A MORPHOLOGICAL STUDY OF POLY（DIVINYLBENZENE-co-ACRYLIC ACID） IN CROSSLINKING PRECIPITATION POLYMERIZATION

Divinylbenzene-80 （DVB-80） and polar monomer acrylic acid （AA） having hydrogen bonding at a total monomer loading of 5 vol% were precipitated-copolymerized in a variety of organic solvents with 2,2＇-azobis（isobutyronitrile） （AIBN） as initiator. The experiments were investigated from a two-dimensional matrix, i.e., the actual crosslinking degree of DVB varying from 0 to 80% and the solvent composition varying from 0 to 100% of toluene mixture with acetonitrile, when the mixture of acetonitrile and toluene was used as the reaction solvent. Under various reaction conditions, six distinct morphologies including soluble polymers, swellable microgels, coagulum, irregular microparticles, and nano-/micrometer microspheres were formed and the structures of these polymer architectures were described. A morphological map was utilized to discuss the effects of both crosslinking degree of DVB and composition of solvent on the transitions between morphology domains. The results demonstrated that the microspheres are formed by an internal contraction due to the marginal solvency of the continuous phase and the crosslinking of the polymer network through the covalent bonding from DVB as well as the interchain hydrogen-bonding between the carboxylic acid units.     

POLYMER NETWORK-POLY(ETHYLENE GLYCOL)COMPLEXES WITH SHAPE MEMORY EFFECT

The complexes of poly(methacrylic acid-co-methyl methacrylate) network with poly(ethylene glycol) stabilized byhydrogen bonds were prepared. By introducing the poly(ethylene glycol), a large difference in storage modulus below andabove the glass transition temperature occurred and the complexes exhibited shape memory behaviors. The morphology ofcomplexes was studied by using DSC, WAXD, and DMA. The results indicate that the fixed phase of this kind of novelshape memory materials is the network, and the reversible phase is the amorphous state of PEG:PMAA complex phase. Theshape recoverability almost reaches 100%. This type of complexes can be regarded as a novel shape memory network.     

Practical capillary gas chromatography—a systematic approach

Capillary gc is now rapidly expanding. Naturally, initiation is most often attempted on the basis of the experience acquired with packed columns. However, such an extrapolation is successful only if a number of essential peculiarities of capillary gc are considered. Based on practical examples this paper discusses six essential details: 1) design and maintenance of the gas flow paths, 2) the greatly increased importance of sampling technique, which should not be confined just to stream splitting, 3) the problems in quantitative analysis arising from small sample size, 4) specific sources of trouble related to small amounts of liquid phase, 5) specific arguments for the choice of the carrier gas, clearly pointing to hydrogen as the ideal carrier and, 6) the different way to approach column production. Figures for all selected examples are given.     

Synthesis and Crystal Structure of Lithium Tetrametaphosphimate Tetrahydrate Li4(PO2NH)4 · 4 H2O

Single crystals of Li₄(PO₂NH)₄ · 4 H₂O were obtained by dissolving LiOH and H₄(PO₂NH)₄ · 2 H₂O in water and subsequent precipitation with acetone and ethanol followed by slow evaporation of the solvents. The structure of Li₄(PO₂NH)₄ · 4 H₂O was solved by single‐crystal X‐ray methods ( (No. 2), a = 489.2(2), b = 853.2(2), c = 880.5(2) pm, α = 101.71(3), β = 102.39(3), γ = 94.88(3)°, Z = 1). The structure is composed of LiO₄ tetrahedra and (PO₂NH)₄^4? ions. The P₄N₄ rings of the anions exhibit a slightly distorted chair–1 conformation, which is supported by IR data and has been described by torsion angles, displacement asymmetry parameters and puckering parameters. Via Li⁺ ions and hydrogen bonds, the tetrametaphosphimate anions are connected forming a three‐dimensional network.     

High-Resolution Infrared Synchrotron Investigation of (HCN)2 and a Semi-Experimental Determination of the Dissociation Energy D0

The high-resolution infrared absorption spectrum of the donor bending fundamental band ν of the homodimer (HCN)₂ has been collected by long-path static gas-phase Fourier transform spectroscopy at 207 K employing the highly brilliant 2.75 GeV electron storage ring source at Synchrotron SOLEIL. The rovibrational structure of the ν transition has the typical appearance of a perpendicular type band associated with a Σ–Π transition for a linear polyatomic molecule. The total number of 100 assigned transitions are fitted employing a standard semi-rigid linear molecule Hamiltonian, providing the band origin ν₀ of 779.05182(50) cm⁻¹ together with spectroscopic parameters for the degenerate excited state. This band origin, blue-shifted by 67.15 cm⁻¹ relative to the HCN monomer, provides the final significant contribution to the change of intra-molecular vibrational zero-point energy upon HCN dimerization. The combination with the vibrational zero-point energy contribution determined recently for the class of large-amplitude inter-molecular fundamental transitions then enables a complete determination of the total change of vibrational zero-point energy of 3.35±0.30 kJ mol⁻¹. The new spectroscopic findings together with previously reported benchmark CCSDT(Q)/CBS electronic energies [Hoobler et al. ChemPhysChem. 19 , 3257–3265 (2018)] provide the best semi-experimental estimate of 16.48±0.30 kJ mol⁻¹ for the dissociation energy D₀ of this prototypical homodimer.     

