Jiangying Liu,Yang Pan,Jingyi Xu,Zhenggang Wang,Haipeng Zhu,Gongping Liu,Jing Zhong,Wanqin Jin
Pebax-based membranes have attracted intensive interest for high separation efficacy of carbon dioxide . For achieving excellent gas permeance, ultrathin membrane thickness is always the pursuit of composite membrane technology, in which controlling the interfacial property of the multi-layer remain a great challenge. Herein, we introduced an amphipathic copolymer polydimethylsiloxane (PDMS)-block-polyethylene oxide (PEO) (PDMS- b -PEO) into the intermediate layer to tune the interfacial adhesion, enabling fabrication of ultra-thin Pebax composite membrane. It was demonstrated that surface segregation of PEO segments not only suppressed formation of dense SiO x layer due to the plasma treatment on PDMS intermediate layer, but also provided extra hydrophilic sites and interfacial compatibility for subsequent Pebax selective layer coating. With the present of PDMS- b -PEO in the intermediate layer, an integrated Pebax selective layer with thickness of ∼50 nm was successfully fabricated. The resulting ultra-thin Pebax composite membrane exhibited outstanding performance with CO 2 permeance of 2142 GPU and CO 2 /N 2 selectivity of 36. The strategy of using amphipathic copolymer as intermediate layer enhanced the composite membrane integrity and simplified the plasma pre-treatment, showing great potential in developing highly permeable membrane for efficient CO 2 capture.
Poor interfacial compatibility that often led to low gas separation performance is one of key challenges for developing composite membranes. In the present study, nanosized polyethyleneimine (PEI) functionalized ZIF-8 (PEI-ZIF-8) with good dispersion, having a particle size around 15 nm, has been synthesized via in-situ method and used as filler to fabricate Pebax/PEI-ZIF-8 composite membranes. Excluding the intrinsic porous structure and higher affinity with CO 2 of PEI-ZIF-8 beneficial for CO 2 selective transport, the large density of amine groups on PEI chains provide a good interfacial compatibility, and introduce facilitated CO 2 transport path. Furthermore, PEI-ZIF-8 reduces the crystallinity of Pebax matrix, which is favorable for CO 2 transport. The composite membrane with 5 wt% PEI-ZIF-8 shows a CO 2 permeance of 13.0 GPU with a CO 2 /N 2 selectivity of 49.0, which increases by 80.6% and 118.8% respectively in contrast with pristine Pebax membrane. The results demonstrate that nanoparticles functionalized by amine-polymer with long chains is effective for constructing composite membranes with good interfacial compatibility.
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