Thermal degradation mechanism of poly(arylene sulfone)s by stepwise Py‐GC/MS

The thermal degradation of poly(ether sulfone) (PES) and polysulfone (PSF) was studied with a combination of thermogravimetric analysis and stepwise pyrolysis–gas chromatography/mass spectrometry techniques with consecutive heating of the samples at fixed temperature intervals (100 °C) to achieve narrow‐temperature pyrolysis conditions. The individual mass chromatograms of various pyrolysates were correlated with pyrolysis temperatures to elucidate the pyrolysis mechanism. The major mechanism for both PES and PSF was a one‐stage pyrolysis involving main‐chain random scission and carbonization. The major products SO₂ and phenol were released from the sulfone and ether groups in PES. The major products SO₂, phenol, and 1‐methyl‐4‐phenoxybenzene were released from the sulfone, ether, and isopropylene groups in PSF. In the PES, the thermal stability of the sulfone and ether groups was identical to the maximum thermogravimetric loss rate. In the PSF, the thermal stability was in the following order: sulfone < ether < isopropylene. The temperature of the maximum thermogravimetric loss rate was similar to the maximum evolution of phenol. However, there was a considerable difference in the thermal behavior of both polymers; the correlation of the polymer structure to the degradation mechanism is discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 583–593, 2000     

聚醚砜的磺化及表征

磺化是芳环聚合物改性的有效方法．引入的磺酸基以酸型、盐型和酯型存在,且可以继续制备其它衍生物．有关聚苯醚［１,２］、聚苯硫醚［３］、聚醚醚酮［４,５］和聚砜［６～８］的磺化研究和表征已有很多报道,这些聚合物引入磺酸基后亲水性增强,广泛用于制备反渗透膜...     

聚乙二醇对聚醚砜超滤膜微结构和性能的影响

通过改变铸膜液中添加剂PEG的含量，测试了当铸膜液中PES的质量分数为0．21，凝固浴(DM—SO／H2O体系)中DMSO的质量分数为0．10时，所成膜的水通量和尿素、肌酐去除率。研究了PES／DMSO体系中小分子添加剂PEG作用的规律。     

Basis set effects on the energy and hardness profiles of the hydrogen fluoride dimer

In earlier work, the present authors have shown that hardness profiles are less dependent on the level of calculation than energy profiles for potential energy surfaces (PESs) having pathological behaviors. At variance with energy profiles, hardness profiles always show the correct number of stationary points. This characteristic has been used to indicate the existence of spurious stationary points on the PESs. In the present work, we apply this methodology to the hydrogen fluoride dimer, a classical difficult case for the density functional theory methods.     

HFSiS构型及其稳定性的理论研究

The structures and stability of triplet HFSiS system were investigated by density functional theory（DFT）in detail. The optimized geometrical parameters and vibrational frequencies of all species were obtained at the level of B3LYP/6-311G** and the assignments of them were performed. At the same theoretical level, IRC calculations were carried. In addition, the singlet-point energies and relative energies were calculated by high level electron-correlation CCSD（T）/6-311G**. The isomerized and dissociated processes were explained by vibrational mode analysis method. The triplet PES is compared to the singlet one. The results are as the following: there are six isomers on the triplet PES. Moreover, 3HFSiS is found to be the most thermodynamically and kinetically stable and is able to be observed in experiments. Structures 2 are the more stable ones between the two group bond cycled isomers and are predicted to be detected. 3SiSHF is the most unstable isomer in thermodynamics and kinetics.     

新型燃料电池质子交换膜──含叔丁基的磺化聚芳醚砜

以3,3'-二磺酸钠基-4,4'-二氯二苯砜(SDCDPS)、叔丁基对苯二酚(TBHQ)、二氟二苯酮(DFBP)为原料,利用亲核缩聚反应,通过调整磺化单体(SDCDPS)和非磺化单体(DFBP)的比例与叔丁基对苯二酚(TBHQ)共聚,合成了不同磺化度的聚芳醚砜.聚合物成膜后的研究结果表明,该膜具有良好的机械性能和电化学性能,可能在质子交换膜燃料电池中得到应用.     

Time-dependent quantum wave packet and quasiclassical trajectory studies of the Au(2S) + H2(X1∑+g) → AuH(X1∑+g) + H(2S) reaction

The time-dependent quantum wave packet (TDWP) and quasiclassical trajectory calculations (QCT) are carried out for the Au(²S) + H₂(X¹∑⁺_g) → AuH(X¹∑⁺_g) + H(²S) reaction on a global potential energy surface. The reaction probabilities at a series of J values, integral cross sections (ICSs) and differential cross sections of the title reaction are calculated by the TDWP method. For reaction probabilities, there are a mass of sharp oscillations at low collision energy, which can be attributed to resonances supported by the potential well. Due to the endothermicity of the title reaction, the total ICS shows a threshold about 1.53 eV. In order to further investigate the reactive mechanism, the lifetime of complex is calculated by QCT method. At the low collision energy, most intermediate complexes are long lived, which implies that the reaction is governed by indirect reactive mechanism. With the collision energy increasing, the direct reactive mechanism occupies the dominant position. Due to the change of the reactive mechanism, the angular distribution shifts toward the forward direction with collision energy increasing. The isotopic variant, Au + D₂→AuD + D reaction, is also calculated by TDWP method. The calculated reaction probabilities and ICSs show that the isotope effect reduces the reactivity.     

An ab initio Study of Intermolecular Potential for Ne-HBr Complex

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｒａｒｅ ｇａｓｈｙｄｒｏｇｅｎｈａｌｉｄｅ (Ｍ—ＨＸ)ｃｏｍｐｌｅｘｅｓｈａｖｅｌｏｎｇｂｅｅｎｓｔｕｄｉｅｄｆｏｒｉｎｓｉｇｈｔｓｉｎｔｏｔｈｅｎａｔｕｒｅｏｆｉｎ ｔｅｒｍｏｌｅｃｕｌａｒｆｏｒｃｅｓａｎｄｄｅｔａｉｌｓｏｆｉｎｔｅｒ ａｎｄｉｎｔｒａｍｏｌｅｃｕｌａｒｄｙｎａｍｉｃｓ .1,2 ＳｙｓｔｅｍａｔｉｃｉｎｖｅｓｔｉｇａｔｉｏｎｓｏｆｔｈｅｃｏｍｐｌｅｘｅｓｏｆＸｅ ,Ｋｒ,Ａｒ,ａｎｄｌａｔｅｌｙＮｅｗｉｔｈＨＦ ,ＨＣｌ,ＨＢｒａｎｄｔｈｅｉｒｄｅｕｔｅｒａ…     

Silicene,a promising new 2D material

Silicene is emerging as a two-dimensional material with very attractive electronic properties for a wide range of applications; it is a particularly promising material for nano-electronics in silicon-based technology. Over the last decade, the existence and stability of silicene has been the subject of much debate. Theoretical studies were the first to predict a puckered honeycomb structure with electronic properties resembling those of graphene. Though these studies were for free-standing silicene, experimental fabrication of silicene has been achieved so far only through epitaxial growth on crystalline surfaces. Indeed, it was only in 2010 that researchers presented the first experimental evidence of the formation of silicene on Ag(1 1 0) and Ag(1 1 1), which has launched silicene in a similar way to graphene. This very active field has naturally led to the recent growth of silicene on Ir(1 1 1), ZrB₂(0 0 0 1) and Au(1 1 0) substrates. However, the electronic properties of epitaxially grown silicene on metal surfaces are influenced by the strong silicene–metal interactions. This has prompted experimental studies of the growth of multi-layer silicene, though the nature of its “silicene” structure remains questionable. Of course, like graphene, synthesizing free-standing silicene represents the ultimate challenge. A first step towards this has been reported recently through chemical exfoliation from calcium disilicide (CaSi₂). In this review, we discuss the experimental and theoretical studies of silicene performed to date. Special attention is given to different experimental studies of the electronic properties of silicene on metal substrates. New avenues for the growth of silicene on other substrates with different chemical characteristics are presented along with foreseeable applications such as nano-devices and novel batteries.     

Pure and mixed gas permeation through a composite polydimethylsiloxane membrane

A thin polydimethylsiloxane (PDMS) layer on polyethersulfone (PES) support was synthesized and pure and mixed gas permeation of C₃H₈, CH₄, and H₂ through it was measured. At first, a macroporous PES support was prepared by using the phase inversion method and characterized. Then, a thin layer of PDMS was coated over the support. Finally, permeation behavior of the synthesized composite membrane was investigated by pure and mixed gas experiments under various operating conditions. The synthesized PDMS/PES membrane showed much better gas permeation performance than others reported in the literature. Pure gas experiments showed that increase in the transmembrane pressure increases the permeability coefficient of heavier gases, C₃H₈, while decreases those of lighter ones, CH₄ and H₂. Exactly opposite behavior was observed in mixed gas experiments due to the competitive sorption and diffusion in the plasticized polymer matrix. Temperature was realized to induce similar effects on the permeability of pure and mixed gases. As expected, in rubbery membranes such as PDMS, permeability values of more condensable gases decrease with increasing temperature, whereas those of permanent gases increase. In the case of mixed gas experiments, increase in the C₃H₈ concentration in feed led to increase in the permeabilities of all the components due to the C₃H₈‐induced swelling of the PDMS film. High C₃H₈/H₂ and C₃H₈/CH₄ ideal selectivities of 22.1 and 14.7, respectively, at a transmembrane pressure of 7 atm as well as reasonable C₃H₈ separation factor (SF) values for all mixed gas experiments (in the range of 8.1–16.8) demonstrated the ability of the synthesized PDMS/PES membrane for the separation of organic vapors from permanent gases. Copyright © 2009 John Wiley & Sons, Ltd.