Radiation-Induced Emulsion Copolymerization of Tetrafluorethylene with Propylene. The Behavior of the HF Formed

The radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene was carried out at room temperature in the presence of gaseous monomers. The formation of hydrofluoric acid in the course of polymerization was observed. The amount of HF formed increased linearly with the irradiation time at various dose rates in the early stage. The tendency was similar to that of time-polymer yield curves. The rate of HF formation was proportional to the first order of the dose rate. The amount of HF formed increased in the presence of oxygen and decreased remarkably above 1 wt% emulsifier, while the polymer yield decreased in the presence of oxygen and increased with the emulsifier concentration. A remarkable decrease in the amount of HF formed in higher emulsifier concentration is mainly attributable to chemical absorption or electrostatic capture of H⁺ ion on polymer particles produced. Hydrofluoric acid is mainly formed by reaction between primary products (e _aq ^? and H) from the radiolysis of water and organic fluoride (tetrafluoroethylene and emulsifier), and is little formed by reaction between primary products and copolymer produced. The G value of HF formation was in the order of emulsifier-water system > suspension polymerization > emulsion polymerization, while the polymer yield was in the order of emulsion polymerization > suspension polymerization.     

Phase behavior of binary bilayer membrane of dipalmitoylphosphatidylcholine and stigmasterol

Journal of Thermal Analysis and Calorimetry - We investigated the phase behavior of a binary bilayer membrane of dipalmitoylphosphatidylcholine (DPPC) and stigmasterol (Stig) as a function of the...     

Salt effect on bilayer phase transitions of dipalmitoylphosphatidylglycerol in saline water under high pressure

ABSTRACT

The phase transitions of dipalmitoylphosphatidylglycerol (DPPG) bilayer membrane at high NaCl concentrations under high pressure were investigated to construct the temperature–pressure phase diagram and to determine phase-transition properties. The constructed phase diagrams exhibited qualitative resemblance to that of the dipalmitoylphosphatidylcholine (DPPC) bilayer membrane: they showed the gel-phase polymorphism including the pressure-induced bilayer interdigitation. The phase-transition properties of the DPPG bilayer membrane changed in a salt concentration-dependent manner. We discussed the salt effect on the DPPG bilayer membrane from the variation in interactions between the polar head groups of the PG molecules.     

强碱阴离子交换树脂及碱性洗脱剂的离子排阻/阴离子交换色谱法同时测定NH4+ ，NO2-和NO3-（英文）

Ion-exclusion/anion-exchange chromatography(IEC/AEC) on a combination of a strongly basic anion-exchange resin in the OH——form with basic eluent has been developed.The separation mechanism is based on the ion-exclusion/penetration effect for cations and the anion-exchange effect for anions to anion-exchange resin phase.This system is useful for simultaneous separation and determination of ammonium ion(NH+4),nitrite ion(NO-2),and nitrate ion(NO-3) in water samples.The resolution of analyte ions can be manipulated by changing the concentration of base in eluent on a polystyrene-divinylbenzene based strongly basic anion-exchange resin column.In this study,several separation columns,which consisted of different particle sizes,different functional groups and different anion-exchange capacities,were compared.As the results,the separation column with the smaller anion-exchange capacity(TSKgel Super IC-Anion) showed well-resolved separation of cations and anions.In the optimization of the basic eluent,lithium hydroxide(LiOH) was used as the eluent and the optimal concentration was concluded to be 2 mmol/L,considering the resolution of analyte ions and the whole retention times.In the optimal conditions,the relative standard deviations of the peak areas and the retention times of NH+4,NO-2,and NO-3 ranged 1.28%-3.57% and 0.54%-1.55%,respectively.The limits of detection at signal-to-noise of 3 were 4.10 μmol/L for NH+4,1.87 μmol/L for NO-2 and 2.83 μmol/L for NO-3.     

离子排斥色谱结合光度检测的水质监测系统用于测定离子型营养物（英文）

A unified ion-exclusion chromatography(IEC) system for monitoring anionic and cationic nutrients like NH + 4,NO 2,NO 3,phosphate ion,silicate ion and HCO 3 was developed and applied to several environmental waters.The IEC system consisted of four IEC methodologies,including the IEC with ultraviolet(UV) detection at 210 nm for determining NH + 4 on anion-exchange separation column in OH form connected with anion-exchange UV-conversion column in I form in tandem,the IEC with UV-detection at 210 nm for determining simultaneously NO 2 and NO 3 on cation-exchange separation column in H + form,the IEC with UV-detection at 210 nm for determining HCO 3 on cation-exchange separation column in H + form connected with anion-exchange UV-conversion column in I form in tandem,and the IEC with visible-detection based on molybdenum-blue reaction for determining simultaneously silicate and phosphate ions on cation-exchange separation column in H + form.These IEC systems were combined through three manually-driven 6-port column selection valves to select each separation column to determine selectively the ionic nutrients.Using this sequential water quality monitoring system,the analytical performances such as calibration linearity,reproducibility,detection limit and recovery were also tested under the optimized chromatographic conditions.This novel water quality monitoring system has been applied successfully for the determination of the ionic eutrophication components in sub-urban river waters.     

