INTERACTION OF POLYVINYLPYRROLIDONE WITH METAL CHLORIDE AQUEOUS SOLUTIONS

Interactions of polyvinylpyrrolidone (PVP) with metal chlorides (MgCl2, CaCl2, KC1 and BaC12) have been investigated by viscometric and spectrophotometric techniques in aqueous solutions. Intrinsic viscosity [η] of (PVP) has shown a discontinuity with varying concentration of metal chlorides. The decreasing order of effectiveness of cation is K1 ＞Ca2 ＞ Mg2 ＞ Ba2 for poly(vinylpyrrolidone) solution. Changes in the absorption spectra of the cosolutes were observed in the presence of PVP in the lower limit of the UV-visible region i.e. 200-210 nm. These changes were attributed to interaction of PVP molecules with the cosolute molecules. As the concentration of the cosolute increased, a red shift in the peaks was observed, indicating an increase in interaction between PVP and cosolutes.     

POLYMER SUPPORT EFFECTS OF METAL COMPLEXES FOR CATALYSIS*

In the course of investigating the catalytic behavior of metal complexes forring opening metathesis polymerization of cycloolefins, metathesis, hydroformylation andselective hydrogenation of olefins experimental results time and again indicate the pres-ence of effects of macromolecular supports -the utilization of macromolecular supportsincreases obviously the activity, selectivity, and stability of the catalysts and so as to in-crease the conversion of substrates, yields of reactions, properties of formed polymers andso on. Discussed these effects on the basis of the authors' experiments.     

MIXED EXCITATION IN ELECTROLUMINESENCE*

Anong the present three types of electric field-induced luminescence we noticed similarities between the inorganicand organic materials in electric field intensity. In this high electric field range SiO_2 has three functons: acceleration,excitation and multiplication of electrons. Based on the acceleration effect, cathodoluminescence-like emission of organicmolecules and polymers was found. By using the three functions of SiO_2 or II-VI compounds and the heterojunction ofinorganic and organic material we realized different variants of mixed excitation in electroluminescence.     

POLYMERIZATION OF OCTAMETHYLCYCLOTETRASILOXANE WITH HEXAMETHYLDISILAZYL-LITHIUM AS INITIATOR*

 This work focused on the anionic polymerization of octamethylcyclotetrasiloxane (D₄, D = Me₂SiO_2/2) initiated by a new kind of initiator hexamethyldisilazyl-lithium (MM^NLi). ²⁹Si-NMR spectroscopy and gas chromatography (GC) were used to characterize the polymerization products. The process was accelerated by adding a small amount of high activity monomer D₃ and by raising the polymerization temperature. At the end of polymerization more than 95% of the monomer was converted to polymer and only a very small amount ofD₄ and D₅ remained in the polymers.     

EFFECT OF WATER ON THE CONDUCTIVITY OF PPQ (ClO_4~-) COMPLEX

The preparation of conducting PPQ film was first reported in the previous paper. It is very interesting that this film is highly sensitive to moisture in air. The hydration and dehydration of the film are accompanied by change not only in color but also in conductivity and UV-visible spectrum. The conducting PPQ is reduced to PPQ and loses its conductivity after being soaked in water.     

STUDY ON THERMAL DECOMPOSITION KINETICS OF URUSHIOL METAL CHELATE POLYMERS

The thermal decomposition kinetics of urushiol-Cu, urushiol-Nd and urushiol-Ti chelatepolymers has been studied by non-isothermal thermogravimetry. The results suggest that thethermal decomposition kinetics of three chelate polymers are all of first order. Their averageactivation energy values of the thermal decomposition calculated by Ozawa-(I) method are 110,79, 136. 98 and 163. 64 kJ mol~(-1) respectively, which increase linearly with the metal valence of themetal chelate polymers     

金属离子的超临界流体萃取技术的进展

超临界流体萃取技术在分离方面发展迅速,应用前景十分广泛。文中综述了超临界流体技术的萃取机理及对金属离子萃取的研究。     

EFFECT OF PAN-MILLING ON RHEOLOGICAL PROPERTIES OF HIGH DENSITY POLYETHYLENE*

The effect of pan-milling on the rheological properties of high density polyethylene (HDPE) was studied. Aninnovative milling apparatus, viz. an inlaid pan-mill, was used. Melt indexer, capillary rheometer, Haake Rheocord 90 single-screw extruder and Brabender rheometer were used to evaluate the rheologieal properties of HDPE. HDPE with higher initialmolecular weight and larger particle size was easier to degrade under pan-milling stress, as indicated by the melt index.Pressure oscillation in capillary flow occurred at significantly higher shear stress and shear rate for milled HDPE than forunmilled HDPE. The apparent shear viscosity of HDPE decreased with increasing times of milling. After milling, the flowactivation energy decreased and thus the sensitivity of viscosity to temperature was reduced. Die pressure and torque duringsingle screw extrusion were reduced significantly after milling. Plasticizing time as measured in a Brabander mixer decreasedmarkedly with increasing milling times.     

