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The incorporation of solid fillers into mixed matrix membranes (MMMs) is a promising approach to overcome the permeability-selectivity trade-off characteristic of polymeric membranes. However, MMMs that contain conventional fillers (e.g., zeolites, silicas, and porous carbons) usually exhibit defects due to incompatible interfaces between fillers and glassy polymers. High porosity and good robustness are also desirable properties of filler materials that enhance the gas separation performance of resulting MMMs. Herein, amine-functionalized organic porous polymers (PP-DETA and PP-menm) were synthesized and used as filler materials to yield mechanically stable MMMs that possess good CO2/CH4 separation performance. We found that in comparison with the MMMs loaded with bare porous polymers (PP), composite membranes that contain amine-functionalized fillers exhibited both superior mechanical strength and more effective adhesion to glassy Matrimid® Polyimide (PI) and polysulfone (PSf) polymers. In particular, the tensile strength of 10 wt%_PP-menm@PI was measured to be 69 MPa, which was higher than 26 MPa and 33 MPa for 10 wt%_PP@PI and pure PI membrane, respectively. More importantly, both the CO2 permeability and CO2/CH4 selectivity of MMMs improved significantly after the introduction of amine-functionalized fillers. These results imply that organic porous polymers, particularly those that contain amine-functional groups, are outstanding filler materials for the fabrication of defect-free MMMs with enhanced gas separation performance.

A series of poly(arylene ether sulfone) containing bulky imidazole groups (PSf-Im-x) have been successfully synthesized based on a novel monomer 2,2′-bis-(2-ethyl-4-methyl-imidazole-1-ylmethyl)-biphenyl-4,4′-diol (EMIPO). After quaternized by n-bromobutane, these polymers are evaluated for alkaline anion exchange membranes (AEMs). The functional group, 2-ethyl-3-butyl-4-methyl-imidazolium, is employed in these new polymers for reason that attaching bulky groups around the imidazolium ring reduces the access of OH− to imidazolium, which enhances the alkaline stability of the membranes. The membrane with an IEC value of 2.07 possesses ionic (OH−) conductivity of 0.014 S cm−1 at 30 °C and 80% of the ionic conductivity is maintained after treatment in 1 M KOH at 60 °C for 144 h.

A novel positively charged thin film composite nanofiltration (NF) membrane comprising a nanoporous hyper-crosslinked polyamide barrier layer has been developed by utilizing the highly functional 2,2',4,4',6,6'-biphenyl hexaacyl chloride (BHAC) monomer bearing a rigid and contorted biphenyl skeleton which undergoes interfacial polymerization with piperazine (PIP) on a polyacrylonitrile (PAN) support membrane. The physicochemical properties of the corresponding BHAC-PIP barrier layer were characterized with respect to chemical structure, surface charge performance, morphology as well as film thickness. Moreover, the NF properties studied revealed that the optimized BHAC-PIP composite membrane having a mean effective pore radius of 0.44 nm and molecular weight cut off (MWCO) of 570 Da exhibits high efficiencies for many NE applications including rejection of divalent cations, removal of basic dyes and selective separation of mixed cations. More importantly, the developed BHAC-PIP composite membrane shows higher pure water permeability of 15.3 lm(-2) h(-1) bar when compared with a number of previously reported positively charged NE membranes, the common trimesoyl chloride (TMC)-PIP membrane, as well as our previously developed 3,3',5,5'-biphenyl tetraacyl chloride (BTEC)-PIP NE membranes. Furthermore, comparative studies on the porous properties of the three unsupported BHAC-PIP, BTEC-PIP and TMC-PIP polyamides measured by means of gas sorption experiments indicate the greater porosity of the hyper-crosslinkecl BHAC-PIP polyamide matrix, which is believed to give rise to the highly permeable feature of the resultant BHAC-PIP polyamide barrier layer. This study may provide useful insights for the molecular-level design of NF membrane materials with improved water permeability. (C) 2013 Elsevier B.V. All rights reserved.