摘要:

AbstractThe principles of NMR imaging applicable to materials are reviewed, and examples of current developments given. Among the different types of materials, polymers are particularly suitable for NMR imaging, because they are rich in protons, the most sensitive NMR nucleus. While the spatial resolution in solid materials is restricted to dimensions larger than 50 μm, the interest in NMR as an imaging technique derives from the abundance of parameters, which can be converted to image contrast for localization and identification of material morphology, chemistry and physics. Particular progress has been achieved in imaging of polymer melts and liquids, where diffusion and non‐Newtonian flow are investigated as well as of elastomers, where composition, deterioration by thermal and mechanical aging, and stress distribution can be characteriz

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940801

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractNovel organic‐soluble lithium salts, lithium 1,1,2‐trifluoro‐4‐methoxy‐1‐butanesulfonate (I) and lithium 3‐(2‐methoxyethoxy)‐1‐propanesulfonate (II), were synthesized. Their ionic conductivities were examined in a solid polymer matrix ofendo‐methoxy oligo(oxyethylene)‐branched poly(phosphazene) (III) and compared with the ordinary hybrids of LiCIO4/III or LiSO3CF3/III. The ionic conductivity of I/III hybrid was as high as 2,2.10−5S. cm−1at 25°C, which is comparable to that of LiCIO4/III or LiSO3CF3/III hybrids. Although anions are the major carrier ions in the LiCIO4/III or LiSO3CF3/III hybrids, the lithium transport number of I/III hybrid was about 0.5 due to the larg

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940802

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractCopolymerization of ethylene with a small amount of propene was conducted with a TiCl4/MgCl2‐Al(C2H5)3catalyst system using a stopped‐flow method. With an increase in the polymerization time from 0,035 to 0,145 s, the copolymer yield increases linearly but the number‐average molecular weight of the copolymer showed a tendency of saturation. The rate constants of the propagation reaction as well as the concentrations of active sites were estimated using these data. On the other hand, the1H NMR spectra of copolymer did not display the resonances due to CC double bonds which should be formed by chain transfer with monomer and/or by β‐hydrogen elimination. It was also found that the crystallinity of the copolymer decreases to a great extent upon incorporation of even a very small quantity of propylene units. From these results, it was concluded that the apparent rate of copolymerization is not controlled by monomer diffusion through the polymer films. Rather the transfer reaction with Al(C2H5)3might predominantly take place during the copoly

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940803

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractNew terephthalic acids with aromatic substituents were prepared in two different ways. A first attempt was made by nucleophilic substitution of dimethyl nitroterephthalate with phenoxide ions. The formation of phenyl methyl ethers is a significant side reaction in this procedure. The second method consists in the arylation of dimethyl 2‐(4′‐hydroxyphenylthio) terephthalate with activated fluoroaromatics. Insufficient electrophilicity of the fluoro compound is here the limiting factor. Thermotropic polyesters were prepared from 4,4′‐biphenyldiol and various arylthioterephthalic acids. It was found that increasing length of the aromatic side chain improve both solubility and meltability. All polyesters form a nematic phase above their melting p

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940804

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractDilute solutions of poly{6‐[4‐(4‐methoxyphenoxycarbonyl)phenoxy]hexyl methacrylate} (1 a, structure‐based IUPAC name poly(1‐{6‐[4‐(4‐methoxyphenoxycarbonyl)phenoxy]hexyloxycarbonyl}‐1‐methylethylene)) were investigated by means of size‐exclusion chromatography (SEC), osmometry, light scattering, and viscometry. It was found that the universal calibration of SEC is not valid with this polymer and that dilute solution properties (intrinsic viscosity, second virial coefficient) are at variance with predictions from the two‐parameter theory of polymer solutions. The latter discordance is explained on the basis of the theory of hydrodynamic properties of wormlike chains which takes into account the effective diameter of the chain. The characteristic ratio (C∞ = 15,1) and the Kuhn segment length (λ−1= 28 · 10−8cm) were estimated. The polymer‐solvent interaction parameter was shown to decrease in the series of solvents: 1,1,2,2‐tetrachloroethane, chloroform, tetrahydrofuran,N,N‐dimethylformamide. The interaction of the solvents with the side groups w