DILUTE SOLUTION BEHAVIOR OF CHITOSAN IN DIFFERENT ACID SOLVENTS

Dilute solution behavior of chitosan was studied in formic acid, acetic acid, lactic acid andhydrochloric acid aqueous solution under different pH values. The reduced viscosities, η_(sp)/C,ofchitosan solutions were dependent on the properties of acid and pH value of solvents. For a givenchitosan concentration, η~(sp)/C decreased with the increase of acid concentration, or decreasing pHof solvent, indicating shielding effect of excessive acid similar to adding salt into solution. Thestabilities of dilute chitosan solution in formic acid and lactic acid were better than that in acetic acid and hvdrochloric acid.     

ELECTROCHEMICAL COPOLYMERIZATION OF ANILINE AND AZURE B*

The electrochemical copolymerization of aniline and N,N,N'-trimethylthionin (azure B) in aqueous solutions hasbeen carried out using the potential sweep method, The optimum conditions for the coelectrodeposition are that the pH valueand the temperature of the electrolytic solution are controlled at 5.57 and 30℃, respectively, and the scan potential range isset between - 0.25 and 1.10 V (versus SCE). The copolymerization rate of aniline and azure B is about 3 times larger thanthat of aniline in the absence of azure B. The copolymerization of aniline and azure B was verified from the results of visiblespectra during electrolysis, FTIR spectra and the atomic force microscopy (AFM) images of the polymers. The in situ visiblespectrum for the electrolysis of the solution containing aniline and azure B is different from that of the respective aniline andazure B. The FTIR spectrum of the copolymer is not a superposition of that of polyaniline and poly(azure B). The AFMimage of the copolymer is different from those of polyaniline and poly(azure B) and is not a mixture of individual polymers.The conductivity of thc copolymer synthesized at pH 5.57 is four orders of magnitude higher than that of polyanilinesynthesized under the same conditions, bat in the absence of azure B. The clectrochemical properties of the copolymer aremainly attributed to polyaniline, but the copolymer has a better electrochemical reversibility and a much faster charge transferthan those of polyaniline.     

CONFIGURATION-DEPENDENT PROPERTIES OF POLY(DIMETHYLSILOXANE) CHAIN*

The intermolecular rotational potential energies for poly(dimethylsiloxane) (PDMS) chains aredirectly obtained from a priori probability P_(αβ). Here the differing statistical weight matrices for the Si-Oand O-Si bonds are considered in calculating the configuration partition function. In the Bahar's model, asthe same statistical weight matrices for the Si -O and O- Si bonds are adopted, there exists a large deviationof αpriori probability P_(αβ) between the theory and the molecular dynamics (MD) simulation. Our model givessatisfactory agreement with experiment on the mean-square unperturbed end-to-end distance, the mean-square dipole moment and its temperature dependence, and the molar cyclization equilibrium constants fordimethylsiloxane oligomers. This new rotational isomeric state approach can be widely applied to otherchains, such as -CH_2-C[(CH_2)_mH]_2- and -O-Si[(CH_2)_mH]_2 for arbitrary m.     

THE THEORETICAL STUDY OF ADSORPTION OF METAL IONS ON CHITOSAN

The interactions between metal ions such as Zn2+, Pb2+, Mn2+, Hg2+, Cd2+, Ni2+ and chitosan have been investigated using the model cluster model method and density functional method. Full optimization and frequency analysis of all cluster models have been performed employing B3LYP hybrid method at 3-21G basis set level except metal ions which were invoked to use effective core potential (ECP) method. The energy changes, and the main structural parameters have been obtained during the theoretical study of the adsorption of metal ions on the chitosan. The calculations showed that the coordination modes of metal ions with chitosan models were different, the geometries of Mn2+, Zn2+, Cd2+, Hg2+, Pb2+ ions coordinated with two nitrogen atoms and two oxygen atoms were distorted tetrahedral, while the square planar structure of Ni2+ coordinated two nitrogen atoms and two oxygen atoms was observed. The heat of reaction between six metal ions and chitosan models showed the order: Mn2+ ＞Ni2+ ＞Zn2+ ＞Pb2+ ＞Hg2+ ＞Cd2+, this suggested that the coordination strength of Mn2+ ＞Ni2+ ＞Zn2+ ＞Pb2+ ＞Hg2+ ＞Cd2+.     

BARRIER PROPERTY AND STRUCTURE OF ACRYLONITRILE/ACRYLIC COPOLYMERS

A series of acrylonitrile (AN) copolymers with methyl acrylate (MA) or ethyl acrylate(EA) as comonomer (5--23 wt%) was prepared by free-radical copolymerization. The per-meability coefficients of the copolymers to oxygen and carbon dioxide were measured at1.0 MPa and at 30℃, and those to water vapor also measured at 100% relative humidityand at 30℃. All the AN/acrylic copolymers are semicrystalline. As the acrylate contentincrease, the permeability coefficients of the copolymers to oxygen and carbon dioxide areincreased progressively but those to water vapor are decreased progressively The gas per-meability coefficients of the polymers were correlated with free-volume fractions or the ratioof free volume to cohesive energy.     

