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Soft Matter and Biological Physics


Eur. Phys. J. E 4, 489-504

Small-angle X-ray diffraction study of the thermotropic and lyotropic phases of five alkyl cyclic and acyclic disaccharides: Influence of the linkage between the hydrophilic and hydrophobic moieties

X. Auvray1, C. Petipas1, C. Dupuy1, S. Louvet1, R. Anthore1, I. Rico-Lattes2 and A. Lattes2

1  UMR CNRS 6634, Faculté des Sciences et des Techniques L.E.F.G.S., 76821 Mont Saint Aignan Cédex, France
2  Laboratoire des IMRCP, UMR CNRS 5623, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cédex, France

xavier.auvray@univ-rouen.fr

(Received 31 March 2000)

Abstract
We present a comparative study of the thermotropic and lyotropic phases of 5 surfactants with an aliphatic chain of 12 carbon atoms and a cyclic or acyclic sugar head with different linkages between the two moieties. These linkages can concern different chemical groups or different orientations between the head and the chain. The compounds included the $\alpha$- and $\beta$-N dodecyl-D-maltosides, N-dodecylamino-1-deoxylactitol, N-dodecyl lactobionamide and N-acetyl N-dodecyl lactosylamine. The influence of the polar head (with closed- and opened-type sugars) and the linkage with the hydrocarbon chain on the phases obtained by the heating of the anhydrous compounds and after addition of water was studied by X-ray diffraction and optical microscopy. In the anhydrous state, the surfactants were either crystalline or amorphous. On heating, they went through a liquid crystal smectic phase which, in some cases, was preceded by solid-to-solid transitions. On addition of water, the sequence of phases from the micellar phase to the lamellar phase was accounted for in terms of the geometric model of Sadoc and Charvolin. However, with certain surfactants this sequence was not complete, and the domains of existence of phases were altered.

PACS
61.30.Eb - Experimental determination of smactic, nematic, cholesteric and other structures.
61.10.Nz - Single crystal and powder diffraction.
64.70.Md - Transitions in liquid crystals.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001