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940805

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractCopolymers of 2‐(3‐methacryloyloxypropyl)‐4,5‐diphenyloxazole (3) with various monomers were prepared. It was observed that the oxazole rings attached to the copolymer backbone are converted efficiently to the corresponding triacylamino residues by photooxidation usingmeso‐tetraphenylporphin as a photosensitizer in solution and in a thin film of the polymer. This photoinduced transformation in a copolymer5chavingN‐isopropylacrylamide as a comonomer was found to be applicable to a positive working photoresist by development with an aqueous solution of amines to dissolve the exposed areas of the film. A new system for positive image formation by visible light i

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940806

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThis is a description of the Pd‐catalyzed synthesis of two poly(p‐phenylene) (PPP) derivatives which have butoxymethyl side groups on each, or every alternate, phenylene moiety. For the latter, details are given of the quantitative transformation of the ether functionalities into bromomethyl pendant groups. Subsequent reaction of these bromo functionalities with sodium 4‐cyanophenolate or sodium acetate produced structurally homogeneous PPP's which had 4‐cyanophenoxymethyl and acetoxymethyl side groups, respectively. The PPP derivatives described here are soluble in common organic solvents and were characterized in detail by NMR spectroscopy, membrane osmometry and size exclusion chromatography (SEC). The degrees of polycondensation of the butoxymethyl‐substituted polymers were found to be in the order of 30–65. No evidence for chain degradation during the following conversions was found on the basis of the NMR and SEC m

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940807

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe paper deals with transport functions of natural polyphosphates, i.e. wall‐and lipoteichoic acids (WTA, LTA) appearing in Gram‐positive bacteria. The results concerning the separation of magnesium and calcium ions in a membrane system, simulating bacteria cell wall, are presented. The system was composed of a solid polymer membrane and a liquid membrane, containing poly(trimethylene phosphate) and α‐hydroxy‐ω‐(2‐ethylhexyl)‐poly(trimethylene phosphate) applied as synthetic analogues of WTA and LTA, respectively. Up‐hill transport with reference towards magnesium

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940808

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe copolymerization ofN‐cyclohexylmaleimide (1) (M1) and bis(2‐ethylhexyl) itaconate (2) (M2) with dimethyl 2,2′‐azoisobutyrate (3) as an initiator was carried out at 50°C in benzene. Monomer reactivity ratios were estimated asr1= 0,34 andr2= 0,38. The copolymerization rate (Rp) and the molecular weight of the resulting copolymer increased with increasing concentration of1when the total concentration of comonomers was fixed at 1,00 mol. L−1.Rpwas proportional to [3]0,5, indicating a usual bimolecular termination in the copolymerization. An electron spin resonance (ESR) spectrum of the propagating polymer radicals was observable in the actual copolymerization system at 50°C. The spectrum of the copolymerization system is inexplicable in terms of any superposition of spectra observed in the corresponding homopolymerization systems, revealing that some penultimate monomeric unit causes a change in the ESR spectrum, that is, the structure of propagating polymer radical. The apparent rate constant of propagation (kp) and termination (kt) were estimated by ESR. Thekpvalues (1,5–50 L · mol−1· s−1) are fairly higher than those estimated on the basis of the terminal model, affording another piece of evidence for the penultimate effect. Thektvalue (1,8–5,4·103L · mol−1· s−1) shows a behaviour similar to that of the intrinsic viscosity of the resulting copolymer on varying the monomer feed composition, which seems to reflect diffusion‐co

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940809

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe microstructure of two bicomponent and one tricomponent segmented copolymers, based on polydimethylsiloxane, poly(p‐hydroxystyrene) or/and polysulfone, were investigated using an extended Goldman‐Shen pulse sequence, proton spin‐spin relaxation measurements, and13C and29Si NMR spectra. The results indicate that there exist four phases with different sizes, components and morphological structure in the segmented copolymers studied in this work, i.e., a rigid‐chain phase of very slow motion, a rigid‐chain‐rich phase of slow motion, a flexible‐chain‐rich phase of fast motion and a flexible‐chain phase of faster motion. The sizes of different domains, calculated from the spin diffusion rates, are about 50–100 Å for the flexible‐chain‐rich phase of fast motion and 200–300 Å for the flexible‐chain phase of faster motion. The relative quantities of polydimethylsiloxane in the flexible‐chain phase of fast motion are slightly different in differen

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940810

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY