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  • 1990-1994  (1,169)
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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 169-184 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(vinyllactams) form a class of non-ionic water-soluble polymers from which only poly-(1-vinyl-2-pyrrolidone) (PVP) is well known and has been investigated extensively. The homologues poly(1-vinyl-2-piperidone) (1, poly[1-(2-oxo-1-piperidyl)ethylene]) and poly(N-vinylcaprolactam) (2, poly[1-(2-oxoperhydroazepin-1-yl)ethylene]) which are still soluble in water at room temperature have not yet been studied in aqueous solution. In this work the synthesis of these two polymers by radical polymerization in solution and the investigation of the dilute aqueous solution properties of these polymers by static and dynamic light scattering measurements are presented. Special attention is paid to the influence of the increasing hydrophobicity of these polymers on coil dimensions and structures in aqueous solution.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 155-167 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Six dicarboxylic acids (1a-f) were prepared from trimellitic anhydride and 4,4′-oxydianiline, 4,4′-methylenedianiline, 4,4′-sulfonyldianiline, benzidine, 1,6-hexamethylenediamine, and 4,4′-methylenedicyclohexylamine. These diacids were condensed directly with various aromatic diamines using triphenyl phosphite in 1-methyl-2-pyrrolidone/pyridine solution in the presence of calcium chloride. The inherent viscosity of the polymers is affected by the nature of the diamine and the solubility of the resulting polymers in the reaction media. The highest ηinh-value of a poly(amide-imide) obtained was 1,41 dl/g (in N,N-dimethylacetamide/5% LiCl at 30°C). Among the polymers, the wholly aromatic ones show better solubility, higher glass transition temperatures, and higher thermostability than the aliphatic-aromatic ones. Well-defined melting points (Tm) of most wholly aromatic poly(amide-imide)s were not obtained by differential scanning calorimetry (DSC); however, some poly(amide-imide)s containing aliphatic chains showed clear Tm in the first DSC heating traces. Measurements of wide-angle X-ray diffraction revealed that those polymers containing biphenyl or linear hexamethylene groups are partially crystalline. Flexible films with excellent tensile properties were cast from N,N-dimethylacetamide solutions of most of the wholly aromatic poly(amide-imide)s.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 185-198 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Blends of crystallizable poly(vinyl alcohol) (PVA) and poly-(N-vinyl-2-pyrrolidone) (PVP) of different molecular weights were prepared from aqueous solutions by evaporation and studied by Fourier-transform IR spectroscopy. When the molecular weight of one of the polymer components increases, the PVP content at which crystallinity in PVA is no longer observed decreases. The wide band representing hydroxyl stretching splits into four components at welldefined frequencies which are assigned to (1) multiple hydroxyl-hydroxyl bonding in organized PVA regions, (2) hydroxyls which are simply bonded to carboxyl, (3) hydroxyls doubly bonded to two carbonyls or to one carbonyl and one hydroxyl, and (4) simple hydrogen-hydrogen bonding in amorphous PVA regions. When the PVP content increases, the relative intensity of the bond of di-hydrogen-bonded hydroxyls remains quasi-invariant, while that of multiple hydrogen bonds in PVA decreases, and that of simple hydroxyl-carbonyl bonds increases correspondingly. It appears that the higher the molecular weight, the more effective the hindrance of PVP crystallization. An explanation of the mechanism leading to the formation of different structures in the blends is proposed on the basis of these results. It stresses the importance of the role of chain dynamics in an entangled chain network, which greatly affects the kinetics of crystallization of PVA during the drying step.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 199-211 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the pyridine-initiated polymerisation of simple 1,3-oxathiolan-2,5-diones (3a-c) in nitrobenzene was studied at various temperatures. Results show that, although the substituents in 4-position have a marked effect on rate of polymerisation, the polymerisation of the three monomers studied is linked by a common mechanism. Thus, the pyridine, nucleophile attacks the carbonyl in 5-position and forms a charge transfer complex which decomposes to form a highly reactive α-thiolactone intermediate 8 together with carbon dioxide and pyridine. Chain addition continues by the direct attack on the thiolactone by the terminal-SH group of traces of parent acid. The reaction of each of the three monomers with pyridine was found to show first order kinetic dependence on both monomer and pyridine, although the initiator (i.e. pyridine) is not consumed. The resultant polymers (molecular weight typically around 20000) are highly crystalline and relatively insoluble in common organic solvents.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 213-224 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of methyl α-(S)-malate with N,N′-dicyclohexylcarbodiimide in the presence of amines under mild conditions was studied. It was established that in solvents with weak donor properties, N-acyl derivatives are preferentially formed instead of ester condensation products. An optically active polymer fraction was separated by precipitation in diethyl ether (yield up to 30%) with M̄n,GPC 1 000 to 4 000 and of low polydispersity M̄w/M̄n = 1,1-1,4. The method permits the preparation of optically active biodegradable condensation products with controlled molecular structure.