Water resistant sulfonated polyimides based on 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (BNTDA) for proton exchange membranes

A series of sulfonated polyimides (SPIs) were synthesized in in-cresol from 4,4'-binaphthyl- 1,11,8,8'-tetracarboxylic dianhydride (BNTDA), 4.4'-diaminodiphenylether-2,2-disulfonicacid (ODADS), and 4.4'-diamino-diphenyl ether (ODA) in the presence of triethylamine and benzoic acid. The resulted polyimides showed much better water resistance than the corresponding sulfonated polyimides from 1,4,5,8-naphthatenetetracarboxylic dianhydride (NTDA) and ODADS, which is contributed to the higher electron density in the carbonyl carbon atoms of BNTDA. Copolyimides S-75 and S-50 maintained their mechanical properties and proton conductivities after aging in water at 100 degrees C for 800 h. The proton conductivity of these SPIs was 0.0250-0.3565 S/cm at 20 degrees C and 100% relative humidity (RH), and increased to 0.11490.9470 S/cm at 80 degrees C and 100% RH. The methanol permeability values of these SPIs were in the range of 0.99-2.36 x 10(-7) cm(2)/S, which are much lower than that of Nafion 117 (2 x 10(-6) cm(2)/s).

New proton exchange membranes based on poly (vinyl alcohol) for DMFCs

A series of new composite proton exchange membranes for direct methanol fuel cells (DMFCs) based on poly (vinyl alcohol) (PVA), phosphotungstic acid (PWA) and silica were prepared. The highest proton conductivity (a) of these membranes is 0.017 S/cm at ambient temperature. The methanol permeability (D) of these composite membranes ranges from 10(-7) to 10(-8) cm(2)/S. From the ratios of sigma/D, it was found that the optimal weight composition of the PVA/PWA/SiO2 membrane is PVA/PWA/SiO2=0.40:0.40:0.20 wt. Infrared (IR) spectrographic measurements indicate that the Keggin structure characteristics of the PW12O403- anion is present in the composite membranes. Cyclic voltammetry shows that the electrochemical stability window of the complex membrane is from -0.5 to 1.5 V vs. Ag/AgCl electrode. The results of differential scanning calorimetry (DSC) show that silica can improve the thermal stability of the complexes and the single Tg of the membrane indicates that the membrane is homogeneous. The complexes behave as X-ray amorphous.

A room-temperature ionic-liquid-templated proton-conducting gelatinous electrolyte

Novel proton-conducting gelatinous electrolytes templated by room-temperature ionic liquid (RTIL) 1-butyl-3-methyl-imidazolium-tetrafluoroborate (BMImBF(4)) have been prepared in methylsisesquioxane backbone containing H3PO4, and the influences of the RTIL on the structure, morphology, thermal stability, and electrochemical properties of the gelatinous electrolytes have been examined. X-ray diffraction and scanning electron microscopy proved that BMImBF(4) acted as structure-directing template during the sol-gel process of methyl-trimethoxysilane. X-ray photoelectron spectra and infrared spectroscopy demonstrated that the hydrogen-bonding was formed between BMImBF(4) and H3PO4. The electrolytes had good thermal stability up to 300 degreesC and showed superior mechanical and electrochemical properties. A room-temperature conductivity of 1.2 x 10(-3) S cm(-1) was obtained for the electrolyte at the molar ratio of RTIL/Si/H3PO4 0.3/1/1, and its electrochemical window was up to 1.5 V.

Sulfonated poly(arylene-co-naphthalimide)s synthesized by copolymerization of primarily sulfonated monomer and fluorinated naphthalimide dichlorides as novel polymers for proton exchange membranes

A novel sulfonated aromatic dichloride monomer was successfully prepared by the reaction of 2, 5-dichlorobenzophenone with fuming sulfuric acid. Copolymerization of this monomer in the form of sodium salt (1) with N-(4-chloro-2-trifluoromethylphenyl)-5-chloro-1,8-naphthalimide (2) or bis(N-(4-chloro-2-trifluoromethylphenyl)1,4,5,8-naphthalimide (3) generated two series of novel poly(arylene-co-naphthalimide) s I-x and II-x where x represents the content of the sulfonated monomer. The synthesized copolymers with the -SO3H group in the side chains possessed high molecular weights revealed by their high viscosity and the formation of tough and flexible membranes. The copolymers exhibited excellent stability toward water and oxidation due to the introduction of the hydrophobic CF3 groups. The sulfonated copolyimides that incorporated with 1,8-naphthalimide (I-x) exhibited better hydrolytic and oxidative stabilities than those with 1,4,5,8-naphthalimide. Copolymer I-50 membrane endured for more than 83 h in Fenton's reagent at room temperature. The mechanical properties of I-50 membrane kept almost unchanged after immersing membrane in boiling water for 196 h. The proton conductivities of copolymer films increased with increasing IEC and temperature, reaching values above 6.8 x 10(-1) S/cm at 80 degrees C.

