STUDIES ON THE KINETICS OF PHOTOPOLYMERIZATION OF ACRYLONITRILE INITIATED BY ANILINE

The dependence of the rate of polymerization on the aniline concentration in the photopolymerization of acrylonitrile initiated by aniline was studied.The rate of polymerization of acrylonitrile increased with increasing of the aniline concentration and showed a maximum at first, then showed another increase after a minimum.This phenomenon was explained with the extinction coefficient of aniline at 313 nm,334 nm and 365 nm wavelengths.Similar results were obtained for the aniline derivatives.Therefore, the initiator exponents in the photopolymerization varies with the different concentrations of initiator and the square-root dependence can be obtained only at certain low concentrations, i.e. with low absorbance.     

TEMPERATURE—DEPENDENCE OF CARRIER ION NUMBER IN SOLID POLYETHER MEDIA

The temperature—dependence of cationic conductivity,mobility andcarrier generation in the blend of macromolecular lithium salt and copoly-ether were investigated.The population of free—ions was found to decreaseexponentially with rising temperature.However,this“anomalous”behavior ofsalt—dissociation has little effect on the temperature—dependence of con-ductivity,since it is ion mobility rather than carrier ion number whichpredominates ion transport process.     

STUDY OF THE MAGNETIC PROPERTIES OF LaGa_(1-x)Fe_xO_3

The dependence of the susceptibitity of LaGA_(1-x)Fe_xO_3(x=0.2,0.5,6.8) on the concentration of Fe~(3+),teperature and magnetic fietdintensity were studied and the change of Neet point was observed.Some regularities were obtained for first time in this paper.     

Helical twisting properties of new chiral dopants with double (S)-1, 2-propanediol units for nematic liquid crystals

<正>A novel series of chiral dopants synthesized from(S)-1,2-propanediol and mesogenic carboxylic acids were characterized by FT-IR,~1H NMR,elemental analysis and their helical twisting properties were investigated by doping the chiral dopants into a nematic liquid crystal host(SLC-1717).The results show that,the helical pitch of N~*-LC mixture exhibited a terminal alkyl chain length dependence and the molecular twisting power β also exhibited a temperature dependence(increasing β with increasing temperature).     

DIRECT ELECTROCHEMICAL BEHAVIOUR OF CYTOCHROME C AT A BARE GLASSY CARBON ELECTRODE

A reversible electron transfer between horse heart cytochrome c and a bare glassy carbon electrode was found and the dependence of direct electrochemical behaviotw on the electrode surface state was discussed.     

Luminescence and energy transfer of Ce~(3+) and Dy~(3+) in BaLaB_9O_(16)

Under the excitation of UV light, the composition dependence of luminescence properties of Ce3+ and Dy3+ in BaLaB9O16 has been studied. The mechanisms of energy transfer from Ce3+ to Dy3+ and of concentration quenching of Dy3+ emission under the excitation of UV light have been presented as well.     

New insights into the effects of molecular weight and end group on the temperature-induced phase transition of poly(N-isopropylacrylamide) in water

In an attempt to clarify issues related to the molecular weight dependence of the phase transition of poly(N-isopropylacrylamide) (PNIPAM) in water,we prepared a library of PNIPAM samples of well-controlled molecular weight (7000 to 45000 g/mol) bearing identical groups on each chain end.The polymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) with a bifunctional chain tranfer agent and further end group modification.The effects of the end group chemical structure,hydroxyethyl (HE),propargyl (Pr),chloroethyl (CE),n-butyl (nBu),n-hexyl (nHe),and isobutylsulfanylthiosulfanyl (IBS) on the phase transition temperature of aqueous PNIPAM solutions were investigated by high-sensitivity differential scanning calorimetry (HS-DSC),yielding the enthalpy ΔH and the endotherm maximum temperature (T M),and turbidimetry,providing the cloud point (T CP) of each solution.The T CP and T M of the PNIPAM sample of lowest molar mass (M n 7,000 g/mol,0.5 g/L) ranged,respectively,from 38.8 to 22.5 °C and 42.2 to 26.0 °C,depending on the structure of the end-group,whereas H showed no strong end-group dependence.The phase transition of all polymers,except,-di(n-butyl-PNIPAM),exhibited a marked dependence on the polymer molar mass.     

