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Hydrocarbon chain conformation in an intercalated surfactant monolayer and bilayer

Venkataraman, NV and Vasudevan, S (2001) Hydrocarbon chain conformation in an intercalated surfactant monolayer and bilayer. In: Journal of Chemical Sciences, 113 (5&6). pp. 539-558.


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Cetyl trimethyl ammonium (CTA) ions have been confined within galleries of layered CdPS3 at two different grafting densities. Low grafting densities are obtained on direct intercalation of CTA ions into CdPS3 to give Cd0.93PS3(CTA)(0.14). Intercalation occurs with a lattice expansion of 4.8 Angstrom with the interlamellar surfactant ion lying flat forming a monolayer. Intercalation at higher grafting densities was effected by a two-step ion-exchange process to give Cd0.93PS3(CTA)(0.14), with a lattice expansion of 26.5 Angstrom. At higher grafting densities the interlamellar surfactant ions adopt a tilted bilayer structure. C-13 NMR and orientation-dependent IR vibrational spectroscopy on single crystals have been used to probe the conformation and orientation of the methylene tail of the intercalated surfactant in the two phases. In the monolayer phase, the confined methylene chain adopts an essentially all-trans conformation with most of the trans chain aligned parallel to the gallery walls. On lowering the temperature, molecular plane aligns parallel, so that the methylene chain lies flat, rigid and aligned to the confining surface. In the bilayer phase, most bonds in the methylene chain are in trans conformation. It is possible to identify specific conformational sequences containing a gauche bond, in the interior and termini of the intercalated methylene. These high energy conformers disappear on cooling leaving all fifteen methylene units of the intercalated cetyl trimethyl ammonium ion in trans conformational registry at 40 K.

Item Type: Journal Article
Publication: Journal of Chemical Sciences
Publisher: Indian Academy Sciences
Additional Information: Copyright for this article belongs to Indian Academy of Sciences.
Keywords: Intercalation;layered compound;surfactant assembly;conformation
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 22 Sep 2004
Last Modified: 19 Sep 2010 04:16
URI: http://eprints.iisc.ac.in/id/eprint/1986

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