from 0.72 to 1.3 cm(3)(STP)/cm(3)atm and 0.47 to 1.3 at 35 degrees C, respectively. The polar ether linkage in TEO-grafted SEBS copolymers exhibits favorable interaction with CO(2)and unfavorable interaction with nonpolar C2H6, thus enhancing CO2/C(2)H(6)solubility selectivity.