醇和N,N-二甲基乙酰胺分子间相互作用的FTIR光谱研究

The association between alcohols and N,N-dimethylacetamide in carbon tetrachloride was investigated using FTIR spectroscopy at 298 K.The formation constants for 1∶1 and 1∶2 complexes were calculated using the method of Whetsel and Kagarise.The observed 1∶1 complex values were also verified using the method of Nash.The rate of change in C=O bond moment on complexing with alcohols increased with increasing acidity of alcohols.The formation constant and values of free energy change increased with the increase in carbon chain length of alcohols,which suggested that the degree of complex formation varied with the length of the carbon chain of alcohols.     

Syntheses of DL-threo-Thiamphenicol via Green Oxidation

IntroductionAqueous hydrogen peroxide is considered to be a“green”oxidant with a high oxidation efficiency due toits low molecular weight,cleanness in the oxidationprocess in which only harmless water is produced,lowcost of production and safe transport…     

Analytical techniques for cyanide in blood and published blood cyanide concentrations from healthy subjects and fire victims

Hydrogen cyanide can be produced by the pyrolysis of man-made polymers. Cyanide has been measured in the blood of healthy adults as well as the blood of fire survivors and fatalities. In healthy subjects the blood cyanide concentration of smokers is higher than that of non-smokers. Fire survivors and fatalities have been found to have higher cyanide levels than of control groups and the levels from fire fatalities are often higher than survivors. Blood concentrations quoted as normal, toxic or fatal are highly variable in the literature. Many studies have been performed to measure the blood cyanide levels in control subjects as well as those who have been exposed to fire but the values found differ. The values for control subjects can vary from none detected to 19 μmol dm⁻³ while those for fire survivors range from not detected to 150 μmol dm⁻³ and fatalities range from not detected to 284 μmol dm⁻³. Analytical techniques and published data are critically reviewed.Many of the existing antidotes for cyanide poisoning are highly toxic themselves and should ideally be administered at doses proportional to the amount of cyanide a patient has received to avoid compounding damage done by cyanide intoxication. For this reason, a rapid, accurate bedside assay of blood cyanide concentration that differentiates between bound and free cyanide would represent a leap forward in the clinical management of cyanide poisoning.     

Electron‐Transfer Mediator Microbiosensor Fabrication Based on Immobilizing HRP‐Labeled Au Colloids on Gold Electrode Surface by 11‐Mercaptoundecanoic Acid Monolayer

In this paper, a new strategy for constructing a mediator‐type amperometric hydrogen peroxide (H₂O₂) microbiosensor was described. An electropolymerized thionine film (PTH) was deposited directly onto a gold electrode surface. The resulting redox film was extremely thin, adhered well onto a substrate (electrode), and had a highly cross‐linked network structure. Consequently, horseradish peroxidase (HRP) was successfully immobilized on nanometer‐sized Au colloids, which were supported by thiol‐tailed groups of 11‐mercaptoundecanoic acid (11‐MUA) monolayer covalently bound onto PTH film. With the aid of the PTH mediator, HRP‐labeled Au colloids microbiosensor displayed excellent electrocatalytical response to the reduction of H₂O₂. This matrix showed a biocompatible microenvironment for retaining the native activity of the covalent HRP and a very low mass transport barrier to the substrate, which provided a fast amperometric response to H₂O₂. The proposed H₂O₂ microbiosensor exhibited linear range of 3.5 μM–0.7 mM with a detection limit of 0.05 μM (S/N=3). The response showed a Michaelis‐Menten behavior at larger H₂O₂ concentrations. The K_M^app value for the biosensors based on 24 nm Au colloids was found to be 47 μM, which demonstrated that HRP immobilized on Au colloids exhibited a high affinity to H₂O₂ with no loss of enzymatic activity. This microbiosensor possessed good analytical performance and storage stability.     

Ion pairing, H-bonding, and π–π interactions in copper(II) complex-organo-networks derived from a proton-transfer compound of the 1,10-phenanthroline-2,9-dicarboxylic acid

The one-pot reaction between the novel proton transfer compound (pydaH₂)²⁺(phendc)²⁻, LH₂, and Cu(II) afforded the compounds (pydaH)₂[Cu(phendc)₂]·10H₂O, 1, and (pydaH)₂[Cu(phendc)(phendcH)]₂·5H₂O, 2, where pyda=2,6-diaminopyridine, and phendcH₂=1,10-phenanthroline-2,9-dicarboxylic acid. The single crystal X-ray diffraction analysis of 1 and 2 revealed that these are two novel self-assembled 3D Cu(II) complex-organo-networks, in which (pydaH)⁺ ions and [Cu(phendc)₂]²⁻ or complex units are held together by ion pairing, H-bonding, and π–π interactions. Magnetic measurements over the temperature range 1.8–310 K revealed no significant magnetic coupling between Cu(II) centers in 1 or 2.