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25 September 2007, Volume 23 Issue 5

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Content of Chemical Research in Chinese Universities Vol.23 No.5(2007)

2007, 23(5):  0-0.  doi:

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Articles

Trinuclear Metal Complexes Based on 1,10-Phenanthroline Derivates as Catalysts for Cleavage of a RNA-Model Substrate

XU Xin-he , LIN Hai , LIN Hua-kuan

2007, 23(5):  493-499.  doi:

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Two multidentate ligands 2,9-di[6'-(2"-hydroxyl-3"-methoxyphenyl)-n-2',5'-diazahexyl]-1,10-phenanthroline(LA) and 2,9-di(6'-α-phenol-n-2',5'-diazahexyl)-1,10-phenanthroline(LB) were synthesized and fully characterized. Protonation of the ligands and the stability of the complexes of the ligands with divalent metal ions were investigated. The trinuclear metal complexes [Cu(Ⅱ) and Zn(Ⅱ)] of the ligands were studied, as catalysts, for the transphosphorylation of the RNA-model substrate 2-hydroxypropyl-p-nitrophenyl phosphate(HPNP). The second-order rate constants of HPNP-hydrolysis catalyzed by M₃L and M₃LH_-1 were obtained, which indicated that Zn₃LBH_-1 was the most efficient catalyst among them. The proposed mechanisms included the activation of the substrate via binding to the metal ions and intramolecular nucleophilic attack by the deprotonated C2-hydroxyl of HPNP.

Rapid Synthesis of Size-controlled Gold Nanoparticles by Complex Intramolecular Photoreduction

DONG Shou-an, YANG Sheng-chun , TANG Chun

2007, 23(5):  500-504.  doi:

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A rapid synthesis of size-controlled gold nanoparticles was proposed. The method is based on the sensitive intramolecular photoreduction reaction of Fe(Ⅲ)-EDTA complex in chloroacetic acid-sodium acetate buffer solution, where Fe(Ⅱ)-EDTA complex generated by photo-promotion acts as a reductant of AuCl₄^- ions. Gold nanoparticles formed were stabilized by EDTA ligand or other protective agents added. As a result, well-dispersed gold nanoparticles with an average diameter range of 6.7 to 50.9 nm were obtained. According to the characterizations by the UV spectrum and TEM, the intramolecular charge transfer of the excited states of complex Fe(Ⅲ)-EDTA and the mechanism of forming gold nanoparticles were discussed in detail.

Preparation and Characterization of Dichlorocarbene Modified Multiple-walled Carbon Nanotubes

YU Jin-gang, HUANG Ke-long, HONG Yong , HUANG Du-shu

2007, 23(5):  505-507.  doi:

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Multiple-walled carbon nanotubes were functionalized by cycloaddition of dichlorocarbene. The chemical modification was performed by using chloroform and sodium hydroxide. Various phase transfer catalysts were used to increase the efficiency of the reaction. Benzyltriethylammonium chloride used as phase transfer catalyst could highly enhance the effect of functionalization. Elemental analysis was used to evaluate the degree of functionalization. Characterization was performed using scanning electron microscopy(SEM) and transmission electron microscopy(TEM). Fourier transform infrared spectroscopy(FTIR) and energy-dispersive X-ray spectroscopy(EDS) were used to confirm the resulting material.

Facile Synthesis and Catalytic Properties of β-Co(OH)₂ and Mg(OH)₂ Nanoplates

SUN Ling-na , WANG Ke-li , LUO Sheng-jun , GUO Qing-rong , HU Chang-wen

2007, 23(5):  508-510.  doi:

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β-Co(OH)₂ and Mg(OH)₂ nanoplates were synthesized via a facile template-free hydrothermal approach. The different conditions of preparation and catalytic properties of the products were studied and discussed. The products were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, selected area electron diffraction(SAED), and gas chromatograph.

Phenol Solvothermal Synthesis of JBW-Type Zeolites

WEI Bo , WANG Ye , XIN Ming-hong , QIU Shi-lun

2007, 23(5):  511-513.  doi:

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Phenol was used as an aromatic and acidic solvent in solvothermal synthesis. JBW- type zeolites were successfully synthesized in a phenolic system. The as-synthesized microporous crystals were characterized by powder X-ray diffraction analysis and scanning electron microscopy techniques. The results indicate that phenol is a good organic solvent and has a huge potential of application in studying crystallization mechanism and synthesizing novel microporous materials.

