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  • 1
    Electronic Resource
    Electronic Resource
    Comparative characterization of MgCl2/ethyl benzoate/TiCl4 and MgCl2/2,2,6,6 tetramethylpiperidine/TiCl4 Ziegler-Natta precatalysts (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1137-1147 
    Details
    ISSN: 0887-624X
    Keywords: Ziegler-Natta catalysts ; propylene polymerization ; catalysts characterization ; supported catalysts ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article we present the results of the preparation and characterization of two Ziegler-Natta precatalysts: MgCl2/Ethyl benzoate (EB)/TiCl4 and MgCl2/2,2,6,6 tetramethylpiperidine (TMPiP)/TiCl4 by means of FTIR, X-ray diffraction, SEM, BET surface area measurements, and other techniques applied at different steps of their preparation procedures.The precatalysts were prepared by impregnating with TiCl4 a given amount of MgCl2, which was previously ball-milled with the electron donor chosen.Prior to impregnation, the ball-milled material presented different surface compounds depending on the electron donor used: [(MgCl2)2] · 2EB, MgCl2 · EB, or a salt of the amine. The solid milled with EB is more homogeneous than the one milled with the TMPiP.Titanium is better retained in the solid milled with EB. This precatalyst has better morphological properties and larger BET surface area. By means of FTIR, we found evidences that an adequate surface structure for the formation of stereospecific sites in MgCl2/TMPiP/TiCl4 was formed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080320616
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  • 2
    Electronic Resource
    Electronic Resource
    Stereochemistry and dynamic behavior of some synthetic “angular” profisetinidin tetraflavanoid derivatives (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 835-849 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure and stereochemistry of four synthetic “angular” tetraflavanoid-condensed tannin derivatives are examined by high-resolution variable temperature 1H NMR. spectroscopy, and hence correlated with their dynamic behavior. Three “angular” oligomers exist as stable rotational isomers at ambient temperatures, thus contrasting with the mobility about their interflavanoid bonds of most natural profisetinidin “trimeric” and “tetrameric” homologs. A “linear” tetraflavanoid analog results from one of these regioselectively controlled condensations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080240503
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  • 3
    Electronic Resource
    Electronic Resource
    A conjugated polymer-based voltage-regulator deviceThe authors thank CNPq. CAPES. PADCT, and FAPERGS for financial support. (1997)
    Weinheim : Wiley-Blackwell
    Advanced Materials 9 (1997), S. 972-974 
    Details
    ISSN: 0935-9648
    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
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19970091209
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  • 4
    Electronic Resource
    Electronic Resource
    The kinetics and mechanism of polyethylene photo-oxidationPaper presented at the “15th Annual International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 2-4, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 216 (1994), S. 113-133 
    Details
    ISSN: 0003-3146
    Keywords: polyethylene ; photo-oxidation ; weathering ; mechanism ; kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the natural and accelerated photo-oxidation of low-denisty polyethylene (LDPE) films have been studied; different geographical locations have been selected for the natural tests, and a range of temperatures used in the accelerated experiments in a specially built temperature-controlled ultraviolet radiation enclosure. A meaningful correlation between natural and accelerated weathering results was established, by means of an adequate superposition of the effects of UV radiation exposure and temperature. Reasonably detailed and accurate, lumped-parameter, kinetic models of the photo-oxidation process have also been developed, to interpret and predict the results of measurements of carbonyl, hydroperoxide and vinyl absorbances as functions of time and temperature; the models predict the general experimental behaviour, and also that both the formation of hydroperoxides and carbonyl Norrish-I reactions are important initiation steps. More complex models have the potential of interpreting other fine details of the degradation behaviour, namely the generation of other chemical species, and the chain scission and cross-linking process which are directly related to changes in the mechanical properties.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052160108
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  • 5
    Electronic Resource
    Electronic Resource
    Permeation of organic vapors through polymer in the condensation region (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 727-734 
    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: Permeability coefficients have been measured for normal butane, isobutane, isobutylene, and butene-1 in Zendel Copolymer-I at temperatures between 30° and 70°C and at penetrant pressures p1 up to 5.5 atm. The permeability coefficients of these organic vapors show behavior analogous to that observed for C3 and C2 hydrocarbons as detailed in our earlier work; i.e., near the condensation point of the penetrant, P increases as the temperature is decreased. Isothermal plots of log P versus p1 in that region are generally linear and can be represented by empirical relations of the form \documentclass{article}\pagestyle{empty}\begin{document}$$ P = P_0 \exp \left( {ap_1 } \right) $$\end{document} where P0 is a constant. The slope a is a function of temperature: \documentclass{article}\pagestyle{empty}\begin{document}$$ a = a_0 \exp \left( {bt} \right) $$\end{document} where a0 is a constant and b has the same value for the four hydrocarbons investigated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1974.070180310
