When complexed with alkaline such as potassium hydroxide, sodium hydroxide or lithium hydroxide, films (40 μm thick) of polybenzimidazole (PBI) show conductivity in the 5 × 10−5–10−1 S/cm−1 range, depending on the type of alkali, the time of immersion in the corresponding base bath and the temperature of immersion. It has been shown that PBI has a remarkable capacity to concentrate KOH, even in an alkaline bath of concentration 3 M. The highest conductivity of KOH-doped PBI (9×10−2 S cm−1) at 25°C obtained in this work is higher than the we had obtained previously as optimum values for H2SO4-doped PBI (5 × 10−2 S cm−1 at 25°C) and H3PO4-doped PBI ( 2 × 10−3 S cm−1 at 25°C). PEMFCs based on an alkali-doped PBI membrane were demonstrated, and their characteristics exhibited the same performance as those of PEMFCs based on Nafion® 117. Their development is currently under active investigation. 相似文献
The deformation of piezoelectric composite has many deadly effects on the transducers and the sonar systems, but the relative testing method never been focused. Here we developed a novel fiber-grating-sensing method for the study of temperature deformation of the piezoelectric composites for the first time. With the increase of temperature, the deformations of the piezoelectric composite in three dimensions increased, and the increasing speeds (all speeds means slop of fitted line) were 1.4 × 10−3 (length), 1.8833 × 10−4 (width) and 3.1439 × 10−5 (thickness), respectively. After adding the deform information the data for the frequency constant and dielectric constant were revised. The decreasing speed of frequency constant lowered from −2.0373 to −2.0263. The increasing speed of dielectric constant lowered from 2.6779 to 2.6580 in the range of 25 °C–75 °C, and from 1.9647 to 1.9559 in the range of 75 °C–125 °C. 相似文献
The temperature dependence of the rate constant for the reactions of HO2 with OH, H, Fe2+ and Cu2+ has been determined using pulse radiolysis technique. The following rate constants, k (dm3 mol−1 s−1) at 20°C and activation energies, Ea (kJ mol−1) have been found. The reaction with OH was studied in the temperature range 20–296°C (k=7.0×109, Ea=7.4) and the reaction with H in the temperature range 5–149°C (k=8.5×109, Ea=17.5). The reaction with Fe2+ was studied in the temperature range 16–118°C (k=7.9×105, Ea=36.8) and the reaction with Cu2+ in the temperature range 17–211°C (k=1.1×108, Ea=14.9). 相似文献
A new diimide-diacid, (4-(4-(2,6-diphenylpyridin-4yl)phenoxy)phenyl)-1,3-bis(trimellitimidobenzene) (PPMIB), was synthesized from the condensation reaction of a new diamine, (4-(4-(2,6-diphenylpyridin-4yl)phenoxy)phenyl)-3,5-diaminobezamide (PPDA), and trimellitic anhydride carboxylic acid (TMAA) in glacial acetic acid. The diimide-diacid (PPMIB) was characterized by FT-IR, 1H-NMR and elemental analysis. A series of novel aromatic poly(amide-imide)s (PAIs) was synthesized by using direct polycondensation of PPMIB with various diamines in NMP in the presence of triphenylposphite and pyridine as condensing agents. The resulting PAIs were amorphous, readily soluble in many polar aprotic solvents and showed inherent viscosities of 0.35–0.50 dL/g. According to thermal analysis, these polymers exhibited glass transition temperatures (Tgs) in the range of 202–280°C and temperature of 10% weight loss (T10) varied from 400 to 545°C in N2. These polymers in NMP solution exhibited strong UV-Vis absorption maxima at 320°C nm and their fluorescence emission peaks appeared around 410–565 nm. 相似文献