Rapid and Sensitive LC-MS/MS Method for Quantification of Fexofenadine in Human Plasma——Application to a Bioequivalence Study in Chinese Volunteers

TENG Guo-sheng , TENG Le-sheng , WU Yi , TANG Yun-biao, , LIU Lan-ying , GU Jing-kai

2007, 23(5):  514-517.  doi:

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A rapid and sensitive liquid chromatography-tandem mass spectrometry method(LC-MS/MS) was developed and validated for the quantification of fexofenadine in human plasma, to conduct comparative bioavailability studies. Human plasma was extracted with a mixture of dichloromethane-diethyl ether(volume ratio 2:3) in a basic environment and the extract was separated on a C18 column with a mobile phase consisting of acetonitrile-methanol-10 mmol/L ammonium acetate(volume ratio 45:45:10). The analytes were detected via electrospray ionization(ESI) tandem mass spectrometry in the multiple-reaction-monitoring(MRM) mode. The linearity was within a range of 1—1000 ng/mL. The intra- and inter-day precision were<4.1% and<4.8%, respectively, and the accuracy was in the range of 95.0%—105%. The method was applied to the quantification of fexofenadine human plasma from 20 healthy male Chinese volunteers, according to a single dose, randomized, two-way crossover design with a two-week washout period. The mean values of major pharmacokinetic parameters of ρ_max, AUC_0—48, AUC_0—∞, t_max, and t_1/2 were determined from the plasma concentration. The analysis of variance(ANOVA) did not show any significant difference between the two products of fexofenadine and 90% confidence intervals fell within the acceptable range for bioequivalence.

Application of Near Infrared Diffuse Reflectance Spectroscopy with Radial Basis Function Neural Network to Determination of Rifampincin Isoniazid and Pyrazinamide Tablets

DU Lin-na , WU Li-hang , LU Jia-hui , GUO Wei-liang , MENG Qing-fan , JIANG Chao-jun , SHEN Si-le , TENG Li-rong

2007, 23(5):  518-523.  doi:

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Partial least squares(PLS), back-propagation neural network(BPNN) and radial basis function neural network(RBFNN) were respectively used for estalishing quantative analysis models with near infrared(NIR) diffuse reflectance spectra for determining the contents of rifampincin(RMP), isoniazid(INH) and pyrazinamide(PZA) in rifampicin isoniazid and pyrazinamide tablets. Savitzky-Golay smoothing, first derivative, second derivative, fast Fourier transform(FFT) and standard normal variate(SNV) transformation methods were applied to pretreating raw NIR diffuse reflectance spectra. The raw and pretreated spectra were divided into several regions, depending on the average spectrum and RSD spectrum. Principal component analysis(PCA) method was used for analyzing the raw and pretreated spectra in different regions in order to reduce the dimensions of input data. The optimum spectral regions and the models' parameters were chosen by comparing the root mean square error of cross-validation(RMSECV) values which were obtained by leave-one-out cross-validation method. The RMSECV values of the RBFNN models for determining the contents of RMP, INH and PZA were 0.00288, 0.00226 and 0.00341, respectively. Using these models for predicting the contents of INH, RMP and PZA in prediction set, the RMSEP values were 0.00266, 0.00227 and 0.00411, respectively. These results are better than those obtained from PLS models and BPNN models. With additional advantages of fast calculation speed and less dependence on the initial conditions, RBFNN is a suitable tool to model complex systems.

Investigation of the Interaction Between Sodium(meta) Arsenite and Catechin via ESI Tandem Mass Spectrometry

CUI Sheng-yun , WEN Jin-feng , KIM Seung-jin , LEE Yong-ill

2007, 23(5):  524-529.  doi:

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Catechin, one of the main components of green tea, is considered to have the remedy effect of arsenic poison, although the chemical mechanism is not well known. In this study, sodium(meta) selenite, which is used as herbicide and insecticide as well as rodenticide, was simply mixed with catechin in the CH₃OH/H₂O(volume ratio 50:50) solution to investigate the interaction between toxic inorganic arsenic compound and catechin via ESI tandem mass spectrometry. The interaction products of mono-methylated arsenic with catechin in the presence of methanol were identified in the negative mode. Collission induced dissociation(CID) mass spectrometric measurements indicate that monomethylated arsenic was “alkylated” strongly by conjugation at the sites of C2' and C5' in the phenyl ring B of the catechin. The interaction mechanism between sodium(meta) arsenite and catechin was proposed. The results provide useful information to understand the chemical pathway of the detoxification of the arsenic toxicity by catechin.

