GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    X-ray diffraction studies on homologous thallium soaps below the temperature range of the neat phase 1. Calculation and comparison of the structure parameters of unit cells (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 267-281 
    Details
    ISSN: 1435-1536
    Keywords: Thalliumsoaps ; X-raydiffraction ; latticeparameters ; unitcell ; phasebehavior ; polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The results of X-ray diffraction patterns of homologous thallium soaps TlC n (n-8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 20 and 22) in dependence on the temperature showed that the structures of the phases below the temperature range of the liquid-crystalline neat phase (so called phase C1, phase C2, phase I, phase II) are crystalline-like, not liquid-crystalline. As function of the chain length of the fatty acid group, we found the following phase sequences to be a function of temperature: TlC8: phase I↔neat phase: TlC9−Tl14: phase C2↔phase II↔phase I↔neat phase; TlC15, TlC16: phase C1↔phase II↔phase I↔neat phase; TlC17−TlC22: phase C1↔phase II↔neat phase. From the X-ray patterns of the thallium soaps were calculated the lattice parameters and the unit cells of these homologues at various temperatures. The comparison between the lattice parameters of the homologues showed, surprisingly, that these parameters were independent of chain length and temperature. This X-ray data are the basis for the following development of structure models of the phase C1, phase C2, phase I, and phase II, including the neat phase (see Part 2).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655479
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    X-ray diffraction studies on homologous thallium soaps below the temperature range of the neat phase 2. Structure models of crystalline modifications in the temperature range below the neat phase (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 282-297 
    Details
    ISSN: 1435-1536
    Keywords: Thalliumsoaps ; polymorphism ; structuralmodels ; “herring-bone-like”crystallinemodifications ; neatphase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In Part 1 were discussed the results of X-ray diffraction measurements on homologous thallium soaps, the lattice parameters and the unit cells of the different phases: phase C1, phase C2, phase I, phase II, and the neat phase. The aim of Part 2 is the development of structural models, based on data on lattice parameters, packing densities of hydrocarbon chains and head groups. In order to supplement our experimental data we carried out infrared-spectroscopic measurements at different temperatures within the existence regions of these phases to get additional information on alterations in configurations of head groups and hydrocarbon chains of thallium soaps in these phase regions. By comparing the structural models we can generalize that the phase C1, phase C2, phase I, and phase II have some properties in common: they form crystalline structures, their unit cells are monoclinic, and the angles α and β are orthogonal. The amount of the lattice parametersc is equal to the distances of two molecular bilayers and/or twice the distance between the lamellae. Among the normal lamella, the molecules form a “herring-bone-like” packing. This indicates that the lamellar structure of the liquid-crystalline neat phase is already preformed in these crystalline modifications of phase C1, phase C2, phase I, and phase II. These crystalline phases differ in their lattice parameters and their packing coefficients. The transition from the crystalline phase I or phase II into the neat phase is accompanied by a temperature-dependent contraction of the distances between the lamellae, which originates in the “fluidity” of the hydrocarbon chains. Simultaneously, the lattice parametersa andb are drastically shortened and attain dimensions considerably lower than the values obtained in crystalline modifications. The X-ray scattering properties of the Tl+-ions suggest that the Tl+-ions exist in a “fluid-like” state within the head groups region of the neat phase. We came to the conclusion that the thallium-oxygen-bond is remarkably less polar than the bonds between alkali ions and oxygen resulting from the electro-negativity of the metal-oxygen-bonds of the alkali soaps, in comparison to the thallium soaps. Hence, the absence of polymorphic liquid-crystalline semiphases of thallium soaps is due to the low polarity of the thallium-oxygen-bond. Structure formation of Tl-soaps is mainly influenced by the hydrocarbon chain packing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655480
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...