离子液体两相不对称氢甲酰化催化反应的研究

从(R)-BINAP出发制备水溶性磺酸钠盐配体(R)-BINAPS,采用离子液体BF4和PF6为介质,实现其Rh配合物对乙酸乙烯酯的两相不对称氢甲酰化反应.实验结果表明,在以BF4为介质的乙酸乙烯酯不对称氢甲酰化反应中,该催化剂在温和条件下显示出高于相应均相体系的产物ee值和异构醛选择性,并在6次循环使用中,反应产物的ee值、选择性和转化率均无明显改变;在离子液体体系中添加适当的甲苯时,油溶性配体(R)-BINAP与Rh组成的配合物催化剂亦可形成类似的两相反应体系,但其活性和选择性在重复使用中呈明显下降趋势.本文还考察了溶剂体系、膦铑比、温度、压力、时间等的影响,并尝试苯乙烯的两相不对称氢甲酰化反应.     

Viscoelasticity,mechanical properties,and in vivo biocompatibility of injectable polyvinyl alcohol/bioactive glass composite hydrogels as potential bone tissue scaffolds

Abstract

An injectable composite hydrogel composed of polyvinyl alcohol (PVA) and bioactive glass (BG) particles were synthesized by a physical crosslinking approach. The morphology, mechanical properties, and viscoelasticity of the PVA/BG composite hydrogel were characterized. Scanning electronic microscopy (SEM) showed uniform and homogeneous distribution of BG particles throughout the composite hydrogel. The incorporation of 2.5?wt% of BG particles in the composite hydrogel formulations, enhanced the static compressive strength and static elastic modulus by 325% and 150%, respectively. The storage molds (G′) was greater than the loss modules (G′′) at all the frequency range studied, which revealed a self-standing elastic composite hydrogel with a smooth injectability. The PVA/BG composite hydrogel was also implanted subcutaneously in the dorsal region of adult male rats. After 4?weeks of implantation, no inflammatory cells were seen within and around the implant, which indicated that the composite hydrogel was biocompatible. The properties of the synthesized injectable PVA/BG composite hydrogel demonstrate its capability toward bone regeneration.     

Solvation and Ion-Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations

Choline-based electrolytes have been proposed as environmentally friendly and low-cost alternatives for secondary zinc air batteries. Choline acetate [Ch]⁺[OAc]⁻ in protic (D₂O) and aprotic (DMSO-d₆) solvents has been studied by means of concentration-dependent ¹H NMR, viscosity, and density measurements. The viscosities have been calculated on the basis of the Jones-Dole equation and showed that the dominant contribution originates from short-range ion-solvent interactions. Site-specific association affinities were assigned from NMR chemical shift titrations. In DMSO-d₆, the hydroxyl group of choline was found to have the smallest dissociation constant followed by the methyl group of acetate. The corresponding Gibbs energies at low concentration were found to be in agreement with a solvent-separated ion pair (2SIP) configuration, whereas at concentrations above 300 mM, a solvent-shared ion pair (SIP) configuration was assigned. For [Ch]⁺[OAc]⁻ in D₂O, association effects were found to be weaker, attributed to the high dielectric constant of the solvent. On time scales on the order of 100 ms, NMR linewidth perturbations indicated a change in the local rotational dynamics of the ions, attributed to short-range cation-solvent interactions and not to solvent viscosity. At 184 mM, 40 % of the cations in DMSO-d₆ and 10 % in D₂O were found to exhibit short-range interactions, as indicated by the linewidth perturbations. It was found that at about 300 mM, the ions in DMSO-d₆ exhibit a transition from free to collective translational dynamics on time scales on the order of 400 ms. In DMSO-d₆, both ions were found to be almost equally solvated, whereas in D₂O solvation of acetate was stronger, as indicated by the obtained effective hydrodynamic radii. For [Ch]⁺[OAc]⁻ in DMSO-d₆, the results suggest a solvent-shared ion association with weak H-bonding interactions for concentrations between 0.3–1 M. Overall, the extent of ion association in solvents such as DMSO is not expected to significantly limit charge transport and hinder the performance of choline-based electrolytes.     

Speed of Sound, Isentropic Compressibilities, and Excess Molar Volumes of Binary Mixtures Containing p-Dioxane

The speed of sound u in and densities of eight binary mixtures of p-dioxane (p-C₄H₈O₂) with methylcyclohexane (c-C₆H₁₁CH₃), 1-chlorohexane (C₆H₁₃C1), 1-bromohexane (C₆H₁₃Br), p-xylene [C₆H₄(CH₃)₂], propylbenzene (C₆H₅C₃H₇), methyl acetate CH₃COOCH₃), butyl acetate (CH₃COOC₄H₉), and amyl acetate (CH₃COOC₅H₁₁) were measured over the whole composition range at 30°C. Isentropic compressibilities (K _S), Rao's molar sound functions (R), excess molar volumes (V ^E), excess isentropic compressibilities (K _S ^E ) together with relative change in volume V/₁₂ values, have been obtained for all measured mole fractions. The excess partial molar volume (V₁-V ₁ ⁰ ) of p-dioxane in different solvents have also been estimated. The experimental results have been analyzed in terms of the Prigogine–Flory–Patterson theory of solutions.     