Megastigmane Glycosides from Polygala hongkongensis Hemsl

WU Jian-feng, , CHEN Si-bao,5 , GAO Jing-chun5 , WU Li-jun , CHEN Shi-lin,5 , TU Peng-fei

2007, 23(5):  530-532.  doi:

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Two new megastigmane glycosides, 7Z-roseoside, and 7Z-trifostigmanoside Ⅰ, as well as, four known compounds, trifostigmanoside Ⅱ, epimedin C, 3',7-dihydroxy-4'-methoxyisoflavone-7-D-glucopyranoside, and formenonetin, were isolated from Polygala hongkongensis Hemsl. The structures of the isolated compounds were established on the basis of UV, IR, NMR, and MS spectral data. Megastigmane glycosides(1—3) were isolated from the family Polygalaceae for the first time.

Synthesis, Mass Spectrometric Studies, and Biological Evaluation of 3,5-Dimethoxyhomophthalic Acid and Related Compounds

GHULAM Qadeer , NASIM Hasan-rama , FAN Zhi-jin

2007, 23(5):  533-537.  doi:

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3,5-Dimethoxyhomophthalic acid was synthesized in four steps from 3,5-dimethoxycinnamic acid via a series of reactions including cyclization of 3-(3',5'-dimethoxyphenyl)propionic acid to 5,7-dimethoxy-1-indanone and oxidative decomposition of methyl-2-hydroxy-2-[5,7-dimethyoxy-1-oxo-1H-inden-2(3H)-ylidene]acetate to 3,5-dimethoxyhomophthalic acid. The synthesized compounds were characterized by elemental analysis, IR, ¹H NMR, and MS. The biological evaluation experiments of 3,5-dimthoxyhomophthalic acid and the related synthesized compounds were also carried out. Naturally occurring biologically active isocoumarins were prepared in a single step by the condensation of the homophthalic acid with appropriate acid chlorides.

Synthesis of Poly(N-vinylpyrrolidone) Nanofibers Containing Gold Nanoparticles via Electrospinning Technique

DU Jian-shi , YANG Qing-biao , BAI Jie , WANG Shu-gang , ZHANG Chao-qun , LI Yao-xian

2007, 23(5):  538-540.  doi:

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Poly(N-vinylpyrrolidone)(PVP) nanofibers containing gold nanoparticles were prepared by electrospinning method. This simple route was used to prepare composites on a large scale, and the syntheses are simple. The optical property of gold nanoparticles in PVP aqueous solution was investigated by UV-Visible absorption spectra. The morphology of the fibers and the distribution of particles were characterized by transmission electron microscopy. The structure of the composite was characterized by Fourier transform infrared spectroscopy.

New ent-Isopimarane Diterpene from Mangrove Excoecaria agallocha L.

LI Xiang, , LEI Jun , ZHENG Yi-nan , Sattler Isabel , LIN Wen-han

2007, 23(5):  541-543.  doi:

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A new ent-isopimarane diterpenoid, Agallochaone A(1), together with the known 8,13-epoxy-14-labden-3-one(2) and Excoecarin B(3) were isolated from the whole plant of mangrove Excoecaria agallocha L. and identified on the basis of a detailed spectral analysis, including 2D NMR spectrometry and HRESI-MS.

Synthesis of New Ligand 1,2-Bis{di[(R,R)-1,3,2-oxzaphosphlidine]phosphino}ethane with C₂-symmetric Axis and Application in Rh-catalyzed Asymmetric Hydrogenation

GONG Da-chun , ZHOU Hua , WEI Ping , OUYANG Ping-kai

2007, 23(5):  544-548.  doi:

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New ligand 1,2-bis{di[(R,R)-1,3,2-oxzaphosphlidine]phosphino}ethane [(R,R)-BDOPPEs 1, 2, 3 and 4] with C₂-symmetric axis and bearing nitrogen and oxygen were synthesized from readily available optically active amino alcohols. Rh complexes with these ligands were highly enantioselective catalysts for asymmetric hydrogenation of N-benzoyldehydroamino acid derivatives and α-functionalized ketones in 99%e.e. and 98%e.e., respectively. This new class of (R,R)-BDOPPEs 1, 2, 3 and 4 gave much more effectivity and enantionselectivity than their corresponding non-C₂-asymmetric aminophosphine phosphinite.

