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  • Polymer and Materials Science  (80)
  • 1990-1994  (64)
  • 1970-1974  (16)
  • 1925-1929
  • 1
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental study shows that spark energy transfer mechanisms are different for the explosive alone (HMX) and for the explosive containing 1% of graphite. This study is completed by literature data and underlines the need for parametric studies by systematically varying the electrodes gap as well as the spark duration to determine the true minimum value of the ignition energy. Grain size and shape are very important factors. The influence of the electrode shape is also discussed, as well as the environmental conditions. These data allow us to determine the conditions for testing the electric spark sensitivity of solids. The tests are then performed at a small scale.Moreover, for ionic solids or substances made of an electrically insulating matrix containing conductive inclusions, particular phenomena appear when they are submitted to electric fields for a certain time. These phenomena justify the development of specific tests to determine the capacitive discharge sensitivity.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New methacrylic copolymers with prospective second-order nonlinear optical effects are synthesized by radical copolymerization of methyl methacrylate with conjugated zwitterionic methacrylate monomers (2,6-di-tert-butyl-4-[1-(ω-methacryloyloxyalkyl)-4-pyridino]phenolates,1a and 1b). These monomers are obtained via a multi-step reaction. First, 4-(3,5-di-tert-butyl-4-hydroxyphenyl)pyridine (2) is electrosynthesized by an SRN1 reaction in liquid ammonia. Then, this pyridine derivative is N-alkylated by an ω-bromoalkyl methacrylate (5a or 5b) which, in its turn, is obtained by esterification of an ω-bromoalcohol and methacryloyl chloride.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymers and copolymers based on the monomethacryloyl ester and the vinylbenzyl ether of sucrose, bearing either blocked or free hydroxyl groups, were synthesized in the presence of free-radical catalysts, and their structures and dimensions were characterized. A range of copolymers of styrene and O-methacryloylsucrose was prepared. Reactivity ratios of the comonomers were calculated by the extended Kelen-Tüdős method. The influence of the hydroxyl groups of the sucrose moiety on the thermomechanical properties was assessed by comparing the glass transition temperatures of both blocked and unblocked copolymers. Their solubility characteristics were also determined, and it was shown that the hydrophilic-hydrophobic properties can be controlled by the amount of sucrose methacrylate in the copolymer.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The reduced viscosity ηsp/c of dilute solutions of carboxymethylcelluloses (CMC) was studied, keeping the total ionic strength of the solution constant; the variation of ηsp/c with concentration is often linear and the Huggins constant k′ increases with decreasing ionic strength. So it is possible to obtain the intrinsic viscosity [η]I = 0 at zero ionic strength I and to calculate the corresponding molecular dimensions. The variation of [η]I = 0 with the degree of substitution of CMC is explained by a progressive change from a zig-zag conformation to a rod when the linear charge of the polyion increases.
    Notes: La viscosité réduite ηsp/c des solutions diluées de carboxyméthylcelluloses (CMC) a été étudiée en gardant constante la force ionique totale de la solution; la variation de ηsp/c avec la concentration est alors souvent linéaire et la constante de Huggins k′ est d'autant plus élevée que la force ionique est faible. Il est ainsi possible d'obtenir la viscosité intrinsèque [η]I = 0 à force ionique I nulle et de calculer les dimensions moléculaires correspondantes. La variation de [η]I = 0 avec le degré de substitution des CMC s'interprète par un passage progressif d'une conformation en zig-zag à celle d'un bâtonnet lorsque la charge linéaire du polyion augmente.
    Additional Material: 10 Ill.
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bei der durch Zn(C2H5)2/H2O, Zn(C2H5)2/CH3OH, Al(C2H5)3/H2O und andere Systeme initiierten Polymerisation von N,N-Diäthyl-N-(oxiran-2-ylmethyl)amin (Ia) erhält man nur niedermolekulare polymere in geringer Ausbeute. Das entsprechende Thiiranderivat N,N-diäthyl-N-(thiiran-2-ylmethyl)amin (IIa), gibt mit demselben Initiator Hochpolymere, die nicht kristallin sind, im Gegensatz zu Propylensulfid. Physikalisch-chemische Eigen-schaften (UV-, IR-Spektren, Neutralisation und Gelbindung bei der Neutralisation) wurden untersucht. Höhere Homologe von IIa, die sich von racemischen sec-Aminen R1R2NH ableiten, werden synthetisiert und mit Zn(C2H5)2/H2O polymerisiert. Der Einfluß von R1 und R2 auf die physikalischen und chemischen Eigenschaften der Polymeren wird diskutiert.