MEASUREMENT METHOD AND PHYSICAL MODEL OF VSC CONDUCTIVITY AND ITS APPLICATIONS IN CONDUCTING POLYMERS

Method of VSC (Voltage Shorted Compaction)can be used to determine the intrinsic temperature dependence ofconductivity ofpolycrystalline compaction. The experimental conditions and technical key for preparation of VSC device and its physical model as well as its applications in conducting polymers are discussed in detail.     

EXPERIMENTAL CHARACTERIZATION OF FLUOROCARBON-MODIFIED POLYACRYLAMIDE/SURFACTANT AQUEOUS SOLUTIONS

The interaction between surfactants and fluorocarbon-modified polyacrylamide (FC-PAM) in aqueous solutionswas evaluated by rheological means and fluorescence spectroscopy and was found to be strong regardless of the surfactant'snature. Two representative surfactants, anionic sodium dodecyl sulfate (SDS) and nonionic Triton X-100, were used. The origin of the interaction and its dependence on the surfactant concentration were discussed.     

GAS PERMEATION OF SEGMENTED POLYURETHANES AND THEIR BLENDS WITH PVC

Film specimens of four segmented polyurethanes with different soft segments, namely polycaprolactone, polytetramethylene adipate, polytetramethylene oxide and polypropylene oxide, and their blends with PVC of different compositions were obtained by solution cast. The permeability of these films to O_2, N_2 and H_2 and their density were measured by using gas chromatography and technique of density gradient column. The polyether polyurethanes were found to have higher permeability than the polyester ones due to their low glass transition temperature and /or the low density value. The blends of PVC and polyether polyurethanes, especially the PPO-based polyurethane, are incompatible, and their permeability coefficient-composition dependence has the typical S-shaped curves. PVC is well compatible with the soft segments in its blends with polyester polyurethanes. For these blends the composition dependence of permeability is characterized by a negative deviation from the semilogarithmic additivity rule, and it is possible to prepare blends having T_g 20℃lower than that of PVC, but retaining its low permeability almost unchanged, results were discussed in according with the different approaches for the permeation behavior of compatible and incompatible blends.     

四氟乙烯齐聚体的反应 四氟乙烯四、五聚体和芳香胺的反应

前已报道四氟乙烯四聚体(全氟-3,4-甲基己烯-3)(1)、五聚体(全氟-3,4-二甲基-4-乙基己烯-2)(2)和脂肪烷氧以及脂肪胺的亲核反应.本文报道化合物1,2和芳香胺如苯胺、β-萘胺的反应.由于烯烃1、2双键处于分子中间,因而当亲核试剂进攻时,双键容易发生重排,生成的末端基烯烃更具反应性,故导致一取代、二取代、三取代以及环化降解等复杂产物.     

分子动力学模拟研究纳米碳管中甲醇-水混合溶液的结构与输运性质

利用分子动力学模拟方法,对比考察了平衡条件、外压作用、梯度电场作用下,摩尔比为1:1的甲醇-水混合溶液在纳米碳管(CNT)中的静态结构以及输运行为.研究发现:在平衡体系与外压作用下,纳米碳管内甲醇与水呈现出明显的不混溶现象,甲醇主要分布于管壁附近,水分子主要分布于纳米碳管轴心附近;而在梯度电场作用下,纳米碳管由疏水性向亲水性转变,更多的水分子分布于管壁,导致纳米碳管内甲醇-水的不混溶现象消失.另一方面,在外压作用下,纳米碳管内甲醇与水呈现单向移动;而在梯度电场下,甲醇与水呈现快速的双向移动,其流通量较相应外压作用体系高出近一个数量级,但由于双向的流通量大小相近,导致净流通量与外压作用下的净流通量差异不大.     