Facile Aldol Reaction Between Unmodified Aldehydes and Ketones in Bronsted Acid Ionic Liquids

LIU Bao-you , ZHAO Di-shun , XU Dan-qian , XU Zhen-yuan

2007, 23(5):  549-553.  doi:

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A series of condensation reactions of unmodified ketones and aromatic aldehydes to prepare α,β-unsaturated carbonyl compounds by means of Aldol reactions in Bronsted acid ionic liquids(BAILs) was explored. 1-Butyl-3-methylimidazolium hydrogen sulphate(BMImHSO₄) acting as an effective media and catalyst in aldol reactions was compared with other BAILs, with the advantages of high conversion and selectivity. The product was easily isolated and the left ionic liquid can be readily recovered and reused at least 3 times with almost the same efficiency. The scope and limitation of the present method were explored and the possible catalytic mechanism was speculated.

Dictamine Stimulates Cystic Fibrosis Transmembrane Conductance Regulator Cl^- Transport

LIU Jun , LIU Li-dan , WANG Su-mei , XU Li-na , YU Bo , LIN Sen , HOU Shu-guang , ZHOU Na , JIN Ling-ling , YANG Hong

2007, 23(5):  554-557.  doi:

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Dictamine is a furoquinoline alkaloid isolated from Dictamus dasycarpus Turcz. In the present study, we found that dictamine is able to stimulate the chloride transport activity of wild-type and ΔF508 mutant CFTR. The activity is cAMP-dependent and can be completely reversed by specific CFTR inhibitor CFTRinh-172. In addition, dictamine can further increase the chloride transport activity when CFTR is maximally activated by the combination of cAMP stimulators forskolin(FSK) and IBMX, suggesting direct interaction of dictamine with CFTR. Dictamine may be useful for probing CFTR channel gating mechanisms and used as a lead compound to develop the pharmacological therapy of CFTR-related diseases such as idiopathic chronic pancreatitis and keratoconjunctivitis sicca and cystic fibrosis.

Cellular Adhesion Tripeptide RGD Inhibits Growth of Human Ileocecal Adenocarcinoma Cells HCT-8 and Induces Apoptosis

WANG Hua , ZENG Hong-bin , YANG Shao-juan , GAO Shen , HUANG Yi-bing , HOU Rui-zhen , ZHAO Mi-feng , XU Li , ZHANG Xue-zhong

2007, 23(5):  558-561.  doi:

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The tripeptide, Arg-Gly-Asp(RGD) motif is an integrin-recognition site found in adhesive proteins present in extracellular matrices(ECM) and in the blood. HCT-8 cells were treated with cellular adhesion tripeptide RGD at various concentrations. MTT assay was performed to examine the growth and proliferation of HCT-8 cells after treatment with RGD for 48 h. Haematoxylin and Eosin(HE) staining and electromicroscope were used to observe the morphology of apoptotic cells. Survivin and flow cytometry were also used to analyze the HCT-8 apoptosis. Cellular adhesion tripeptide RGD significantly inhibits the growth and proliferation of HCT-8 cells in a dose-dependent manner and induces apoptosis of HCT-8. These results indicate that cellular adhesion tripeptide RGD inhibits the growth and proli-feration of tumor HCT-8 cell, probably by the aid of inducing apoptosis of HCT-8 cell.