THE THEORETICAL STUDY OF ADSORPTION OF METAL IONS ON CHITOSAN

1. INTRODUCTION Chitin, the most abundant natural amino polysaccharide and estimated to be produced annually almost as much as cellulose, is well known to consist of 2-acetamido-2-deoxy-β-D- glucose through α, β(1→4) linkage. Chitin is the major source of surface pollution in coastalareas. Chitosan is the N-deacetylated derivative of chitin and their structures are shown in Fig. 1. Fig. 1 Structures of Chitin and Chitosan Because of the excellent properties such as biocompatibility…     

A SIMPLE METHOD FOR THE INCORPORATION OF LOW MOLECULAR WEIGHT DYES IN ULTRATHIN FILMS

A simple method for the fabrication of ultrathin films containing low molecular weight dye material is introduced(post-adsorption technique). The chromophore used is 4-nitro-4'-decyloxy azobenzene quaternary ammonium salt (azo-10Q).In classical layer-by-layer (LBL) procedures, where the substrate is dipped alternately into the chromophore solution and thecomplementary polyelectrolyte, the chromophore tends to desorb from the film during subsequent immersion in thepolyanion solution, and there is little or no indication of multilayer growth. The extent of desorption depends somewhat onthe selection of polyelectrolyte, the ionic strength and the pH of solution. An alternative approach is to first prepareconventional LBL films from a pair of oppositely charged polyelectrolytes, and then to soak this film into the chromophoresolution, where adsorption by penetration into the LBL film may take place. In preliminary results, a linear dependence ofUV absorbance on layer number of LBL film thus prepared was found, demonstrating the apparent effectiveness of the post-adsorption technique for the preparation of azo-10Q-containing ultrathin films.     

PREPARATION AND FLUORESCENT PROPERTIES OF Eu~(3+)-CONTAINING CORE-SHELL NANOPARTICLES

By using a two-stage soapless emulsion polymerization, four kinds of core-shell nanoparticles have been prepared,which are composed of a polystyrene core having an average diameter of 256 nm and a poly(methyl methacrylate-co-acrylicacid) shell. The transmission electron microscopy (TEM) micrographs and the atomic force microscopy (AFM) imagesevidenced the presence of a core-shell structure. In the infrared spectra, the shift of v_(COOH) to lower wavenumber withincreasing Eu~(3 ) ion content indicates that coordination between the oxygen of the carboxylic group and Eu~(3 ) has occurred.The fluorescence intensity of ~5D_0-~7F_2 transition was observed to reach its maximum with a carboxyl group molar percentageof 40% in the shell and an Eu~(3 )/--COO~- molar ratio of 1:3. The fluorescence intensity ratio of ~5D_0-~7F_2 to ~5D_0-~7F_1 transition reached its maximum with an Eu~(3 )/--COO~- molar ratio of 1:3 for all the four series.     

一些金属氧化物在TiO_2(锐钛矿)载体上的分散 嵌入模型的应用

一些金属氧化物在ＴｉＯ２（锐钛矿）载体上的分散＊嵌入模型的应用徐斌董林陈懿（南京大学化学系亚微观固态化学研究所，南京２１００９３）关键词嵌入模型，金属氧化物，分散容量，锐钛矿我们曾以γ－Ａｌ２Ｏ３，ＣｅＯ２和ＳｉＯ２为载体研究了离子化合物的分散，认为...     

A STUDY ON MECHANICAL PROPERTIES OF γ-RAY IRRADIATED HDPE FILLED WITH SERICITE-TRIDYMITE-CRISTOBALITE*

The effect of γ-ray irradiation on the mechanical properties of high densitypolyethylene(HDPE) filled with sericite-tridymite-cristobalite(STC) was studied. The ex-perimental results show that γ-ray irradiation can improve the affinity between HDPE andSTC, and the dispersion of STC in HDPE matrix. Compared with HDPE/STC (80/20)blend, the yield stress and impact strength of irradiated HDPE (10kGy)/STC (80/20) blendare increased from 22.8 MPa and 70J/m to 28.5 MPa and 144J/m. The yield stress andimpact strength of HDPE/irradiated HDPE/STC (48/32/20) are 27.8MPa and 210J/m,respectively.     

A NEURAL NETWORK STUDY ON GLASS TRANSITION TEMPERATURE OF POLYMERS

In this paper, an atificial neural network model is adopted to study the glass transition temperature of polymers. Inour artificial neural networks, the input nodes are the characteristic ratio C_∞, the average molecular weigh M_e betweenentanglement points and the molecular weigh M_(mon) of repeating unit. The output node is the glass transition temperature T_g,and the number of the hidden layer is 6. We found that the artificial neural network simulations are accurate in predicting theoutcome for polymers for which it is not trained. The maximum relative error for predicting of the glass transitiontemperature is 3.47%, and the overall average error is only 2.27%. Artificial neural networks may provide some new ideas toinvestigate other properties of the polymers.