Isolation, spectra, structure, and ring-opening polymerization of strained macrocyclic aryl(ether ketone) dimer

Macrocyclic arylene ether ketone dimer was isolated from a mixture of cyclic oligomers obtained by the nucleophilic substitution reaction of bisphenol A and 4,4'-difluorobenzophenone and easily polymerized to high molecular weight linear poly(ether ketone). The cyclic compound was characterized by FTIR, H-1- and C-13-NMR, and single-crystal x-ray diffraction. Analysis of the spectral and crystal structure reveals extreme distortions of he phenyl rings attached to the isopropylidene center and of the turning points of the molecular polygons. The release of the ring strain on ring-opening combined with entropical difference between the linear polymer chain and the more rigid macrocycle at temperatures of polymerization may be the proposed motivating factors in the polymerization of this precursor to high molecular weight poly(ether ketone). (C) 1997 John Wiley & Sons, Inc.

Abnormal IR spectra of CO adsorbed on the surface of glass carbon electrode modified with polypyrrole film with platinum microparticles

Abnormal IR spectra of CO adsorbed at the surface of glass carbon electrode modified with polypyrrole film with Pt microparticles are reported.

Effect of urea on synchronous fluorescence spectra and electrochemical behaviour of cytochrome c

The changes of the synchronous fluorescence spectra and the electrochemical behaviour of cytochrome c with the urea concentration are studied. It has been found that with the increase of urea concentration, there occur sequentially the deaggregation of cytochrome c molecules, the increase of exposure extent of the heme group to the solvent, the disruption of Fe-S bond of the heme group and the change in the electrochemical behaviour of cytochrome c. It is suggested that the reason why the electrochemical reaction of cytochrome c is irreversible is that cytochrome c molecules exist in the concentrated solution as oligomers which are electrochemically inactive.

The phase transitions of hetero atoms substituted molecular sieves Me-VPI-5(Me=Mg, Ti, Sn, Si) and their influence on spectra structures of Eu(III) ion

The hetero atom substituted aluminophosphate molecular sieves Me-VPI-5(Me = Mgt Ti, Sn, Si) were synthesized hydrothermally. Rare earth ions are originally doped into these microporous materials by aqueous solution ion exchange procedures. The phase transitions of the microporous materials are investigated by high-temperature and high-pressure experimental techniques. The influence of the phase transitions on the rare earth ions' spectral structures is discussed, With the increase of temperature, Eu(II)Mg-VPI-5 is converted into Eu(II)Mg-AIPO(4)-8, then into tridymite phase. The pressure has a notable influence on Eu(II) ion's spectral structures. The spectral structures have changed regularly with the increase of pressure.

NMR Spectra of polyimides: Interpretation and local chain motion study

Three kinds of high-performance polyimides 1 (poly(ketone-imide) PKI), 2 (poly(ether-imide) PEI) and 3 (poly(oxy-imide) POI) were studied using nuclear magnetic resonance (NMR). The NMR spectra of the polyimides were assigned according to the comprehensive consideration of the substitution effect of different substituting groups, viz. distortionless enhancement by polarization transfer (DEPT), no nuclear Overhauser effect (NNE), analysis of relaxation time, and two-dimensional correlated spectroscopy (COSY) techniques. The structural units of these three polyimides were determined. Carbon-13 and proton relaxation times for PEI and PKI were interpreted in terms of segmental motion characterized by the sharp cutoff model of Jones and Stockmayer (JS model) and anisotropic group rotation such as phenyl group rotation and methyl group rotation. Correlation times for the main-chain motion are in the tens of picosecond range which indicates the high flexibility of polyimide chains. Correlation times for phenyl group and methyl group rotations are more than 1 order of magnitude lower and approximately 1 order of magnitude higher than that of the main chain, respectively.

THE EFFECT OF SOLUTION PH ON SYNCHRONOUS FLUORESCENCE-SPECTRA OF CYTOCHROME-C SOLUTIONS

Synchronous fluorescence spectra of cytochrome c solutions were studied. It was found that synchronous fluorescence spectra of tyrosine and tryptophan residues in cytochrome c molecules can be separated using different wavelength intervals. The changes in synchronous fluorescence spectra of cytochrome c solutions with the solution pH are different from that of free tyrosine and tryptophan and reflect the pH-induced conformational transitions of cytochrome c molecules. (C) 1995 Academic Press, Inc.