Picolinamide-Cu(Ac)2-imprinted polymer with high potential for recognition of picolinamide-copper acetate complex

In this report, with semi-empirical quantum method, we have studied the conformation and energy of supermolecule composed of picolinamide and its positional isomers with methacrylic acid. We tried to explore the reason why picolinamide was not likely to show imprinting effect when using methacrylic acid as functional monomer in our previous work. In order to produce imprinting effect, which was not achieved based on hydrogen bonding interaction, we have synthesized a molecular-imprinted polymer (MIP) based on copper ion coordination in prepolymerization. The complex in prepolymerization was composed of copper(II), acetate, picolinamide and 4-vinylpyridine (4-Vpy). Suprisingly, the MIP had high selectivity to picolinamide-copper acetate complex, and changes of either copper ion, picolinamide or acetate would result in decrease in the imprinting effect. This is also the first example where the high selective recognition of the MIP to its template was achieved mainly by inhibiting the binding of non-template rather than enhancing the binding of the template. And this report can be also looked upon as a first step towards the solution to the problem of imprinting of template that contains intramolecular hydrogen bond.     

Cure kinetics of epoxy resin and thermoplastic polymer

The cure kinetics and morphology of diglycidyl ether of bisphenol A (DGEBA) modified with polyvinyl acetate (PVAc) using diaminodiphenylmethane (DDM) as hardener were investigated through differential scanning calorimetry (DSC) and environmental scanning electron microscopy (ESEM). Isothermal curing measurements were carried out at 150, 120 and 80°C. The kinetic parameters were obtained using the general autocatalytic chemically controlled model. The comparison of the kinetic data indicates that the presence of PVAc does not change the autocatalytic nature of the cure reaction. Two T _g’s were observed in the fully cured samples of the modified systems. ESEM micrographies confirm the biphasic morphology.     

Conductance studies in amide-water mixtures. II. Sodium salts inN,N-dimethylformamide-water mixtures at 35°C

Conductance data for sodium nitrite, chloride, and acetate in water andN,N-dimethylformamide (DMF)-water mixtures (74.82D42.48) for the concentration range 0.001–0.04N, as well as the densities, viscosities, and dielectric constants of the solvent mixtures at 35°C, are reported. The data have been analyzed by the Fuoss (1975) equation. The existence of a maximum in the viscosity at a 13 mole ratio of DMF and water is indicated. The Walden products for all the three salts pass through a maximum while the equivalent conductances show a minimum with increasing DMF content. The maxima in the Walden product are attributed to the dehydration of ions by the cosolvent (DMF).Part I:Indian J. Chem. 14A, 1015 (1976).Deceased.     

铸膜溶剂对CAB膜形态和性能的影响

以ＣＡＢ高分子为膜材料，研究了铸膜液的溶剂体生添加剂对膜形态及选择性渗透Ｎ２、Ｏ２、ＣＨ４、ＣＯ２等气体的影响。溶剂体系以丙酮为基本组分，混合甲酰胺或乙酸，可得到具有好的气体渗透性或气体选择性的非对称膜，通过溶剂的红外光谱羰基吸收峰的偏移，认为溶剂体系有可能存在Ｌｅｗｉｓ酸；碱络合物。     

高含水聚乙烯醇弹性体

本文介绍了用反复冻结～融溶过程制备高含水聚乙烯醇弹性体的方法,并测定了该弹性体的机械、溶解和溶胀性能。结果表明,该弹性体可同时具有很高的含水率(85—90％)和较高的抗张强度(10~5—10~6Pa),且在37℃的水中有良好的稳定性能。     

Hemocompatibility of poly(acrylonitrile-co-N-vinyl-2-pyrrolidone)s: swelling behavior and water states

Hemocompatibility is an essential aspect of blood contacting polymers. Knowledge of the relationship between polymer structure and hemocompatibility is important in designing such polymers. In this work, the effect of swelling behavior and states of water on the hemocompatibility of poly(acrylonitrile-co-N-vinyl-2-pyrrolidone) (PANCNVP) films was studied. Platelet adhesion and plasma recalcification time tests were used to evaluate the hemocompatibility of the films. Considering the importance of surface properties on the hemocompatibility of polymers, static water contact angles were measured by both sessile drop and captive bubble methods. It was found that, on the film surface of PANCNVP with a higher NVP content, adhered platelets were remarkably suppressed and the recalcification time was longer. The total water content adsorbed on the PANCNVP film was determined through swelling experiments performed at temperatures of interest. Differential scanning calorimetry and thermogravimetric analysis were used to probe the states of water in the films. Based on the results from these experiments, it was hypothesized that the better hemocompatibility of PANCNVP films with higher NVP contents was due to their higher free water content, because water molecule exchange at the polymer/liquid interface, facilitated by a high free water content, is unfavorable for the formation of surface bound water, which causes poor hemocompatibility. [diagram in text].