甲基丙烯酸N,N-二甲氨基乙酯与丙烯酰β-环糊精共聚水凝胶的合成及其性能研究

用不同的方法合成了两种结构不同的丙烯酰 β 环糊精酯 (β CD 3 A和 β CD 6 A) ,以此为单体与甲基丙烯酸N ,N 二甲氨基乙酯 (DMAEMA)通过氧化还原自由基引发聚合 ,合成出两类含 β 环糊精结构单元的新型水凝胶 .用核磁共振 ,红外光谱及元素分析对两种单体及共聚物的结构和组成进行了表征 .溶胀实验结果表明 ,两类水凝胶均具有较好的pH、温度及离子强度敏感性 ,且因其交联网络结构不同 ,其溶胀性能有所差异     

Determination of Fibre Pore Structure: Influence of Salt,pH and Conventional Wet Strength Resins

It has been shown, in the present investigation, that the two methods used to investigate the pore size distribution of unbleached chemical pulps, i.e. inverse size exclusion chromatography (ISEC) and nuclear magnetic resonance (NMR), give different average pore radius for the pores inside the fibre wall. This is due to the way in which these experiments are performed and the sensitivity of the methods to different types of pores in the cell wall. It was also shown that the two methods gave different results when changing the pH and the ionic strength of the pulp suspension. The pore radius, as detected with ISEC, decreased with both increasing ionic strength and decreasing pH, indicating a loose structure of the exterior of the fibrillar network. However, the pore radius as detected with NMR, was virtually unaffected when increasing the ionic strength, indicating a very rigid structure of the interior of the fibre wall. Decreasing pH though, lead to a decrease in pore radius indicating that upon protonation of the carboxylic groups in the fibre wall, the electrostatic repulsion is diminished and the average pore radius decreases. The NMR technique was also used to study wet strength aid penetration into the fibre wall. It was shown that wet strength aids with a small molecular weight, penetrated the fibre wall, as detected by a decrease in pore radius. It was also shown that addition of different wet strength aids increased the tensile index of the sheet and decreased the fibre strength, measured as zero span-strength of the sheets.     

聚乙烯醇硫酸钾水凝胶电机械化学行为研究

通过将交联聚乙烯醇硫酸酯化的方法制备了一种新型电刺激响应性聚乙烯醇硫酸钾(PVSK)智能水凝胶,并探讨了溶液离子强度和pH对PVSK水凝胶的溶胀吸水率、机械性能以及电机械化学行为的影响.结果表明,制备的PVSK水凝胶的平衡溶胀比随NaCl溶液离子强度的增大而减小,在pH2.39～10.83范围内基本不受溶液pH的影响;经不同离子强度和pH的NaCl溶液充分溶胀的PVSK水凝胶具有良好的机械性能,在非接触的直流电场作用下,该水凝胶向电场负极弯曲,凝胶的弯曲速度和弯曲偏转量随外加电场强度的增加而增大,随NaCl溶液离子强度的增大出现临界最大值,但不随溶液pH(2.08～10.53)的改变而改变;在循环电场作用下,PVSK水凝胶的电机械化学行为具有良好的可逆性.     

Zur kenntnis ‚Kationen-reicher’︁ Tantalate und Niobate Über Na5TaO5 und Na5NbO5

On Tantalates and Niobates ‘rich in Cations’. On Na₅TaO₅ and Na₅NbO₅ Colourless, transparent single crystals of Na₅TaO₅ [annealed mixtures of Na₂O, Li₂O, and Ta₂O₅, Na : Li : Ta = 6.6 : 1.1 : 1, Ni-cylinder, 1000°C, 75 d] as well as Na₅NbO₅ [annealed mixtures of Na₂O, Li₂O, and Nb₂O₅, Na : Li : Nb = 6.6 : 1.1 : 1, Ni-cylinder, 1000°C, 75 d] have been prepared. Single crystal data show that both isotypic oxides represent a deformed variant of the NaCl-type of structure [Na₅TaO₅: 1154 from 1250 I₀ (hkl), four-cycle diffractometer Philips PW 1100, ω2-θ scan, Ag? Kα , R = 4.88%, space group c2/c with a = 629.3(1) pm, b = 1025.4(2) pm, c = 1004.6(2) pm, b? 106.80(2)°, z = 4 and Na₅NbO₅: 998 from 1247 I₀(hkl), four-cycle diffractometer Philips PW 1100, ω-2θ scan, Ag? Kα , R = 8.58% and R_w = 7.67%, space group C2/2 with a = 629.1(1) pm, b = 1024.4(2) pm, c = 1004.2(2) pm, b? = 106.80(2)°, Z = 4]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, the latter derived from Mean Effective Fictive Ionic Radii, MEFIR, as well as Charge Distribution, CHARDI, are calculated.     