STUDY ON A HYDROPHOBIC-HYDROPHILIC GRADIENT ROD

INTRODUCTIONGradient materials constitute a special case of various materials. The concentration of one of the components ofthe material, being chemically and/or physically different from other components, is allowed to change as afunction of its position in the sample, producing a predetermined gradient profile. The gradient material can be inany shape — i.e., linear, sigmoid, parabolic, flat or rod. Generally, this kind of material should have gradientsalong one direction in their stru…     

BAB‐random‐C Monomer Sequence via Radical Terpolymerization of Limonene (A), Maleimide (B), and Methacrylate (C): Terpene Polymers with Randomly Distributed Periodic Sequences

A naturally abundant terpene, limonene (A), was radically polymerized with a maleimide derivative (B) and methacrylate (C) in a fluorinated alcohol to give terpolymers with unprecedented BAB‐random‐C sequences in which the BAB monomer sequence was randomly copolymerized with a C unit. In each binary system, limonene was hardly copolymerized with methacrylate while it was efficiently copolymerized with maleimide to result in a 1:2‐alternating BAB periodic sequence, in part due to the penultimate effects and hydrogen‐bonding interactions with fluoroalcohol. Methacrylate and maleimide were randomly copolymerized to give copolymers rich in methacrylate units with minimal amounts of maleimide–maleimide sequences. Their terpolymerization resulted in a BAB‐r‐C sequence as a consequence of the selective BAB polymerization between limonene and maleimide, the random copolymerization between methacrylate and maleimide, and the lack of copolymerization between limonene and methacrylate.     

Electrochemical Detection Using an Engraved Microchip – Capillary Electrophoresis Platform

The present study describes a simple strategy to integrate electrochemical detection with an assembled microchip‐capillary electrophoresis platform. The electrochemical cell was integrated with a microfluidic device consisting of five plastic squares interconnected with fused silica capillaries, forming a four‐way injection cross between the separation channel and three side‐arms (each of 15 mm in length) acting as buffer/sample reservoirs. The performance of the system was evaluated using electrodes made with either carbon ink, carbon nanotubes, or gold and under different experimental conditions of pH, capillary length, and injection time. Using this system it was possible to separate the neurotransmitters dopamine and cathecol and to quantify phenol from a real sample using a linear calibration curve with a calculated LOD of 0.7 µM. A similar concept was applied to determine glucose, by including a pre‐reactor filled with beads modified with glucose oxidase (GOx). The latter system was used to determine glucose in a commercial sample, with a recovery of 95.2 %. Overall, the presented approach represents a simple, inexpensive, and versatile approach to integrate electrochemical detection with CE separations without requiring access to microfabrication facilities.     

Ring-opening cross-metathesis (ROCM) as a novel tool for the ligation of peptides

The development of ring-opening cross-metathesis (ROCM) as a novel tool for the site-specific ligation of peptide units is reported. The resulting structural units at the site of ligation resulting from ROCM resemble proline as well as other known beta-turn stabilising structural units. ROCM under mild reaction conditions between a variety of peptides bearing a cyclic olefin with amino acids or peptides results in high yields. The peptidic cross-partners for metathesis are equipped with double bonds via the N and the C terminus and the side chain, respectively, to allow the synthesis of linear as well as non-linear and branched peptides. The ligation in this manner succeeds with low catalyst loadings, with no need for any excess of one reaction partner and with a high compatibility with a wide range of functional groups. Furthermore, the stereochemical outcome of the ROCM can easily be controlled by using a Hoveyda-type chiral catalyst. Fluorescence labelling of peptides is possible in the same manner when using a cyclic olefin equipped with a fluorescence marker.     

