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  • Chemistry  (108)
  • Analytical Chemistry and Spectroscopy  (17)
  • Biochemistry and Biotechnology  (17)
  • 2005-2009  (1)
  • 1990-1994  (81)
  • 1980-1984  (19)
  • 1975-1979  (7)
  • 1935-1939
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  • 1
    Electronic Resource
    Electronic Resource
    Photodegradation of polyethylene films formulated with a titanium-based photosensitizer and titanium dioxide pigment (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 847-856 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This work reports on the photodegradation of low-density polyethylene films formulated with titanium (IV) oxide actylacetonate (TAc) and titanium dioxide pigment in different proportions; no previous reports on the photoactivity of this acetylacotonate have been found. Samples of blow-extruded films were submitted to accelerated UV aging with fluorescent lamps and the polymer degradation measured. The changes in carbonyl groups, molecular weight, and film elongation at break are discussed. The results show that TAc can promote photooxidation and accelerate the film degradation. The retention percent of elongation at break (EB) is apparently proportional to the carbonyl index irrespective of the formulation but has different relations with molecular weight (Mn), time, or the number of chain scissions (n), probably as a result of microstructural differences. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530702
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  • 2
    Electronic Resource
    Electronic Resource
    Dextran functionalized by cyclic carbonate groups as supports of bioactive compounds (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 206 (1993), S. 77-85 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es werden Aspekte der Reaktion von Dextran mit Ethyl-chlorformiat und Triethylamin als Katalysator behandelt. Mittels 1H- und 13C NMR-Spektroskopie wurden in den gebildeten modifizierten Dextranen cyclische und acyclische Carbonatgruppen nachgewiesen. Vorversuche zeigten, daß die Reaktion cyclischer Carbonatgrupen mit verschiedenen Amin-Modellverbindungen stark vom Basencharakter des Amins abhängt. Phenethylamin und Tyramin wurden quantitativ an aktiviertes Dextran mit cyclischen Carbonatgruppen gebunden. Die Dextran-Phenethylamin- und Dextran-Tyramin-Addukte werden unter den angewendeten Bedingungen (pH 1,0 oder 9,1 bei 37°C) nicht heterogen hydrolysiert.
    Notes: This work deals with some features of the reaction of dextran with ethyl chloroformate using triethylamine as catalyst. The presence of cyclic and acyclic carbonate groups in the resulting modified dextrans was demonstrated by IR, 1H and 13C NMR spectroscopy. Preliminary experiments have shown that the reaction of cyclic carbonate groups with several model amines is greatly dependent on the basic character of the amine. Model amino type drugs (Phenethylamine and tyramine) were quantitatively bound to activated dextran with cyclic carbonate groups. The heterogeneous hydrolysis of dextran-phenethylamine or dextran-tyramine adducts showed that no hydrolysis takes place under the applied conditions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052060108
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  • 3
    Electronic Resource
    Electronic Resource
    Notizen. Sterisch gesteuerte Reaktionswege von substituierten 2-Norbornyl-Kationen (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 815-818 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Steric Control in the Reaction of Substituted 2-Norbornyl CationsThe reaction of camphenilone (1b) with trifluoromethanesulfonic anhydride (Tf2O) yields 7,7-dimethyl-1,exo-2-bis(trifluoromethylsulfonyloxy)norbornane (4b) (60%). 6,6-Dimethyl-2-norbornanone (1c) affords under the same conditions 6,6-dimethyl-2-norbornen-2-yl triflate (5c) (70%). The reaction pathways of the intermediate 2-(trifluoromethylsulfonyloxy)-2-norbornyl cations are mostly controlled by steric factors, the inductive effect playing no significant role.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160237
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of reprocessing on the mechanical properties of a commercial polysulfone/polycarbonate blend (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 861-867 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Commercial polysulfone/polycarbonate (PSU/PC) polymer blends were reprocessed up to five times to determine the influence that reprocessing has on their structure and physical properties. All the high strain properties, mainly ductility, significantly decreased under harsh processing conditions, such as five cycles at 320°C. The results of reprocessing the blends at 320°C have been compared with results at a lower temperature and also with those of the separate components with the aim of clarifying the origin of the degradation. These results plus Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis, and melt flow index measurements (MFI) indicate that the presence of the two polymers together clearly decreases the resistance to degradation of each component. Moreover, degradation under the stated conditions is mainly thermal and does not change the chemical nature of the blends. However, a clear decrease in molecular weight was observed both by viscosimetry and MFI measurements as was a shift to higher temperatures of the low temperature secondary transition of both PC and PSU. Both molecular weight and secondary transition changes usually deteriorate mechanical properties but not in the degree observed here. This probably means that the fine and difficult-to-observe structure of the blend has also changed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321305
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  • 5
    Electronic Resource
    Electronic Resource
    Synthèse et réactions photochimiques d'homopolymères et de copolymères de la p-vinylbenzophénone et du vinylferrocènePartie de la thèse soutenue par G. Sánchez devant l'Université Strasbourg I, Louis Pasteur. (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 131-146 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(p-vinylbenzophenone), (poly[1-(4-benzoylphenyl)ethylene]), (PVB) has been synthesized for the first time directly from its monomer p-vinylbenzophenone (VB) the preparation of which was improved. In a second step, copolymers containing blocks of photosensitive VB units separated by isolated quenching vinylferrocene (VF) units have been prepared. PVB and the VB-VF copolymers were irradiated in the presence of isopropyl alcohol in benzene solutions. The benzophenone groups inserted in these macromolecular chains obey the same reaction scheme as the photoreduction of the small molecule of benzophenone. However, recombination of the radicals located along the polymeric chain leads to intra- and intermolecular reactions changing drastically the macromolecular morphology by the formation of cycles and networks and by chain scissions. The quantum yields of the photochemical transformations were measured, but they could not be related quantitatively to morphological parameters. In all cases the ferrocene group inhibits strongly the photochemical reaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1978.021790113
