Pebax-polydopamine microsphere mixed-matrix membranes for efficient CO2 separation

Novel facilitated-transport mixed-matrix membrane (MMM) were prepared through the incorporation of polydopamine (PDA) microspheres into a poly(amide-b-ethylene oxide) (Pebax MH 1657) matrix to separate CO2-CH4 gas mixtures. The Pebax-PDA microsphere MMMs were characterized by Fourier transform infrared spectroscopy, scanning electron microcopy, X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The PDA microspheres acted as an adhesive filler and generated strong interfacial interactions with the polymer matrix; this generated a polymer chain rigidification region near the polymer-filler interface. Polymer chain rigidification usually results in a larger resistance to the transport of gas with a larger molecular diameter and a higher CO2-CH4 selectivity. In addition, the surface of PDA microspheres contained larger numbers of amine, imine, and catechol groups; these were beneficial to the improvement of the CO2 separation performance. Compared with the pristine Pebax membrane, the MMM with a 5 wt % PDA microsphere loading displayed a higher gas permeability and selectivity; their CO2 permeability and CO2-CH4 selectivity were increased by 61 and 60%, respectively, and surpassed the 2008 Robeson upper bound line. (C) 2016 Wiley Periodicals, Inc.