Correlation between C and O chemical shifts and torsional strain in spiroacetals

The relationship between the ¹³C and ¹⁷O NMR chemical shifts and the dihedral energies (non-bonding interactions) of 1,4-dioxaspiro[4.4]nonane, 1,4-dioxa- and 6,10-dioxaspiro[4.5]decane, 1,4-dioxa- and 6,11-dioxaspiro[4.6]undecane, 1,5-dioxaspiro[5.5]undecane, 1,5-dioxa and 7,12-dioxaspiro[5.6]dodecane and 1,6-dioxaspiro[6.6]tridecane were analyzed. These data showed correlation of the non-bonding interactions with the chemical shift of the spiranic carbon, as well as a linear relationship between ¹³C and ¹⁷O.     

Hydrolysis of (CH3)3Sn+ in Various Salt Media

The hydrolysis of trimethyltin(IV) has been studied by potentiometry (H⁺ -glass electrode) and calorimetry in various salt media (NaNO₃, NaCl, KCl, Na₂SO₄, and NaNO₃—NaCl mixtures). The effect of ionic strength on the hydrolysis constants is accounted for by a simple Debye–Hückel type equation and by Pitzer equations. The results allow us to obtain H for hydrolysis and the temperature dependence of the Pitzer parameters. The resulting coefficients can be used to examine the speciation of (CH₃)₃Sn⁺ in multicomponent electrolyte solutions, such as natural waters, over a wide range of temperature and ionic strength.     

Synthesis and burst strength of water‐swollen immunoisolatory tubules

A series of amphiphilic hydrogel tubules have been prepared by copolymerizing/crosslinking hydrophilic poly(dimethylacrylamide) segments with hydrophobic di‐, tri‐, and octamethacrylate‐telechelic polyisobutylene crosslinkers, and their elastic modulus and burst strength in the water‐swollen state were investigated. Because the burst characteristics of hydrogels have not yet been quantitatively investigated, equipment was designed and built to generate fundamental insight into the burst properties of thin‐walled (200–250 μm) narrow lumen (2–3 mm i.d.) water‐swollen tubules. The theory developed to describe quantitatively the inflation behavior of thin‐walled rubber tubules was adapted to treat our experimental observations. Changes in the burst strength, elastic modulus, and expansion during the inflation of hydrogel tubules were interpreted in terms of the molecular weight of the hydrophilic segments between crosslinking sites (M_{c,hydrophilic}), which in turn was calculated according to the rubber elasticity theory. According to these investigations, the burst strength of our water‐swollen amphiphilic tubules is in the 0.2–0.5 MPa range, which is sufficient for implantation and immunoisolatory applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2075–2084, 2002     

Comparison of gas chromatographic and gas chromatographic/mass spectrometric techniques for the analysis of TNT and related nitroaromatic compounds

The use of capillary column gas chromatography and gas chromatography/mass spectrometry for the analysis of a series of standard solutions (0.1 to 10 μg/ml) of 2,4,6-trinitrotoluene (TNT) and eight other nitroaromatic components was evaluated. The techniques included gas chromatography with electron capture detection (GC/ECD), full scan and selected ion monitoring gas chromatography/mass spectrometry with electron impact ionization (EI/FS and EI/SIM), full scan and selected ion monitoring gas chromatography/mass spectrometry with positive ion chemical ionization using methane reagent gas (PICI/FS and PICI/SIM), and full scan and selected ion monitoring gas chromatography/mass spectrometry with negative ion chemical ionization using methane reagent gas (NICI/FS and NICI/SIM). The performance of the techniques was comapared by determining the linear response range, precision, and detection limits of the analyses.     

Aging effect on the mechanical properties of hybrid gels

Sol-gel derived unsupported films and thin rods have been obtained from co-hydrolysis of triethoxysilane and methyldiethoxysilane. The materials are flexible, dense and transparent. Films and rods have been aged for different periods of time in air at room temperature. The elastic modulus has been measured by means of tensile or flexural tests. Measurements showed an increase of elastic modulus with aging time and showed different values for films and rods. The observed evolution of mechanical properties has been related to a corresponding structural modification as highlighted mainly by MAS-NMR studies. Analyses pointed out the crucial role of condensation processes and showed that the stiffness increase arises from the formation of relatively few bonds which link and constrain pre-existing mobile network regions.     

硅酸及其盐的研究 XX聚硅酸溶液中的酸强度与分子结构的关系

本文利用无机酸系列的酸强度(pKa值)与羟基上氧原子的亲电子超离域度S(E)成线性关系的规律性,找出聚硅酸系列的相应线性方程为:并由此推测低聚硅酸溶液中可能存在的硅酸结构:在三聚硅酸溶液中主要存在着六元平面环的三聚体;在四聚硅酸中则主要存在着三种环状的四聚体。