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanical properties of chitosan films: Effect of solvent acid (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 1353-1359 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The apparent Young's modulus shows a linear relationship with junction density of chitosan films. The linear relationship of apparent Young's modulus with chitosan concentration is also observed. The linear relationship depends of the acid used in the casting solution. Relaxation times were of the order of 104 seconds, indicating a slow physical process. Stress-relaxation behavior of swollen chitosan films, prepared by solvent casting from dilute acetic or propionic acid solutions, can be represented by a one-component Maxwell model.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021830528
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  • 7
    Electronic Resource
    Electronic Resource
    Sequence distribution and glass transition of vinyl alcohol/n-alkyl vinyl carbonate copolymers (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 2153-2159 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 13C NMR spectroscopy was used for the determination of the sequence distribution in vinyl alcohol-ethyl vinyl carbonate copolymers prepared by reaction of poly(vinyl alcohol) with ethyl chloroformate. The 13C NMR spectra of the methylene carbons in the main chain show three split peaks whose intensities change with copolymer composition. These peaks can be assigned to the three dyad sequences. The obtained results show that ethyl vinyl carbonate units have an alternating tendency in the copolymer chain. The Tg values of the vinyl alcohol-ethyl vinyl carbonate and vinyl alcohol-butyl vinyl carbonate copolymers are influenced by both the overall copolymer composition and the monomer sequence distribution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021851010
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis and controlled release behaviour of esters from amylose and 1-naphthylacetyl chloride (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 1513-1518 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work deals with the modification reaction of amylose with 1-naphthylacetyl chloride using pyridine as catalyst and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by IR, 1H and 13C NMR spectroscopy. A linear dependence of the reaction rate on the concentration of polymer, 1-naphthylacetyl chloride and pyridine was found. The activation energy was found to be 32,4 kJ/mol. The hydrolysis in the heterogeneous phase showed that the release of the active compound from tablets is dependent on the hydrophilic character of the modified amylose as well as on the pH value of the medium.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910704
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  • 9
    Electronic Resource
    Electronic Resource
    Relation between structure and thermal transitions in comb-like polymers, 1. Poly(N-n-alkylmaleimide)sDedicated to Prof. Dr. D. C. Pepper, on the occasion of his 65th birthday (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 2643-2659 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of nine poly(N-n-alkylmaleimide)s (PMIs) with the n-alkyl side chain ranging in length from ethyl to octadecyl and including only the even members of the series was studied by differential scanning calorimetry (DSC) from 100 K to above the glass transition temperature. The nine members of the PMI series generally were found to exhibit a glass transition temperature (Tg), a sub-glass transition temperature (sub-Tg = Tγ), and, but only the four higher homologs a melting point (Tm) with the respective melting enthalpy (ΔHf). The glass transition of the amorphous members is directly related to the number of methylene groups (including terminal methyl) of the n-alkyl side chain of the repeating unit. The values of Tg estimated according to a semi-empirical equation are in good agreement with the experimental data. The melting points of the members of the series presenting crystallinity in the n-alkyl side chain were analyzed. A good fit of a Garner plot by a least-mean-squares procedure is obtained with T0m = 408,0K, a = -6,26 and b = -2,03. The contribution to the heat of melting per methylene unit clearly demonstrates that the hexagonal paraffin crystal structure is present in the crystalline members, in agreement with X-ray data. The data when analyzed by Jordan′s procedure show that only part of the n-alkyl side chain is forming a crystal lattice.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021841222
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  • 10
    Electronic Resource
    Electronic Resource
    Some fundamental studies of the reaction of poly(vinyl alcohol) with alkyl chlorophosphates (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1733-1739 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The modification reaction of poly(vinyl alcohol) with diethyl chlorophosphate and ethyl dichlorophosphate is studied in homogeneous phase using tertiary amines as catalysts. The structure of the modified polymers was determined by means of 1H and 31P{1H} nuclear magnetic resonance (NMR) spectroscopy as well as by chemical analysis. The structure of the polymers resulting from the reaction with diethyl chlorophosphate greatly depends on the reaction temperature as well as the catalyst. For lower reaction temperatures (≤25°C) only acyclic phosphate ester groups were observed. The activation energy was found to be 24,9 kJ/mol. The presence of cyclic phosphate ester groups was found, when higher reaction temperatures (〉25°C) were used. These results can be interpreted considering the existence of transesterification reactions. Crosslinking structures were obtained in case ethyl dichlorophosphate was used instead of diethyl chlorophosphate.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920807
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