Barotropic phase transition between the lamellar liquid crystal phase and the inverted hexagonal phase of dioleoylphosphatidylethanolamine

The phase transition between the lamellar liquid crystal (Lalpha) phase and the inverted hexagonal (H(II)) phase of dioleoylphosphatidylethanolamine (DOPE) in aqueous NaCl solutions was observed by means of differential scanning calorimetry (DSC) under ambient pressure and light-transmittance technique under high pressure. The pressure dependence of the transition temperature (dT/dp) and the thermodynamic quantities for the Lalpha/H(II) transition were compared with those of another phase transition found in the DOPE bilayer membrane, which is the transition from the lamellar crystal (Lc) phase to the Lalpha phase. The dT/dp value of the Lalpha/H(II) transition was about 3.5 times as large as that of the Lc/Lalpha transition while the thermodynamic quantities were significantly smaller than those of the latter to the contrary. Comparing the enthalpy and volume behavior of the Lalpha/H(II) transition with that of the Lc/Lalpha transition, we concluded that the Lalpha/H(II) transition can be regarded as the volume-controlled transition for the reconstruction of molecular packing.     

Dehydro[12]- and -[18]annulenes fused with tetrafluorobenzene: synthesis,electronic properties,packing structures,and reactivity in the solid state

Dehydro[12]- and -[18]annulenes 3 and 4 fused with tetrafluorobenzene were newly synthesized by the copper-mediated oxidative coupling of 1,2-diethynyltetrafluorobenzene. The UV-vis spectra of 3 and 4 showed the maximum absorption to be almost identical to that of the corresponding unsubstituted benzodehydro[12]- and -[18]annulenes 1 and 2, respectively, while the reduction waves in cyclic voltammetry observed at potentials of -1.48 and -1.56 V vs Fc/Fc(+) for 3 and 4 were less negative than those for 1 and 2. In agreement with these results, theoretical calculations (B3LYP/6-31G(d)) indicated that the HOMO-LUMO gap is similar for 1 and 3 and for 2 and 4 but that the LUMO levels of 3 and 4 are apparently lowered by the electronegative fluorine substituents. The X-ray crystallography of single crystals grown from 3 (crystal A), 3.C(6)H(6) (crystal B), and a mixture of 1 and 3 (crystal C) demonstrated that the molecules of 3 are stacked in a slanted manner in crystals A and B, while those of 1 and 3 form sandwichlike 1:2 complexes (3.1.3) that are stacked in a columnar arrangement in crystal C. Despite the suitable packing for topochemical polymerization, crystals A-C were quite stable against photochemical reaction. In contrast, differential scanning calorimetry showed that the thermal polymerization occurred explosively at 120-135 degrees C.     

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene. IV. Effects of emulsifier concentration and dose rate

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene was carried out by batch operation with an initial molar ratio of tetrafluoroethylene to propylene of 3.0 in the emulsifier concentration range of 0.1 to 3.0% and in the dose rate range of 2 × 10⁴ to 2 × 10⁵ R/hr. The effects of emulsifier concentration and dose rate on the polymerization rate and the number-average degree of polymerization are discussed in comparison with the Smith-Ewart theory. The polymerization rate is proportional to the 0.26 power of emulsifier concentration and to the 0.7 power of dose rate. The degree of polymerization is independent of the emulsifier concentration and the dose rate above the critical micelle concentration (CMC) of the emulsifier. These results are not in agreement with the Smith-Ewart theory. It is explained that the termination reaction is a degradative chain transfer of propagating radicals to propylene. On the other hand, the copolymerization in emulsion occurs either below the CMC or in the absence of emulsifier. Under these conditions, however, it is impossible to obtain a copolymer of high molecular weight at a high rate of polymerization because of the presence of a small number of polymer particles formed and the short interval of chain growth in the polymer particle.     

Contribution of the photo-Fenton reaction to hydroxyl radical formation rates in river and rain water samples.

The hydroxyl radical (OH radical) formation rates from the photo-Fenton reaction in river and rain water samples were determined by using deferoxamine mesylate (DFOM), which makes a stable and strong complex with Fe(III), resulting in a suppression of the photo-Fenton reaction. The difference between the OH radical formation rates with and without added DFOM denotes the rate from the photo-Fenton reaction. The photoformation rates from the photo-Fenton reaction were in the range of 0.7 - 45.8 x 10(-12) and 2.7 - 32.3 x 10(-12) M s(-1) in river and rain water samples, respectively. A strong positive correlation between the OH radical formation rate from the photo-Fenton reaction and the amount of fluorescent matter in river water suggests that fluorescent matter, such as humic substances, plays an important role in the photo-Fenton reaction. In rain water, direct photolysis of hydrogen peroxide was an important source of OH radicals as well as the photo-Fenton reaction. The contributions of the photo-Fenton reaction to the OH radical photoformation rates in river and rain water samples were in the ranges of 2 - 29 and 5 - 38%, respectively. Taking into account the photo-Fenton reaction, 33 - 110 (mean: 80) and 42 - 110 (mean: 84)% of OH radical sources in river and rain water samples, respectively, collected in Hiroshima prefecture were elucidated.