Barman, S and Vasudevan, S (2007) Mixed saturated-unsaturated alkyl-chain assemblies: Solid solutions of zinc stearate and zinc oleate. In: Journal of Physical Chemistry B, 111 (19). 5212 -5217.
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The linear saturated stearic acid and the bent mono-unsaturated oleic acid do not mix and form solid solutions. However, the zinc salts of these acids can. From X-ray diffraction and DSC measurements we show that the layered zinc stearate and zinc oleate salts form a homogeneous solid solution at all composition ratios. The solid solutions exhibit a single melting endotherm, with the melting temperature varying linearly with composition but with the enthalpy change showing a minimum. By monitoring features in the infrared spectra that are characteristic of the global conformation of the hydrocarbon chain, and hence can distinguish between stearate and oleate chains, it is shown that solid solution formation is realized by the introduction of gauche defects in a fraction of the stearate chains that are then no longer linear. This fraction increases with oleate concentration. It has also been possible from the spectroscopic measurements to establish a quantitative relation between molecular conformational order and the thermodynamic enthalpy of melting of the solid solutions.
|Item Type:||Journal Article|
|Additional Information:||Copyright of article belongs to American Chemical Society.|
|Department/Centre:||Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Division of Chemical Sciences > Inorganic & Physical Chemistry
|Date Deposited:||10 Jun 2010 09:34|
|Last Modified:||19 Sep 2010 05:59|
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