Comparison of modifiers for determination of arsenic, antimony and selenium by atomic absorption spectrometry with atomization in graphite tube or hydride generation and in-situ preconcentration in graphite tube

The study was performed to compare the effect of magnesium modifier (magnesium nitrate) with that of other modifiers (palladium nitrate and nickel nitrate) in determination of arsenic, antimony and selenium by atomic absorption spectroscopy with atomization in a graphite tube, with generation of hydrides and in situ preconcentration in a graphite tube. The assumed criterion of a modifier performance was the magnitude of the analytical signal. It was found that in determinations with atomization in a graphite furnace the effects of all these modifiers were comparable, while in those with hydride generation and in situ preconcentration in a graphite tube the magnesium modifier showed poorer performance (25% decrease of the analytical signal). In determinations of arsenic and selenium the analytical signal obtained with magnesium salt as a modifier was comparable with those obtained in the presence of all other modifiers.     

On the Donor Ability of the Phosphaneiminato Substituent and Cube Formation with Transition Metal Fragments

The particular role of the phosphaneiminato ligand as a donor is investigated for a) nitrenes (phosphinidenes) and carbenes and b) cubane formation with transition metals. Accordingly, and as shown for the case a) the ligand is a stronger π‐donor than an amino group and can be considered as a special case of imine‐type substituents. The latter are very effective in π‐donation. In the case b), i.e. the cubane formation with transition metals, one has to consider transition metals with a partially or completely filled d‐shell (with electrons). Hence depending on the transition metal, cubanes are build with weak ferromagnetic coupled or closed shell systems. For the cubanes with closed shell character the matter of insertion of halide anions is discussed. In the last chapter of the review the bond stretching in the dithionitrosyl complexes with rhenium is characterized.     

Serenity: A subsystem quantum chemistry program

We present the new quantum chemistry program Serenity . It implements a wide variety of functionalities with a focus on subsystem methodology. The modular code structure in combination with publicly available external tools and particular design concepts ensures extensibility and robustness with a focus on the needs of a subsystem program. Several important features of the program are exemplified with sample calculations with subsystem density‐functional theory, potential reconstruction techniques, a projection‐based embedding approach and combinations thereof with geometry optimization, semi‐numerical frequency calculations and linear‐response time‐dependent density‐functional theory. © 2018 Wiley Periodicals, Inc.     

Determination of cholesterol and triglycerides in serum lipoproteins using flow field-flow fractionation coupled to gas chromatography-mass spectrometry

Asymmetric flow field flow fractionation (AsFlFFF) was combined with pyrolysis-gas chromatography mass spectrometry for a sized based fractionation and a detailed compositional study of the triglycerides and cholesterol associated with the various lipoprotein subclasses present in human serum. Serum samples were injected in the AsFlFFF instrument and fractionated with a time-delayed exponential decay cross flow program. The fractions collected after AsFlFFF elution were injected into a programmable temperature vaporizer (PTV) GC-injector, containing a fritted liner. A temperature and split-flow program for the PTV injector was optimized for the thermally assisted hydrolysis and methylation of the compounds of interest. The resulting fatty acid and cholesterol methyl esters were separated by GC and characteristic fragment ions were detected by MS. The system was optimized and calibrated with triglyceride and cholesterol standards for quantitative analysis. The possible interference by phospholipids with the quantitative results was investigated and found to be of minor importance.The concentrations and lipoprotein profiles of triglycerides and cholesterol were determined in a pooled serum sample of healthy volunteers and a serum sample of a sepsis patient. The results obtained with the GC–MS approach were compared with those of a previously developed method based on AsFlFFF with a dual enzymatic reaction detection system. A good agreement of the profiles was found, for cholesterol as well as for the triglycerides, even when the GC–MS method quantifies the fatty acids while with the enzymatic reaction method the glycerol concentrations are determined. Total cholesterol and triglyceride concentration values for the serum samples showed good agreement with the results of the standard enzymatic method as used in practice in the university hospital.