Gas separation properties of new polyoxadiazole and polytriazole membranes

Abstract

results in a polymer with a low permeability but an extremely high selectivity. While the permeabilities vary over four orders of magnitude, the solubility remains almost constant and, therefore, the increase in permeability is mainly due to an increase in diffusivity. The permeability is discussed in terms of the polymer free volume.

Gas permeability and permselectivity of polyimides prepared from phenylenediamines with methyl substitution at the ortho position

“…The FFV of PMDA-3MPDA may not give a true picture of its matrix openness, which may be ascribed to the somewhat arbitrary nature of the factor 1.3 in eqn (2), and errors in the group-contribution values. 13,14 The (CH 3 CF 3 ) d in 6FDA-3MPDA is the highest in the polyimides prepared from 3MPDA, which is attributed to two CF 3 groups in 6FDA. The T g of 6FDA-3MPDA, which is similar to that of polyimides prepared from other kinds of dianhydrides with two phenyl units, indicates that the CF 3 group does not increase the chain rigidity of polyimides.…”

Novel polyoxadiazoles with non-coplanar ortho-linked structures as highly CO2 permselective membranes

“…As shown, the gas separation performances of all membranes are below the current Robeson's upper bound. The polyoxadiazole membranes demonstrated almost higher selectivity and in some cases even better CO 2 permeability in comparison to the previously reported polyoxadiazoles 26,27 and polyhydantoins 29 containing materials. This is coupled with their much higher solubility (as they are soluble in polar aprotic solvents) and therefore better processability than that of previously reported polyoxadiazoles.…”

“…8 Comparison of CO 2 /CH 4 selectivity vs. CO 2 permeability of synthesized membranes with some recently important published data including PES and PES-SDS, 48 PES-AS, 54 cellulose-acetate, 55 polyimides and related composite, 56 Matrimide, 57 brominated Matrimid, 58 poly(benzoxazole-co-imide)s, 59 ionic liquid based copolyimide, 60 thermally rearranged PI, 61 PI with bulky group, 18 polyhydantoins (PHYs), 29 and some previously reported polyoxadiazoles shown by triangle. 26,27 This journal is © The Royal Society of Chemistry 2014…”

“…Thermally stable and chemically resistant heteroaromatic polymers such as polyoxadiazoles (PODs) and polyhydantoins have been utilized to prepare dense membranes for CO 2 separation since 1994. [26][27][28][29] Despite their excellent thermal and chemical stabilities and good mechanical properties complemented by high selectivity and good permeability, application of POD membranes in separation technologies were limited by their quite difficult processing and fabrication. Similar to other aromatic rigid polymers, these fully aromatic backbones are not soluble in any organic solvents and exhibit a very high (or no) glass transition temperature.…”

Development of polyimide membranes for the separation of water vapor from organic compounds

“…The tailor-made polyimide membranes based on 2,2Ј-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride (6FDA) were reported to exhibit both higher permeabilities and selectivities than those of many other glassy polymers. 7,8 However, when water vapor is one of the components of gas mixtures, the structure-property relationships of membranes become very complicated, given that water molecules may interact with the polymer to act as a plasticizer or with other water molecules to form clusters. 9 Although 6FDA-based polyimide membranes show good gas separation properties, they are not necessarily good for water and water vapor separation because of their typically hydrophobic properties.…”