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  • Digitale Medien  (5)
  • 1960-1964  (2)
  • 1950-1954  (3)
  • 1930-1934
  • Chemistry  (5)
Materialart
  • Digitale Medien  (5)
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  • 1
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 10 (1953), S. 19-28 
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The various stages employed in the production of a phenolformaldehyde cast resin are discussed. It is assumed that the chains formed during the condensation stage undergo a rearrangement upon acidification to yield roughly spherical, stabilized micelles. These micelles are concentrated by dehydration until coalescence begins. At this point the chains again rearrange and the resin becomes the continuous phase. Pronounced changes in the properties of the system are observed at this critical point. The effects produced by undercondensation, overcondensation, overdehydration, etc. are mentioned briefly. The ionizable components, by determining the interfacial pH during the curing stage, are shown to be directly related to the rate of cure, stability, color, light transmissibility, etc. of the cured casting. Transparent castings are expected only when an ionizable component of the proper refractive powers is oriented at the interface. An examination of the immediately available data provides a lead to the future changes that can be expected as aging progresses.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 14 (1954), S. 315-319 
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 0022-3832
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 330 (1964), S. 295-308 
    ISSN: 0044-2313
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: pK′ values of carbethoxyalkylphosphines, carbamidoalkylphosphines and carboxy-alkylphosphines of the general formula R2P—R′—COR″ (R″ = —OC2H5, —NH2, and —OH, respectively) are determined potentiometrically using water - ethanol or water as the solvent.The basicity of the P atom in these compounds depends on the kind of R (alkyl, cycloalkyl or aryl group) and R′ (linear or branched alkylene group) and is influenced by the position of the COOC2H5, CONH2 and COOH group, respectively.IR and NMR spectra of the carboxyalkylphosphines indicate no dipolar structure of these P-analogous amino acids.
    Notizen: In Fortsetzung einer früheren Arbeit(2) werden durch potentiometrische Titration in Äthanol-Wasser bzw. Wasser die pK′-Werte der Carbäthoxyalkylphosphine R2P—R′—COOC2H5, der Carbamidoalklphosphine R2P—[CH2]n—CONH2 und der Carboxyalkylphosphine R2P—R′—COOH bestimmt.Die Basizität des P-Atoms dieser Verbindungen der allgemeinen Formel R2P—R′—COR″ wird durch die Art der Gruppen R und R′ beeinflußt (R = Alkyl-, Cycloalkyl- oder Arylgruppe; R′ = lineare oder verzweigte Alkylengruppe) und hängt von der Stellung der COR″-Gruppe ab.Aus IR- und NMR-Spektren folgt, daß die den Aminosäuren im Formeltyp entsprechenden Carboxyalkylphosphine weder in fester Form noch in THF-Lösung eine dipolare Struktur besitzen.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 5
    ISSN: 0449-2951
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: When, in a poly-α-olefin, the probability that a given placement be isotactic depends upon the tacticity of only a finite number of immediate predecessors, the resulting diastereosequence distribution obeys the theory of Markoff chains. When this is not the case, one says that the resulting diastereosequence distribution is non-Markoffian. A special case of a Markoffian distribution is given by a simple Markoff chain in which the tacticity of a given placement is assumed to be affected by only the tacticity of the immediately preceding placement. Another special case is, of course, the Bernoulli trial distribution in which the probability that a given placement be isotactic is independent of the tacticity of all other placements. A high resolution NMR spectrum can sometimes yield a quantitative determination of the concentrations of isotactic and syndiotactic placements and the concentrations of the three types of possible adjacent pairs of such placements (i.e., isotactic, syndiotactic, and heterotactic pairs). When this is the case, the spectrum can be used to determine whether or not a given diastereosequence distribution is Bernoullian. However, because the longest diastereosequences whose concentration can be measured by NMR spectroscopy involve only two placements, an NMR spectrum cannot check whether a given non-Bernoullian distribution be simple Markoffian or Markoffian in general. In fact, non-Markoffian distributions are compatible with existing NMR spectra on polymers prepared by anionic polymerizations. In this paper we work within the framework of Kac's theory of stationary statistical processes and point out some general results which are valid for both Markoffian and non-Markoffian processes. The results are applied to NMR spectroscopy and it is pointed out which calculations used to check the self-consistency of NMR data and to obtain the mean length of closed diastereosequences are valid for both Markoffian and non-Markoffian distributions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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