The direct synthesis of wholly aromatic poly(p-phenylene)s bearing sulfobenzoyl side groups as proton exchange membranes

Sulfonated poly(p-phenylene)s (SPPs) containing sulfonic acid groups in their side chains had been directly synthesized by Ni(0) catalytic coupling of sodium 3-(2,5-dichlorobenzoyl)benzenesulfonate and 2,5-dichlorobenzophenone. The synthesized copolymers possessed high molecular weights revealed by their high viscosity, and the formation of tough and flexible membranes by casting from DMAc solution. The copolymers exhibited excellent oxidative stability and mechanical properties due to their fully aromatic structure extending through the backbone and pendent groups. Transmission electron microscopic (TEM) analysis revealed that these side-chain type SPP membranes have a microphase-separated structure composed of hydrophilic side-chain domains and hydrophobic polyphenylene main chain domains. The proton conductivities of copolymer membranes increased with the increase of IEC and temperature, reaching values above 3.4 x 10(-1) S/cm at 120 degrees C, which are almost 2-3 times higher than that of Nafion 117 at the same measurement conditions. Consequently, these materials proved to be promising as proton exchange membranes.

Relaxation behavior of polymer blends with complex morphologies: Palierne emulsion model for uncompatibilized and compatibilized PP/PA6 blends

This paper deals with the dynamic rheological behavior of polypropylene/polyamide6 (PP/PA6) uncompatibilized blends and those compatibilized with a maleic anhydride grafted PP (PP/PP-g-MAH/PA6). The terminal relaxation times of the blends predicted by the Palierne emulsion model were compared with those obtained from experimental relaxation time spectra. The Palierne model succeeded well in describing PP/PA6 uncompatibilized blends with relatively low dispersed phase contents (10 wt%) and failed doing so for those of which the dispersed contents were high (30 wt%). It also failed for the compatibilized ones, irrespective of the dispersed phase content (10 or 30 wt%) and whether or not interface relaxation was taken into consideration. In the case of the uncompatibilized blend with high dispersed-phase content, interconnections among inclusions of the dispersed phase were responsible for the failure of the Palierne model. As for the compatiblized blends, in addition to particle interconnections, the existence of emulsion-in-emulsion (EE) structures was another factor responsible for the failure of Palieme model.

Blue organic light-emitting diodes based on an oxadiazole-containing organic molecule exhibiting excited state intramolecular proton transfer

A blue organic light-emitting device based on an emissive layer of 2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole (HOXD), which exhibits excited state intramolecular proton transfer (ESIPT), was presented. The device had a luminance efficiency of 0.8 cd/A and a maximum brightness of 870 cd/m(2). Our studies indicate that some EL may originate from the triplet excitation state of the enol form of HOXD.

Evaluation of bioeffects of a long-term administering ChangLe on rat by proton NMR method and biochemical examination

High resolution H-1 nuclear magnetic resonance ( NMR) spectroscopy has been employed to assess long-term toxicological effects of ChangLe (a kind of rare earth complex applied in agriculture). Male Wistar rats were administrated orally with ChangLe at doses of 0, 0.1, 0.2, 2.0, 10 and 20 mg/kg body weight daily, respectively, for 6 months. Urine was collected at-day 30, 60, go and serum samples were taken after 6 months. Many low-molecular weight metabolites were identified by H-1 NMR spectra of rat urine. A decrease in citrate and an increase in ketone bodies, creatinine, DMA, DMG, TMAO, and taurine in the urine of the rats. receiving high doses were found by H-1 NMR spectra. These may mean that high-dosage of ChangLe impairs the specific region of liver and kidney, such as renal tubule and mitochondria. The decrease in citrate and the increase in succinate and alpha-ketoglutarate were attributed to a combination of the inhibition of certain citric acid enzymes, renal tubular acidosis and the abnormal fatty acid catabolism. The information of the renal capillary necrosis could be derived from the increase in DMIA, DMG and TMAO. The increase in taurine was due to hepatic mitochondria dysfunction. The conclusions were supported by the results of biochemical measure. merits and enzymatic assay.

Blue organic light-emitting devices with an oxadiazole-containing emitting layer exhibiting excited state intramolecular proton transfer

We report a blue organic light-emitting device having an emissive layer of 2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole (HOXD), that exhibits excited state intramolecular proton transfer (ESIPT). The device had a luminance efficiency of 0.8 cd/A and a maximum brightness of 870 cd/m(2). Electroluminescence spectra revealed a dominating peak at 450 nm and two additional peaks at 480 and 515 nm with a full width at half maximum of 50 nm. Our studies indicate that some EL may originate from the triplet excitation state of the enol form of HOXD.

Effect of rare earth element on the metabolism in rats by high resolution proton nuclear magnetic resonance spectroscopy

The high-field nuclear magnetic resonance (NMR) spectra can be used for the rapid multicomponent analysis in small amounts of biological fluids. In this paper, the effect of La (NO3)(3) on the rats' metabolism in urine was investigated by H-1 NMR analysis. The experimental groups of wistar rats were injected intraperitoneally with La(NO3)(3) at doses of 0.2, 2.0, 10 and 20mg/kg body weight. The remarkable variation of low molecular weight metabolites in urine has been identified by H-1 NMR spectra, in which dimethylamine, N, N-dimethylglycine, urea, alpha -ketoglutarate, trimethylamine N-oxide, succinate, citrate and amino acids have been suggested as NMR markers for renal damage and ethanol, lactate, taurine as the markers for liver damage. This work may assess its possible use in the early detection of biochemical changes associated with Rare Earth induced kidney and liver dysfunction.