SYNTHESIS OF A NEW CHIRAL LIQUID-CRYSTAL WITH SCHIFF-BASE GROUP AND INVESTIGATION OF TEMPERATURE-DEPENDING FTIR SPECTRA

A new chiral liquid crystal with Schiff base group has been prepared, The structure of liquid crystal was confirmed by elementary analyses and H-1 NMR. Its phase transition was investigated by polarized optical microscope, DSC and temperature-depending FTIR spectra. The results showed that the chiral Schiff base showed monotropic phases behavior in certain temperature range, the phase sequence is I-N-*-S-B-S-G-K on the cooling sequence.

PREPARATION, CRYSTAL-STRUCTURE, AND VIBRATIONAL-SPECTRA OF PEROVSKITE-TYPE MIXED OXIDES LAM(Y)M'(1-Y)O(3) (M,M'=MN, FE, CO)

Three series of samples LaMnyCo1-yO3+/-lambda, LaFeyMn1-yO3+/-lambda, and LaFeyCo1-yO3+/-lambda (y = 0.0 to 1.0) with Perovskite structure were prepared by an explosion method different from the generally used ceramic techniques. The variation of crystal

CRYSTAL-STRUCTURE AND INFRARED-SPECTRA OF A LANTHANUM COORDINATION COMPOUND WITH GLYCINE, ([LA(GLY)S-CENTER-DOT-2H2O]CENTER-DOT(CLO4)3)N

A lanthanum coordination compound with glycine {[La(Gly)3.2H2O].(ClO4)3}n (Gly = NH+ 3-CH2-COO-) was synthesized and obtained in the form of single crystals. Its X-ray crystal structure has been determined and the IR spectrum has been studied. Crystallo

CRYSTAL-STRUCTURES AND MOSSBAUER-SPECTRA OF LAFE1-XMNXO3 AND LAFE1-XCOXO3 (X=0 TO 0.9)

The crystal structures and Mossbauer spectra of various mixed oxides LaFe1-xMnxO3 and LaFe1-xCoxO3 (x = 0 to 0.9) are determined and measured at room temperature. The results indicate that the crystal structure of both the La-Fe-Mn-O and the La-Fe-Co-O sy

A STUDY OF CHARGE SEPARATION AND ELECTRON-CAPTURE INDUCED DECOMPOSITION SPECTRA OF PHENYLENEDIAMINE ISOMERS

The structures and decomposition reactions of doubly charged phenylenediamines were studied by means of charge separation (CS) and electron capture induced decomposition (ECID) spectra. The deisomerization of the three isomers is prior to the metastable d

THE VALENCY AND SPECTRA OF SAMARIUM IONS IN MF(2)-MGF2 (M=CA, SR, BA)

The phosphors MMgF(4)(M = Ca, Sr, Ba) doped with samarium ions are synthesized in different atmospheres using solid phase reaction at high temperature. Samarium has been first stabilized in the divalent state in SrMgF4 and BaMgF4 matrices. Effects of matrices on the valent state of samarium ions are briefly discussed.

INFRARED-SPECTRA OF DIMETHYLPHOSPHATE LANTHANIDE COMPLEXES

The infrared spectra of the crystalline solid samples of rare earth(III) dimethylphosphates Ln(DMP)3 (Ln = La, Ce, Nd) in the range 4000-100 cm-1 are discussed. It is shown that the spectra may be treated by dividing Ln(DMP)3 into two parts, an OP(OCH3)2O bridge and a LnO6 distortion octahedron. The absorption bands above 500 cm-1 may be clearly assigned. However, vibrational assignments in the far-infrared region are tentative.

X-RAY PHOTOELECTRON-SPECTRA OF SOME BIOINORGANIC COMPLEXES OF THE RARE-EARTHS WITH N-ACETYLALANINE

X-Ray photoelectron spectra of some bioinorganic complexes of La, Ce, PT, Nd, Sm and Eu with N-acetylalanine have been measured and the 3d5/2 and 3d3/2 main peaks and their satellites have also been assigned. ne spin-orbit splitting between the 3d5/2 and 3d3/2 core-level of the rare earth ion in these complexes becomes slightly larger than that of the free rare earth atom due to the effect of the crystal field. The satellite for the 3d main peaks of La in the solid state complex are in higher binding energy region and may be attributable to the L --> 4f charge-transfer shake-up process. The satellites for the 3d main peaks of Ce, Pr, Nd, Sm and Eu are in the lower binding energy region and may be attributable to the 4f --> L charge-transfer shake-down process.