    Notes: The polymerization of N,N-diethyl-N-(oxirane-2-ylmethyl)amine (Ia), by initiator systems such as ZnEt2/H2O, ZnEt2/CH3OH, AlEt3/H2O, and others, gives only low molecular weight polymers with low yields. The corresponding thiirane derivative, N,N-diethyl-N-(thiirane-2-yl-methyl)amine (IIa), with the same type of initiators gives high molecular weight polymers which are non-crystalline contrary to the case of propylene sulfide. Physicochemical properties (UV and IR absorptions, neutralization and gelation during neutralization) of these polymers are studied. Higher homologues of IIa derived from racemic secondary amines R1R2NH are synthesized and polymerized with ZnEt2/H2O. The influence of the substitu ents R1 and R2 on the physical and chemical properties of the polymers is discussed.
    Additional Material: 5 Ill.
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  • 7
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic properties of a styrene (S)-methyl methacrylate (MMA) diblock copolymer in semidilute solutions of toluene have been investigated by quasi-elastic light scattering. One relaxation mode has been found in the low-concentration regime near the overlap concentration C*. This mode is identified as the cooperative mode which is observed in semidilute solutions of the equivalent polystyrene (PS) homopolymer. A second mode appears simultaneously at higher concentrations. This slower diffusive mode is ascribed to the diffusion of the center of mass of the clusters formed by the copolymer molecules. The fast structural mode which is predicted by the theory1-3 is not observed. It is suggested that this mode, which must have a small amplitude, is hidden by the other two relaxation modes.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of novel telechelic monodispersed diols produced from the radical monoaddition of an excess of 10-undecenol with novel α, ω-dithiols, initiated by peroxides, is presented. The telechelic dithiols employed were prepared from nonconjugated dienes and a commercially available dithiol, or by esterification of adipic acid with 2-mercaptoethanol. From these dithiols, the diols were selectively obtained in high yields. Such α, ω-dihydroxylated compounds were characterized by both 1H and 13C NMR spectroscopy. The diol which exhibits the ester functions shows excellent solubility in common organic solvents contrarily to the other ones. The physical properties (Tg, Tm and decomposition temperatures) of these diols were compared and it is noted that the thermostability of these monodispersed telechelic diols is much better than those of the polydispersed commercially available ones such as poly(ethylene glycol)s or poly(tetramethylene glycol)s.
    Additional Material: 4 Ill.
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  • 9
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: (±), (+), and (-) poly[N-(sec-butyl)-N-methyl-acrylamides] (1) are obtained by radical polymerization of (±), (-), and (+) N-(sec-butyl)-N-methyl-acrylamides (AAM). By gradual hydrolysis in CH3COOH-HCl a series of copolymers was obtained (2); they are constituted by statistically distributed hydrophobic units derived from AAM and hydrophilic units derived from acrylic acid (AA) in different ratios as a function of the hydrolysis reaction time. Viscosity, optical rotation in methanol, solubility in various solvents, IR spectra from films and optical rotatory dispersion (ORD) have been studied as a function of the degree of conversion (τ). In order to explain the dependence of ORD and IR spectra on τ, the amid-acid hydrogen bonds were removed by methylation of COOH with diazomethane. During the neutralization of the different copolymers 2 by KOH, the increase in the ratio hydrophobic units/hydrophilic units strongly modifies the ionization behaviour of the COOH groups carried by the acrylic acid units.
    Notes: On hydrolyse progressivement en milieu acide (CH3COOH + HCl) les (±), (+) et (-) poly-[N-(sec-butyl)-N-méthylacrylamide] (1) obtenus par polymérisation radicalaire des (±), (-) et (+) N-(sec-butyl)-N-méthylacrylamides (AAM). On obtient une série de copolymeères (2) consititués de motifs hydrophobes dérivés de AAM et de motifs hydrophiles dérivés de l'acide acrylique (AA) répartis statistiquement et en proportion variable selon le temps d'hydrolyse. La viscosité, le pouvoir rotatoire dans le méthanol, la solubilité dans divers solvants, les spectres IR à l'état solide et la dispersion de la rotation optique (ORD) sont étudiés en fonction du taux d'hydrolyse. Pour interpréter l'évolution de l'ORD et des spectres IR on a supprimé les interactions H entre groupes amide et acide par méthylation de ces derniers au diazométhane. Au cours de la neutralisation des différents copolymères 2 par KOH, on constate que l'augmentation de la proportion des parties hydrophobes par rapport aux parties hydrophiles modifie fortement l'ionisation des groupes COOH des motifs monomères dérivés de l'acide acrylique.
    Additional Material: 6 Ill.
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  • 10
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
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