Urea-induced Inactivation and Unfolding of Recombinant Phospholipid Hydroperoxide Glutathione Peroxidase from Oryza sativa

WANG Feng , ZHOU Hui-ping , KONG Bao-hua , FAN Jing-hua , CHEN Hai-ru , LIU Jin-yuan

2007, 23(5):  562-566.  doi:

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Phospholipid hydroperoxide glutathione peroxidase is an antioxidant enzyme that has the highest capability of reducing membrane-bound hydroperoxy lipids as compared to free organic and inorganic hydroperoxides amongst the glutathione peroxidases. In this study, urea-induced effects on the inactivation and unfolding of a recombinant phospholipid hydroperoxide glutathione peroxidase(PHGPx) from Oryza sativa were investigated by means of circular dichroism and fluorescence spectroscopy. With the increase of urea concentration, the residual activity of OsPHGPx decreases correspondingly. When the urea concentration is above 5.0 mol/L, there was no residual activity. In addition, the observed changes in intrinsic tryptophan fluorescence, the binding of the hydrophobic fluorescence probe ANS, and the far UV CD describe a common dependence on the concentration of urea suggesting that the conformational features of the native OsPHGPx are lost in a highly cooperative single transition. The unfolding process comprises of three zones: the native base-line zone between 0 and 2.5 mol/L urea, the transition zone between 2.5 and 5.5 mol/L urea, and the denatured base-line zone above 5.5 mol/L urea. The transition zone has a midpoint at about 4.0 mol/L urea.

Cyclin A-Cdk2 Phosphorylates BH3 only Protein Bad in vitro and in vivo

HE Kan , CHEN Yue , LI Jing-hua, , ZHAN Zhuo , WU Yong-ge , KONG Wei , JIN Ying-hua

2007, 23(5):  567-570.  doi:

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Increasing evidence suggests that Cyclin A-Cdk2 activity is required in the apoptosis process induced by various stimuli. To determine a specific substrate of Cyclin A-Cdk2 for apoptosis, in this study, we carried out an in vitro kinase assay using immunoprecipitated complex Cyclin A-Cdk2 as an enzyme source, and recombinant protein GST-Bad as a substrate. Our study showed that Bad was clearly phosphorylated by Cyclin A-Cdk2 in vitro. To examine whether protein Bad can also be phosphorylated by Cyclin A-Cdk2 kinase in vivo, we transiently overexpressed protein Bad with Cyclin A or Cdk2-dn, a dominant negative version of Cdk2, in Hela cells and determined the phosphorylation status of protein Bad. The test showed that protein Bad was clearly phosphorylated in Cyclin A overexpressed cells, but not in Cdk2-dn or mock transfectent. Moreover, etoposide also caused the phosphorylation of endogenetic Bad. In conclusion, here we provide first time evidence that protein Bad can be a substrate of Cyclin A-Cdk2 apoptosis for in vitro and in vivo.

Enhancement of Two-photon Absorption by Ce³⁺ Sensitization in Organic Dyes

LI Jian-fu , SUN Cheng-lin , ZHOU Hai-ling , XU Li-hua , YANG Qing-xin , JIANG Zhan-kui,

2007, 23(5):  571-573.  doi:

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The two-photon absorption(TPA) and TPA-induced frequency upconversion emission properties of the dyes 4-[P-(dicyanoethylamino) crystal]-N-methypyrdinium iodide and the complex of 4-[P-(dicyanoethylamino) crystal]-N-methypyrdinium iodide and Ce(NO₃)₃ were experimentally studied. It was found that the TPA cross section for the dye sensitized by Ce³⁺ is two factors larger than that of the dye without being sensitized. A three-level system model of the dye molecules was used to analyze the enhancement of TPA by the sensitizer Ce³⁺, which indicated that the sensitizer results in the increase of the transition dipole moment from the one-photon allowed excited state(1Bu) to the two-photon allowed excited state(2Ag).

Low-temperature Heat Capacities and Thermodynamic Properties of Hydrated Sodium Cupric Arsenate [NaCuAsO₄·1.5H₂O(s)]

CHEN Jing-tao , DI You-ying , TAN Zhi-cheng , SUN Li-xian

2007, 23(5):  574-578.  doi:

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Low-temperature heat capacities of the solid compound NaCuAsO₄·1.5H₂O(s) were measured using a precision automated adiabatic calorimeter over a temperature range of T=78 K to T=390 K. A dehydration process occurred in the temperature range of T=368—374 K. The peak temperature of the dehydration was observed to be T_D=(371.828±0.146) K by means of the heat-capacity measurement. The molar enthalpy and entropy of the dehydration were Δ_DH_m=(18.571±0.142) kJ/mol and Δ_DS_m=(49.946±0.415) J/(K·mol), respectively. The experimental values of heat capacities for the solid(Ⅰ) and the solid-liquid mixture(Ⅱ) were respectively fitted to two polynomial equations by the least square method. The smoothed values of the molar heat capacities and the fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were tabulated at an interval of 5 K.

Diffusion of Acetic Acid Across Oil/Water Interface in Emulsification-Internal Gelation Process for Preparation of Alginate Gel Beads

LIU Xiu-dong , YU Wei-ting , LIN Jun-zhang , MA Xiao-jun , YUAN Quan

2007, 23(5):  579-584.  doi:

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Alginate has been widely used in cell microencapsulation and drug delivery systems in the form of gel beads or microcapsules. Although an alternative novel emulsification-internal gelation technology has been established and both the properties and the potential applications of the beads in drug delivery systems have been studied, the mechanism has not been well understood compared with the traditional droplet method(external gelation technology). On the basis of our previous knowledge that the novel technology is composed of complicatedly consecutive processes with multistep diffusion and reaction, and the diffusion of acetic acid across oil/water interface being the prerequisite that determines the occurrence and rate for the reactions and the structures and properties of final produced gel beads, a special emphasis was placed on the diffusion process. With the aid of diffusion modeling and simple experimental design, the diffusion rate constant and diffusion coefficient of acetic acid across oil/water interface were determined to be in the orders of magnitude of 10^-6 and 10^-16, respectively. This knowledge will be of particular importance in understanding and interpreting the formation, structure of the gel beads and the relationship between the structure and properties and guiding the preparation and quality control of the gel beads.

Selective Oxidation of Toluene with Hydrogen Peroxide Catalyzed by V-Mo-based Catalyst

WU Jun-ping, WANG Xue-qin, ZHU Liang-fang, LI Gui-ying , HU Chang-wei

2007, 23(5):  585-591.  doi:

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The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied. The promotion effect of Mo on the catalysts was studied with V/Al₂O₃ and Mo/Al₂O₃ as reference samples. The catalysts were characterized by XRD, TPR, and XPS techniques. The results show that the addition of Mo to V/Al₂O₃ may change the distribution of V species on Al₂O₃ surface. Over V-Mo/Al₂O₃ catalyst, highly dispersed amorphous V species facilitates benzaldehyde formation, and crystalline V₂O₅ species increases the conversion of toluene but decreases the selectivity to benzaldehyde, while AlVMoO₇ species favors both the conversion of toluene and the formation of cresols. The yield of benzaldehyde depends remarkably on the surface O/Al and Mo/V atomic ratios, and gets to a maximum value of 13.2% with a selectivity of 79.5% at an O/Al atomic ratio of 3.0 and Mo/V atomic ratio of 0.7.

Determinations of the Configuration of C-20 in Derivatives of Adynerin Using DFT/HF Methods

HUA Yan,REN Jie, CHEN Chang-xiang,ZHU Hua-jie

2007, 23(5):  592-597.  doi:

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The configurations of C-20 in derivatives of novel 5α-adynerin type, co-existing glycoside in pair, were identified with the calculated chemical shifts of carbon at the B3LYP/6-311+G(2d,p) level. These glycosides are unusual cardic aglycones without the common olefin bond in ring E.

Modulating Bandgap and HOCO/LUCO Energy of Semiconducting Polymer by Copolymerization or Incorporation of Electron Withdrawing/Releasing Groups

YAN Liu-ming , LU Wen-cong

2007, 23(5):  598-601.  doi:

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The modulation of bandgap and HOCO/LUCO energies of conjugated polymers by copolymerization or by incorporation of electron withdrawing/releasing groups is studied. The study was conducted by band structure calculation applying density functional theory with generalized gradient approximation. The polymers and copolymers were modeled as 1D infinite system with periodical boundary condition along the molecular direction. It is concluded that the bandgap and HOCO/LUCO energies of conjugated polymers depend on both electron withdrawing/releasing effects and non-bonding interaction between a side group and the conjugated systems.

Determination of Specific Refractive Index Increment (dn/dc)_μ at a Constant Chemical Potential, for Solutions of Polymer in Mixed Solvents by the GPC Method

WANG Qing-guo , LI Xiao-wen , CHENG Rong-shi

2007, 23(5):  602-606.  doi:

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A new chromatographic method is described for the determination of specific refractive index increment (dn/dc)_μ at a constant chemical potential, for polymer/mixed solvent systems. In this method the (dn/dc) is obtained by measuring the areas of solvated-polymer peaks when the mixed solvent is used as an eluent. Values of (dn/dc)_μ for the poly(dimethylsiloxane)(PDMS)-benzene-methanol system, determined by the proposed method are in good agreement with those determined by the conventional dialysis method. The new approach has the advantages of simplicity, fast speed, and high reproducibility. The experimental results for stearic acid-chloroform-methanol system show that this method can also be applied to nonpolymer/mixed solvent systems for the determination of (dn/dc)_μ.

Influence of Backbone Structure on Properties of Directly Polymerized Phenoxy Resins from Epichlorohydrin and Various Aromatic Dihydric Phenols Monomers

CAI Hong-li, BI Da-wu, SHAO Ke, ZHONG Shuang-ling , NA Hui

2007, 23(5):  607-612.  doi:

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A series of phenoxy resins was directly prepared through the polymerization of each of the various aromatic dihydric phenols and epichlorohydrin. FTIR and ¹H NMR spectra were recorded to characterize the structures of the re-sins. The GPC curves were used to determine the molecular weight distribution. In addition, the thermal properties of the resins were studied with differential scanning calorimetry(DSC) and thermal gravimetric analysis(TGA). The thermal stabilities of the polymers increased with the content of the benzene ring, pendant group increasing or biphenyl groups emerging. The adhesive properties of the polymers were evaluated in terms of the lap shear strength with Fe-Fe adherends. The fracture mechanisms were determined by SEM observation and it was found that there was an important participation of cohesive fracture mechanisms. Also, it has been demonstrated that the extension of these micro-cohesive mechanisms is directly correlated with the adhesive strength. According to these results, the phenoxy resin containing biphenyl groups presented a higher adhesive strength and could improve the adhesive property of the epoxy/phenoxy system to a certain extent.

Pressure Effects on Thermodynamics of Phase Behavior in Polystyrene/Methylcyclohexane Solutions

LI Hong-fei , JIANG Shi-chun , AN Li-jia , YU Dong-hong

2007, 23(5):  613-621.  doi:

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The calculations presented in this paper are based on the Sanchez-Lacombe(SL) lattice fluid theory. The interaction energy parameter, g₁₂*/k, required in this approach was obtained by fitting the cloud points of polystyrene(PS)/methylcyclohexane(MCH) polymer solutions under pressure. The SL lattice fluid theory was used to calculate the spinodals, the binodals, and the Flory-Huggins(FH) interaction parameter of the solutions. The calculated results show that the SL lattice fluid theory can describe the dependences of thermodynamics of PS/MCH solutions on temperature and pressure very well. However, the calculated enthalpy and the excess volume changes indicate that the Clausius-Clapeyron equation cannot be suitable to describe pressure effect on PS/MCH solutions. Further analysis on the thermodynamics of this system under pressure shows that the role of entropy is more important than the excess volume in the present case.

Letter

Hydrothermal Synthesis of Nanorods and Nanowires of Mg/Al Layered Double Hydroxides

ZHAO Yun , JIAO Qing-ze , DING Xue-jia , ZHANG Li-qun , LIU Yuan-yuan

2007, 23(5):  622-624.  doi:

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In this paper, we reported the hydrothermal syntheses of Mg/Al-SO₄^2--LDH nanorods and nanowires.

Research Notes

Investigation of Aconitine-type Alkaloids from Processed Tuber of Aconitum carmiechaeli by HPLC-ESI-MS/MSⁿ

YUE Hao , PI Zi-feng , ZHAO Yu-feng , SONG Feng-rui , LIU Zhi-qiang , LIU Shu-ying

2007, 23(5):  625-627.  doi:

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In this study, a method HPLC-ESI-MS/MSⁿ was developed for identifying the aconitine-type alkaloids from the extracts of A. carmiechaeli.

C₃-Symmetric Molecules with Axial Chirality and Handed Arrangement of Dipole Fields

XU Wei , JIN Lan , ZHOU Hui , LU Yin-xiang , LAN Bi-jian , ZOU Zhen-guang

2007, 23(5):  628-630.  doi:

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In this article, we recognized an indeed two-state system of C₃-symmetric molecule .