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Compared to polysulfone (PSF), the effects of chemical structure on gas separation performance of polyethersulfone (PES) are rarely in-depth studied. To explore the potential of various PES polymers as gas separation membranes, PES containing four different backbone structures have been synthesized. They are polyphenylsulfone (PPSU), poly trimethyl benzene ethersulfone (TPESU), polyethersulfone (PESU)...
Polyphenylenesulfone (PPSU) is widely used as a membrane material for water reuse applications because of its good chemical resistance, hydrolysis stability and outstanding mechanical strength. However, due to its hydrophobic nature, fouling and relatively low water permeability are potential drawbacks of PPSU membranes. Sulfonation of PPSU could significantly improve the hydrophilicity but compromise...
Physical aging in high free volume polymers reduces gas permeability which limits their potential for gas separation. Plasticization is another concern when the separation involves a highly condensable gas such as CO2 or operates in aggressive conditions. This work reports a straightforward strategy to suppress aging and plasticization of polymers of intrinsic microporosity, specifically PIM-1, with...
Miscible blends of Matrimid and carboxylated polymers of intrinsic microporosity (cPIM-1) at the molecular level have been discovered. Their miscibility has been confirmed by polarized light microscopy (PLM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The existence of hydrogen bonding promotes...
Fundamental transport properties including salt and water partition coefficients, permeability and diffusivity of various newly synthesized cellulose esters were evaluated in this study in order to investigate the relationship among them as a function of molecular structure. Dense flat cellulose ester films were prepared and studied so that the influence of membrane fabrication, morphology and processing...
The effects of nitrogen and air purge during thermal rearrangement of an ortho-functional polyamide (o-PA) and an ortho-functional polyimide (o-PI) towards a polybenzoxazole (PBO) structure have been investigated in terms of physicochemical changes and gas transport properties. The o-PA polymer was prepared from 2,2-bis(3-amino-4-hydroxyphenyl) hexafluropropane (BisAPAF) and 4,4′-biphenyl-dicarbonyl...
We have studied alcohol- and water-induced swelling and sorption of PBI and PBI/ZIF-8 nano-composite membranes and characterized both dry and wet membranes by positron annihilation lifetime spectroscopy (PALS). The degrees of membrane swelling after immersing in alcohols and water follow the order of ethanol > methanol > water > n-butanol. Addition of ZIF-8 particles into PBI membranes suppresses...
The fundamental salt and water transport properties of cellulose ester polymers have been studied and correlated with their hydrated free volume, as probed by positron annihilation lifetime spectroscopy (PALS), to provide scientific insights for material development in seawater desalination. It has been found that the hydrated free volume is strongly dependent on water uptake. The water sorption in...
Industrial gas separation membranes have selective dense layers with thicknesses around 100 nm. It has long been assumed that these thin layers have the same properties as thick (bulk) films. However, recent research has shown that thin films with such thickness experience accelerated physical aging relative to bulk films and, thus, their permeation properties can differ significantly from the bulk...
Organic-inorganic materials comprising CO 2 -philic components may yield superior CO 2 transport properties and good CO 2 /H 2 gas selectivity. We report that a fine balance in size heterogeneity in the silicon-based structures is essential and a mixture of sizes up to 50 nm surrounded by 5–15 nm silicon-based nanostructures is the preferred inorganic phase morphology...
The thermally induced structure transformation and polymer chain rearrangement of a thermally rearranged (TR) material for gas separation has been explored in this work. A tremendous enhancement as high as 215 folds in CO 2 permeability has been achieved by converting the pristine poly(hydroxyamide amic acid) (PHAA) to the final polybenzoxazole (PBO) via thermal cyclization at 400 °C for 2 h...
Experimental measurements and fully atomistic simulations are carried out to examine the CO 2 -induced plasticization of a polyimide membrane synthesized from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 4,4′-oxydianiline (ODA). With increasing feed pressure, the permeability of CO 2 in the 6FDA-ODA membrane initially decreases, crosses a minimum, and then increases...
Reverse selective membranes comprising poly(ethylene oxide) (PEO) containing copolyimides (PEO-PI) with variations of acid dianhydrides and diamines have been synthesized for hydrogen purification. The reverse selectivity of the membranes decimate the energy required for hydrogen recompression process. Factors including PEO content, PEO molecular weight, and fractional free volume (FFV) that would...
The integration of molecular design with diamine modification generates synergistic effects for enhancing and fine tuning the molecular sieving potential of polyimide membranes. Polymer free volume and rigidity represent crucial conformational parameters that influence the effectiveness of diamine modification for elevating the H 2 /CO 2 permselectivity of polyimide membranes. Experimental...
We have investigated the macromolecular structure and rheological behavior of both linear and hyperbranched polyethersulfone (PES) materials. It was found that the hyperbranched PES material has a higher molecular weight and a wider molecular weight distribution than its linear analogue. Rheological studies disclose that polymer solutions made from the HPES/polyvinylpyrrolidone (PVP)/N-methyl-2-pyrrolidone...
This study demonstrates the successful implications of blending technique cum chemical modification for the fabrication of high performance polymeric membranes for gas separation applications. The effect of variation in composition on miscibility and microstructure, gas permeability and selectivity of blend membranes is investigated. It is found that augmentation in PBI composition results in enhancement...
We have discovered two new miscible polymer blend systems, namely, Torlon ® 4000T with Matrimid ® 5218 and Torlon 4000T with polybenzimidazole (PBI). Both Matrimid 5218 and PBI are miscible at a molecular level with Torlon 4000T over the whole composition range as confirmed by microscopy, DSC, FTIR and DMA. DSC and DMA studies show the existence of a single glass transition in each...
In this study, wholly aromatic main chain copoly(ester–amide)s containing tetrafluorophthalic acid (TFPA-ortho), tetrafluoroisophthalic acid (TFIA-meta) and tetrafluoroterephthalic acid (TFTA-para) were synthesized to study the effects of kinks on the formation of mesophase and crystal texture. The effects of kink moieties on these copoly(ester–amide)s were also investigated by the ‘RIS’ metropolis...
Cyclic threading/dethreading of novel polypseudorotaxane obtained from β-cyclodextrins and poly(amino ester), poly(BDA–DEEDA), obtained from the Michael addition polymerization of 1,4-butanediol diacrylate (BDA) and N, N′-diethyl ethylenediamine (DEEDA), was realized by adjusting pH of the aqueous solutions between ca. 9.0 and 3.2 alternatively. 1 H NMR, XRD profiles, and 13 C CP/MAS...
We have identified the effect of a fluorine lateral moiety on the liquid crystallinity of wholly aromatic polyester-amides. The evolution of liquid crystal texture for two reaction systems, p-acetoxybenzoic acid (ABA)/acetoxy acetanilide (AAA)/3-fluorophthalic acid (FPA) and ABA/AAA/phthalic acid (PA), were examined and compared by in situ polymerizations under a polarizing microscope with a heating-stage...
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