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  • 6
    Electronic Resource
    Electronic Resource
    Condensates of phenol, resorcinol, phloroglucinol, and pyrogallol as model compounds of flavonoid A- and B-rings with formaldehyde (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 24 (1979), S. 1571-1578 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070240618
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  • 7
    Electronic Resource
    Electronic Resource
    Surface layers on fe formed during plasma nitriding studied by XPS and reflection EELS (1988)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 12 (1988), S. 211-217 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Anomalous compound surface layer growth is observed during plasma nitriding of ferrous materials under certain operating conditions. The formation of an iron oxy-nitride layer by the redeposition of sputtered cathode material was found to influence the growth kinetics of the γ'-Fe4N layer which forms during plasma nitriding of α-Fe to the extent where the γ'-Fe4N surface layer initially increases and subsequently decreases in thickness after deposition of the iron oxy-nitride layer. The nature of these layers was studied by XPS and reflection EELS to elucidate the electron structure of the valence bands of these compunds. Results are Results are presented which explain the thermodynamic stability of the iron oxy-nitride layer and the apparent de-nitriding effect that this layer formation has on the underlying γ'-Fe4N layer.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740120307
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  • 8
    Electronic Resource
    Electronic Resource
    Electropolymerization of pyrrole on Fe and Pt electrodes in methanol and acetonitrile. Evidence of interfacial layers resulting from accumulation and decomposition of the supporting electrolyte (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 749-754 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The partial decomposition of PF6- during pyrrole electropolymerization in methanol and acetonitrile on Fe and Pt electrodes is demonstrated using XPS analysis. A complex mixture of PF6-, fluorides of phosphorus and metal oxides is shown to exist in the interfacial region, probably resulting in a weak cohesive layer unfavourable to the adhesion of polymer films.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740200902
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  • 9
    Electronic Resource
    Electronic Resource
    Spectroscopic properties of free phenolic 4-arylflavan-3-ols as models for natural condensed tannins (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 1057-1063 
    Details
    ISSN: 0749-1581
    Keywords: 4-Arylflavan-3-ols ; 1H NMR ; 13C NMR ; Circular dichroism ; Condensed tannins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A unique range of free phenolic 4-arylflavan-3-ols consisting of four sets (3′,4′,5,7-tetrahydroxyflavan-3-ol or its 5-deoxy analogue coupled to phloroglucinol or resorcinol), each composed of three diastereomers (2,3-trans-3,4-trans, 2,3-trans-3,4-cis and 2,3-cis-3,4-trans) were synthesized to assess their spectroscopic properties. 1H and 13C NMR and circular dichroism data are related to selected structural and stereochemical features with a view to modelling natural phenolic oligoflavanoids.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260311206
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  • 10
    Electronic Resource
    Electronic Resource
    Conformational analysis of oligomeric flavanoids. 2For Part 1, see Ref. 8. - methyl ether acetate derivatives of profisetinidins (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 611-620 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; condensed tannins ; profisetinidins ; stereochemistry ; conformation ; rotational isomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The profisetinidins are the most important polyflavanoids of commerce, making up the major constituents of wattle and quebracho tannins. Even within the dimeric profisetinidins, substantial complexity exists because of stereo-, regio-, rotational and conformational isomers. Definition of the stereochemistry of the upper and lower flavan units, the location of the interflavanoid bond, the conformation of the heterocyclic rings in the upper and lower flavan units and the conformations of major and minor rotational isomers in a series of methyl ether acetate derivatives of dimeric profisetinidin diastereomers is possible by application of COSY and NOE experiments. All compounds studied were present in two rotameric forms with the more compact conformation favored. The heterocyclic ring in the upper chain extender unit was predominantly in an E-conformation (i.e. half-chair in 2R,3S isomers and a ‘reverse’ half-chair in the 2S,3R isomers). The heterocyclic ring conformation of the terminal cate-chin unit, although mostly in an E-conformation, was often represented by significant proportions of A-conformers.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330802
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