Mechanical relaxation time of comblike polymer electrolyte

Using poly(styrene-co-maleic anhydride) as the backbone and poly(ethylene glycol) methyl ether as side chains,three kinds of comblike polymers of different side chain length were synthesized. The Li-salt complexes and their firms were prepared. The dynamic mechanical properties were investigated. It was found that the main chain was rigid and the side chain was flexible in this comblike polymer system. Based on the time-temperature equivalence principle, a master curve was constructed. By selecting T-alpha as reference temperature, Arrhenius plots of shift factor and iso-free-volume plots were attained. The values of WLF parameters C-1 and C-2 increase with increasing salt concentration. By reference to T-0 = 50 degrees C, the relation between the average relaxation time 1g tau(c) and Li-salt concentration C is linear. The master curves are displaced progressively to higher frequencies as the M-w of side chains is increased. The relation between the average relaxation time 1g tau(n) and M-w of side chains is also linear. And the master curves are movable with the change of salts. It shows the effect of different kinds of salt on relaxation time.

Influence of intermolecular entanglements on the glass transition and structural relaxation behaviors of macromolecules. 2. Polystyrene and phenolphthalein poly(ether sulfone)

The effect of entanglements on the glass transition and structural relaxation behaviors has been studied for polystyrene (PS) and phenolphthalein poly(ether sulfone) (PES-C) samples by fast evaporation of the solution of concentrations varying from above the overlapping concentration to far below it, and compared to the results we have studied previously in PC. It has been found that for all the polymers we have studied, in the concentrated solution region, the T-g of the samples obtained from solution are independent of the change of concentration and are very close to that of normal bulk samples, whereas in the dilute solution region the T-g of the samples decrease with the logarithm of decreasing concentration. The critical concentrations that divide the two distinct regions for the three polymers are 0.9% g/mL for PC, 0.1% g/mL for PS, and 1% g/mL for PES-C. The decrease of T-g of the samples is interpreted by the decrease of intermolecular entanglements as the isolation of polymer chains, and the entanglement of polymer chains restrained the mobility of the segments. The structural relaxation behavior of the polymers is also found to be different from that of normal bulk samples. The enthalpies of single-chain samples are lower than that of the bulk ones, which correspond to the lower glass transition temperature; the peaks are lower and broader, and the relaxed enthalpy is much lower as compared to that of bulk samples. In the three polymers we have studied, the influence of change of entanglements on both the decrease in glass transition temperature and relaxed enthalpy is the most significant for PS and the least for PES-C. It is indicated that the interactions in the flexible polymers are weak; thus, the restraint of the entanglements on the mobility of the segments plays a more important role in the flexible polymers, and the change of entanglement in the flexible polymers has a more significant influence on the physical properties.

Investigation of proton transfer across the water/1,2-dichloroethane interface by o-phenanthroline using glass micro/nano-pipets and cyclic voltammetry

Facilitated proton transfer across the water/1,2-dichloroethane (DCE) interface supported on the tips of micro- and nano-pipets by o-phenanthroline (Phen) was studied by using cyclic voltammetry. The formed micro- and nano-liquid/liquid interfaces functioned as micro- and nano-electrodes under certain experimental conditions. The dependence of the half-wave potentials on the aqueous solutions acidities was studied and the ratio of association constants between Phen and proton in the aqueous and DCE phases was calculated by the method proposed by Matsuda et al.. The standard rate constant (k(0)) and the transfer coefficient (alpha) evaluated by using nano-pipets were equal to 0.183 +/- 0.054 cm/s and 0.70 +/- 0.09, respectively.

Influence of entanglements an the glass transition and structural relaxation behaviors of macromolecules. 1. Polycarbonate

We obtained the single-chain polycarbonate sample, by a new fast evaporation method and found that the polycarbonate sample obtained by this method is completely amorphous, while the polycarbonate sample obtained by other methods all have a certain degree of crystallinity. The glass transition temperature (T-g) of the sample decreases with the decreasing of concentration when the concentration of the prepared solution is below the critical value. The critical concentration we obtained from the T-g dependence of concentration is 0.9% g/mL and is in accord with that obtained by viscometry and light scattering methods directly from the solution. The structural relaxation behavior is found also different from that of a normal bulk sample of polycarbonate. The enthalpic peak of the single-chain sample is lower: than that of the bulk one, which corresponds to the lower glass transition temperature. The peak of the single-chain sample is lower and broader, and the relaxed enthalpy is much lower compared with that of the bulk sample. These results have been explained in terms of the effect of entanglement on the mobility of the segments in polymer and the compact conformation in the single-chain sample.