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 251-267 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The results of studies of co-metathesis reactions of 1,5-cyclooctadiene (1) with dimethyl 3-hexenedioate (2a) and for comparison, with 4-octene (2b) and 1,5-hexadiene (2c) are analyzed in order to approximate the relative reactivities of the carbene species and of the different types of double bonds. To this end, the experimental distributions of the first telomers are compared with theoretical ones calculated on the one hand allowing equal probability of arrangement of alkylidene groups and on the other hand allowing a kinetic control of propagation and transfer reactions. In other respects, the possibilities of mass control of the products obtained by the same co-metathesis or by degradation of 1,4-polybutadiene are studied. The results show that the reactivity of the 1,5-cyclooctadiene double bonds is higher than that of the other types of double bonds, this being in agreement with the hypothesis of stabilization of the β-carbomethoxycarbene species by carbene/ester complexation. This stabilization allows us to explain the distribution of α,β-difunctional oligomers in agreement with the hypothesis of kinetic control. The distribution of non-functional oligomers agrees with a random combination of alkylidene groups. This stabilization is compatible with the controlling method of molecular weights in the products obtained by polymerization of cyclooctadiene and also by degradation of 1,4-polybutadiene in the presence of 2a.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 269-279 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of the temperature of the melt T1 on the kinetics and the morphology of a semicrystalline polymer (poly(oxymethylene)) was investigated using thermal analysis and optical microscopy. The thermodynamic melting point Tf0 and the enthalpy of melting at thermodynamical equilibrium ΔHf0 were determined by extrapolation of the graphs Tf = f(Tc) and ΔHf = f(Tc); (Tf0 = 198°C, ΔHf0 = 251 J/g). For different temperatures of the melt (T1 = 185°C, 195°C, 205°C), isothermal and non-isothermal crystallizations were analysed using the Avrami and Ozawa equations. Nucleation and spherulitic growth in this polymer were studied by using optical microscopy at elevated temperatures. Using different analyses, we observed initial nucleation followed by spherulite growth with the following influence of the temperature of the melt on the distribution and the number of spherulites: T1 〈 Tf0 produces many small spherulites; T1 〉 Tf0 gives rise to few large spherulites.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 289-300 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Monte Carlo calculations for a modification reaction of 1,4-polybutadiene were carried out. The simulated process consisted in the substitution in α-position to the double bond, partially coupled with double-bond shift. The reaction model included mono- and disubstitution (one or two substituents at a carbon atom) and the formation of substituted double bonds in shift reactions. The number of molecules, the degree of polymerization and the degree of substitution were varied. The resulting multicomponent copolymers were evaluated with respect to different units (considered from one double bond to the next) and to their mole fractions. For example, more than 800 different units resulted for a mean of two substituents per unit. Units with up to 10 carbon atoms of the chain were found. Small molecule collectives gave representative results if only units above a minimum mole fraction were considered. The constitution of the products depended on the molecular size in the oligomer range. The distribution of the length of the units and of the number of substituents in a unit were determined.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 281-287 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular species proposed for the initial steps in the cationic polymerization of alkenylfurans were modeled by MNDO theoretically fully optimized structures. It was confirmed that the anomalous reactivity of ring C-5 of the monomers is determined by HOMO electron densitites, whereas calculated proton affinities from the semiempirical heats of formation fail to explain the low temperature experimental behavior of 2-vinylfuran (1c) from the point of view of stability of intermediate species. However, ab initio 4-31G calculations of proton affinities agree with the experimental facts and allow further explanations of the reactivity of furan derivatives in electrophilic media.
    Additional Material: 3 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 301-311 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel segmented multiblock copolymers (7) were synthesized by linking poly(ethylene oxide) (PEO) blocks with poly(β-benzyl L-aspartate)(PBLA) blocks via urethane and urea bonds, which were formed by the reaction of 4,4′-methylenediphenyl isocyanate (5) with the terminal hydroxyl groups of α-hydro-ω-hydroxypoly(oxyethylene) (4) and the terminal amino groups of poly(β-benzyl L-aspartate)-block-iminohexamethyleneimino-block-poly(β-benzyl L-aspartate) (3) [prepared from 1,6-hexanediamine (1) and β-benzyl L-aspartate N-carboxy anhydride (2)], respectively. Membranes with various water contents were obtained from these copolymers by changing the lengths of the PEO and PBLA segments. The study of the permeation of 1-phenyl-1,2-ethanediol, vitamin B12 and myoglobin through the membranes showed a high dependency of the permeability on the molecular weight of the solutes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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