聚砜-尼龙6嵌段共聚物结构的研究

<正> 以金属钠作催化剂合成的聚砜-尼龙6嵌段共聚物对尼龙6的吸水性有一定的改善,而且可以作为聚砜与尼龙共混物的相容剂,但共聚物中聚砜组分的含量都不超过25％。这可能与共聚物的结构有关。近年来的工作表明:反相气相色谱法(IGC)是高聚物结构分析的有用的工具之一。我们试图用反相气相色谱法,通过观察嵌段共聚物     

在位分散聚合聚甲基丙烯酸甲酯/二氧化硅纳米复合材料研究

应用在位分散聚合方法制备了分散相粒径介于１３０ｎｍ左右的聚甲基丙烯酸甲酯／二氧化硅ＰＭＭＡ／ＳｉＯ２纳米复合材料，并利用ＳＥＭ，ＤＭＡ，ＴＧＡ等手段研究了该体系的性能．结果表明，经表面处理的ＳｉＯ２无机填料在复合材料基体中分散均匀，界面粘结好．ＳｉＯ２填充粒子的用量对基体的热稳定性，动态力学行为，光学行为以及拉伸强度，弹性模量，断裂伸长率等力学性能都有较大影响     

A simulation of thermal characteristic parameters with an inverse “S” type curve

A synthetical equation is proposed to characterize the essential features of the inverse “S” type curve on the basis of summing-up simulation approach of “S” type curve. The two physical variables in the model obtained are discussed and the detailed method used to determine the parameters is given. The model is then presented to describe the crystallization of poly(caryleher ether ketone) (PEEK) and thermal decomposition of poly(amide-imide) (PAI) respectively. It is found that some thermal characteristic parameters can be well estimated from the model simu-lated in computer.     

Pore Structure Analysis of Porous Particles by Equivalent Model

Starting from Wheeler's composite theory, which takes both the multilayer adsorption and the capillary condensation into consideration, and assuming the equivalent cylindrical model, we have deduced a strict and relatively simpler formula for the calculation of pore size distribution by solving the integral equation directly. The formula is more convenient for application because of its recursion form. Following the same line of reasoning and using the mean value theorem of definite integrals under different conditions, we have unified the equations of Barrett-Joyner-Halenda, Dubinin, Cranston-Inkley, Dollimore-Heal and Roberts. A table of parameters which is required in the calculation is given. Besides the adsorption of nitrogen, the adsorption with water vapor as the adsorbate is investigated and the corresponding empirical equation of adsorption thickness is given.     

Odd/even effect in the chain length on the enthalpy of micellization of gemini surfactants in aqueous solution

The micellization properties of cationic symmetric gemini surfactants, [CmH(2m+1)(CH3)2N(CH2)6N(CH3)2CmH(2m+1)]Br2 (designated as CmC6CmBr2, with m = 7, 8, 9, 10, 11, 12, and 16), has been investigated by isothermal titration microcalorimetry. The critical micelle concentration (CMC) and enthalpy of micellization (DeltaHmic) were determined from calorimetric titration curves. The linear decreasing of log CMC with increasing the length of the hydrophobic chain is consistent with an increase in the hydrophobicity of the alkyl chain. Interestingly, with increasing the length of the alkyl chain, the DeltaHmic values of the surfactants with even numbered alkyl chains vary from endothermic to exothermic, whereas the DeltaHmic values of the surfactants with odd numbered alkyl chains are all endothermic and tend to become more endothermic. The pronounced even/odd effect in DeltaHmic is discussed with respect to the "donor-acceptor" interaction.     

Enthalpy of Adsorption and Isotherms for Adsorption of Naphthenic Acid onto Clays

The enthalpies of adsorption and the isotherms for adsorption of naphthenic acid onto Na-montmorillonite, Na-kaolinite, and Na-illite were studied by means of calorimetry and the static method at 298.15 K. The results show that the enthalpies of adsorption and saturated adsorption amounts of naphthenic acid on different clays change in the order Na-montmorillonite > Na-illite > Na-kaolinite. The interaction between naphthenic acid and clays is discussed.     

Styrylpyridine-based epoxy resins: Synthesis and characterization

Polymers containing rigid aromatic structures in the chain backbone usually gave high thermal stability and good flammability resistance. Three glycidyl ethers of epoxy resins were prepared from 2,4-di(p-hydroxystyryl)pyridine (2,4-DGESP), 2,6-di-(p-hydroxystyryl)pyridine (2,6-DGESP), and 2,4,6-tri-(p-hydroxystyryl)pryidine (2,4,6-TGESP) to study the relationships of structure to polymer degradation. To prepare a highly crosslinked material, trimethoxyboroxine (TMB) was used as the curing agent. The relative char yields of the three different resins, as measured by TGA, were 2,4-DGESP ≈ 2,6-DGESP > 2,4,6-TGESP. The char yield of the cured 2,6-DGESP varied with different amounts of the TMB curing agent, and was higher than the uncured 2,6-DGESP. The oxygen index increased as a function of thermal curing time for the 2,6-DGESP epoxy resin. An intermolecular Diels–Alder reaction with 2,6-DGESP is proposed as a primary reaction during thermal curing.     

Structural dependence of non-linear optical properties of 4-Dimethylamino-3-cyanobiphenyl

 4-Dimethylamino-3-cyanobiphenyl (4-DMA-3-CB) was characterized with respect to linear and nonlinear optical properties in a crystal as well as in solution. The crystal structure was studied dependent on the crystallization conditions. It is shown that the crystal structure exhibiting NLO-activity can completely be solved by a combination of electron diffraction and computer modeling. There are four molecules per unit cell in the space group Pna2₁ with dimensions a=10.28 Å, b=22.64 Å, c=5.27 Å. From this model structure the values and orientation of the dipole μ and static second order polarizability β can be calculated. Their relevance to the values obtained by a combination of polarization dependent measurements of Electric Field Induced Second Harmonic Generation (EFISH) and Hyper-Rayleigh-Scattering (HRS) in solution are discussed. The molecular second order polarizability tensor was found to be dominated by one single component. The orientations of the dipole and the vectorial parts of the second order polarizability delivered by the semiempirical calculations are in good agreement with the results of the EFISH and HRS-measurements and allow a deeper insight into the nonlinear optical properties of the crystal. Received: 15 April 1996 Accepted: 21 June 1996     

（Z）—3—丁烯基—4,5—二羟基苯酞的合成

（Ｚ）－３－丁烯基苯酞和它的衍生物广泛地存在于微形科植物，如当归、川芎等，这些植物有些是重要的中药材。（Ｚ）－３－丁烯基－４，５－二羟基苯酞是（Ｚ）－３－丁烯基苯酞的类似物；它对前列腺素Ｆ２α具有抑制作用。本文以３，４－二甲氧基苯甲醇（２）或价廉易得的胡椒醇（６）为起始原料，分别经四步反应顺利地合成了（Ｚ）－３－丁烯基－４，５羟基苯酞（１）。和一步是本方法的关键，即利用杂原子诱导的区域选择性的芳环     

Accurate local spin-polarized exchange potential: Reconciliation of generalized Slater and Kohn–Sham methods

Using simple physical arguments, a local spin-polarized exchange potential, V_xσ, is constructed from the single-particle Hartree–Fock (HF ) potentials (generalized Slater method) that reduces to the usual Kohn–Sham (KS ) result in the uniform gas limit. Numerical results for 10 closed subshell atoms demonstrate that the total energy calculated employing this V_xσ is closer to the exact KS results than those of other standard exchange approximations with electron densities and highest occupied orbital eigenvalues that closely approximate the HF results.