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Separation Properties (separation + property)
Selected AbstractsCinchona Alkaloid,Metal Complexes: Noncovalent Porous Materials with Unique Gas Separation Properties,ANGEWANDTE CHEMIE, Issue 39 2010Prof. Smarte Poren: Zweikernige Aluminium-Cinchonin-Komplexe dienen als Bausteine zur Selbstorganisation chiraler Architekturen mit nichtkovalenten Wechselwirkungen (siehe Bild). Das flexible desolvatisierte Material mit Ultramikroporen ist ein selektives Adsorptionsmittel mit einzigartigen Eigenschaften, z.,B. hohen Affinitäten für H2, CO2 und CH4 und einer temperaturgeregelten Adsorption von N2. [source] Self-Supporting, Double Stimuli-Responsive Porous Membranes From Polystyrene- block -poly(N,N -dimethylaminoethyl methacrylate) Diblock CopolymersADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Felix Schacher Abstract Asymmetric membranes are prepared via the non-solvent-induced phase separation (NIPS) process from a polystyrene- block -poly(N,N -dimethylaminoethyl methacrylate) (PS- b -PDMAEMA) block copolymer. The polymer is prepared via sequential living anionic polymerization. Membrane surface and volume structures are characterized by scanning electron microscopy. Due to their asymmetric character, resulting in a thin separation layer with pores below 100,nm on top and a macroporous volume structure, the membranes are self-supporting. Furthermore, they exhibit a defect-free surface over several 100,µm2. Polystyrene serves as the membrane matrix, whereas the pH- and temperature-sensitive minority block, PDMAEMA, renders the material double stimuli-responsive. Therefore, in terms of water flux, the membranes are able to react on two independently applicable stimuli, pH and temperature. Compared to the conditions where the lowest water flux is obtained, low temperature and pH, activation of both triggers results in a seven-fold permeability increase. The pore size distribution and the separation properties of the obtained membranes were tested through the pH-dependent filtration of silica particles with sizes of 12,100,nm. [source] Fabrication and Characterization of Nanoporous Carbon/Silica Membranes,ADVANCED MATERIALS, Issue 4 2005B. Park Nanoporous carbon/silica (C/SiO2) membranes (see Figure) with high permeabilities and high gas selectivities are prepared by the controlled pyrolysis of polyimide/silica (PI/SiO2) composites obtained from polymerization of alkoxysilanes in situ via a sol,gel reaction. The silica content and the nature of the silica network incorporated in the carbon matrix can be used to tune the gas permeation and separation properties of the final C/SiO2 membranes. [source] Semi-IPN asymmetric membranes based on polyether imide (ULTEM) and polyethylene glycol diacrylate for gaseous separationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Sundar Saimani Abstract Semi-interpenetrating polymer networks (semi-IPN) formed with commercial polyether imide (ULTEM®, PEI) and poly (ethylene glycol) diacrylate (PEGDA) were used to make asymmetric membranes. The effect of increasing amount of PEGDA on the bulk and the gas separation properties of semi-IPN membranes were studied. The formation of IPNs was confirmed by Fourier Transform Infra Red (FT-IR) spectroscopy. The 5% weight loss temperature decreased and the percent weight loss of the first step increased with increase in the PEGDA content, which indicated the incorporation of more poly (ethylene glycol) (PEG) segments to the semi-IPNs. The microscopic experiments revealed the change in morphology with change in PEGDA content. The Scanning electron micrographs exhibited typical finger-like voids in the sub layer, which is characteristic morphology of asymmetric membranes. The increase in PEGDA content up to 5.7 wt % increased the CO2/N2 selectivity of the semi-IPN after which the selectivity decreased and permeance increased. Although, the increase in the polar poly (ethylene glycol) molecules is expected to render better CO2 selectivity, the performance of the membrane was found to decrease as PEGDA content exceeded 5.7% for the given ratio. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] GC separation of amino acid enantiomers via derivatization with heptafluorobutyl chloroformate and Chirasil- L -Val columnJOURNAL OF SEPARATION SCIENCE, JSS, Issue 22 2009Helena Zahradní Abstract Heptafluorobutyl chloroformate (HFBCF), a recently introduced derivatization reagent, was examined in enantioseparation of amino acids (AAs) by GC. Twenty proteinogenic AAs, plus ornithine, cystine and 4-fluorophenylalanine (internal standard) were treated with the reagent and separation properties of the derivatives were assessed on a Chirasil-Val capillary column. Nineteen AA enantiomers were efficiently separated in 43,min except proline, arginine and cystine. The HFBCF derivatives of the studied DL -AAs show improved separation over other chloroformate-based derivatives hitherto reported. A combination of the improved and faster separation with a simple derivatization protocol, involving an immediate one-step reaction,extraction in two-phase aqueous-organic medium, and low elution temperatures extend application of HFBCF to chiral AA analysis. [source] Synthesis and Properties of 6FDA-MDA Copolyimide Membranes: Effects of Diamines and Dianhydrides on Gas Separation and Pervaporation PropertiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 24 2007Shude Xiao Abstract 6FDA-MDA-based polyimides were synthesized from a one-step polycondensation of 6FDA and MDA with other diamines and dianhydrides. The polyimides were characterized by GPC, FT-IR and NMR, and dense membranes were prepared from their solutions for gas separation and pervaporation. Gas separation and pervaporation properties were investigated using the linear moiety contribution method. The moiety contribution factors were used to analyze the effects of the dianhydride and diamine monomers on gas permselectivity and pervaporation permeation flux. It was shown that the steric effects and flexibility of the monomers and the interactions between the membrane and the penetrants accounted for the differences in separation properties. [source] | ||||||||||||||||||||||