ABSTRACT This paper describes preparation and physico-chemical properties of 1-alkoxy-4-(2-perfluoroalkyl)ethoxybenzenes (FmOOCn). For FmOOCn, 4-F(CF2)mCH2CH2O-phenyl-O-(CH2)nH, three homologues, m = 8 (n = 1, 2) and m = 10 (n = 1) reveal monotropic smectic A and unidentified smectic phases, respectively. Simultaneously, most of the homologous are possible to gelatinize various organic solvents such as octane, cyclohexane, DMF, ethanol, and so on. The gelation ability increases with increasing the carbon number of the perfluoroalkyl chain. The formed gel is transparent, semitransparent or opaque, and the phase transition between the gel phase and the isotropic fluid is thermally reversible. The images of gel observed with scanning electron microscope (SEM) show gathered fibrous aggregates.
Abstract Homologous series of 2-oxochromen-6-yl 4-alkoxybenzoates (1-n, n = 2–10) and 4-alkoxybiphenyl-4′-carboxylates (2-n, n = 5–8) can gelate various organic solvents, where the gel–sol transition temperatures are ca. 60 and 90 °C, respectively.
Permeability, solubility and diffusion coefficients [P, S, and _??_ (=P/S)] of gases were measured at 35°C and 10 atm for a series of polyimides prepared from four acid dianhydrides and three diamines. The introduction of CF3 groups decreased the packing density of polymer segments, resulting in a small increase in S and large increases in _??_ and P. A roughly linear relationship was observed between In _??_CO2 and the inverse of the fraction of "free space" (or expansion volume). The diffusivity selectivity was significantly different among the polyimides, while the solubility selectivity changed only slightly. For the CO2/CH4 system, polyimides having lower local segmental mobility tended to have higher diffusivity selectivity. The introduction of -C(CF3)2- linkages and/or CF3 substituent groups was effective for CO2/CH4 and O2/N2 separations, but not for H2/CO and H2/CH4 separations, because in the latter cases a moderate increase in PH2 was followed by significant decreases in PH2/PCO and PH2/PCH4.
Vapor-permeation (VP) aided esterification of oleic acid with ethanol and methanol was carried out at 383 K using both a pressurized vapor circulation system and a laboratory module of Zeolite membrane with excellent VP performance of dehydration of organic liquids. The combined process provided almost complete conversion in a short reaction time with the initial molar ratio of alcohol to oleic acid (m0) of 1.5. The reaction time, as for ethanol, was reduced by a factor of 1/3 as compared with the process carried out under the atmospheric pressure using a laboratory module of polyimide hollow fiber. The loss of alcohol by permeation was below 0.01% of the feed for ethanol and was only 0.16% for methanol. This indicates that the almost complete reaction can be achieved even if m0 goes down to unity. The Zeolite membrane worked effectively and stably for a long period, and is useful for achieving the highly efficient process of esterification.
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