A potentiometric sensor modified with a nanocomposite of montmorillonite sheets decorated with polyaniline nanofibers (MT-PANI-NFs) as an efficient electroactive material and tricresyl phosphate (TCP) as a solvent mediator has been developed for the estimation of clomipramine HCl (CLP.HCl). The optimum potentiometric performance of the sensor was achieved by mixing of MT-PANI-NFs : TCP : graphene with a ratio of 2.69 : 30.11 : 67.20 (% wt/wt). The sensor exhibited a Nernstian slope of 59.0±0.1 mV decade−1 over the concentration range of 1.0×10−5−1.0×10−2 mol L−1 with a theoretically calculated detection limit of 5.0×10−6 mol L−1. The sensor performance was scrutinized in terms of several factors including thermal stability, pH effect, response time and selectivity. As, it displayed a high thermal stability at various temperature degrees (10–60 °C) with pH independency in the range of 3.5–8.5. Additionally, the developed sensor exhibited a very rapid performance for CLP.HCl detection with a fast response time of 4 s and reflecting a superior selectivity towards CLP.HCl over the other interfering species. SEM (scanning electron microscope) was used as a characteristic tool for the investigation of the proposed graphene sensor surface. Furthermore, the graphene sensor has been efficiently used for CLP.HCl estimation in its pharmaceutical formulations. 相似文献
1, 4-Bis(4-aminophenoxy)-2-tert-butylbenzene was synthesized and used as a monomer to prepare a series of polyamides by the direct polycondensation with various aromatic dicarboxylic acids in N-methyl-2-pyrrolidone using triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.75–1.75 dL g−1. All the polyamides showed amorphous nature and most of them were soluble in polar solvents. Polyamides derived from 4, 4'-sulfonyldibenzoic acid and 4, 4'-hexafluoroisopropylidenedibenzoic acid were even soluble in common organic solvent such as THF. All polyamide films could be obtained by casting from their DMAc or NMP solutions. The polyamide films had a tensile strength range of 35–84 MPa, an elongation range at break of 3–7%, and a tensile modulus range of 1.2–2.5 GPa. These polyamides had glass transition temperatures between 203–268°C and 10% mass loss temperatures were recorded in the range of 456–472°C in nitrogen and 453–470°C in air atmosphere. 相似文献
Metathesis cyclopolymerization of mono‐ or bissubstituted 1,6‐heptadiynes is undergone to generate the ionic polyacetylenes (iPAs) with branched 1,2,3‐ttriazolium pendants, which possess relatively high intrinsic ionic conductivities of 1.4 × 10−5–2.1 × 10−5 S cm−1 at 30 °C. The doping treatment with lithium bis(trifluoromethanesulfonyl)imide endows iPAs with enhanced ionic conductivities of 2.5 × 10−5–4.3 × 10−5 S cm−1. Further doping with iodine, iPAs show ionic and electronic dual conductivities of 4.5 × 10−5–7.1 × 10−4 and 1.5 × 10−6–4.5 × 10−6 S cm−1, respectively. Therefore, the doped iPAs demonstrate the potential in the area of conducting polymers and polymeric electronics.
New aromatic poly(amide-imide)s with high inherent viscosities were prepared by direct polycondensation reaction of diimide-diacid (I) and aromatic diamines using triphenyl phosphite in N-methyl-2-pyrrolidone (NMP)/pyridine solution containing dissolved CaCl2. The bis(3-trimellitimidophenyl) phenyl phosphine oxide (I) was readily obtained by the condensation reaction of bis(3-aminophenyl) phenyl phosphine oxide (BAPPO) with trimellitic anhydride. The resulting poly(amide-imide)s showed high thermostability. Their decomposition temperatures at 10% weight loss in nitrogen atmosphere were above 532 °C and the anaerobic char yield at 800 °C ranged from 56% to 74%. Almost all the poly(amide-imide)s showed high glass transition temperature above 233 °C by differential scanning calorimetry (DSC) measurements. These polymers were readily soluble in various organic solvents and by their casting into transparent, tough and flexible films can be easily achieved. 相似文献