LETTER TO THE EDITOR
Lecithin Organogels with Alkylglucosides n -Octyl-b-D-glycopyranoside 1 of 99% purity was purchased from Alexis ( Switzerland ) . n -Decyl and n -dodecyl derivatives of b-D-glyco-Oscillation rheology was used to study the viscoelastic properties pyranoside were synthesized according to the method developed in ( 7 ) . of lecithin organogels with included aand b-anomers of alkylglun -Decyl-a-D-glycopyranoside was prepared as in ( 8 ) . It contains about cosides as well as their derivatives containing an alkyl chain of 2.5% of b-DGP. various length. The alkylglucosides caused an equal decrease of n-Decane was of puriss quality from Fluka. Water was purified by double zero shear viscosity. Pronounced difference was established in their distillation. effects on the plateau modulus. Derivatives with a shorter alkyl
The jelly-like phases were made by dissolution of weighed appropriate chain brought about an increase in the plateau modulus, whereas amounts of lecithin, alkylglycosides, and water into n-decane. The method derivatives with a longer chain decreased it. FTIR spectroscopic was detailed in (4, 5). measurements showed that there is a distinction in the alkylgluco-
The viscoelastic properties of lecithin organogels in the frequency range side effect on hydrogen bonds formed by the lecithin phosphate 0.001 to 10 Hz were characterized by making use of a Bohlin CS-10 stress- controlled rheometer supplied with a cell with cone-and-plate geometry.
group. It was suggested that the changes observed in the molecular
This is described more fully in (9). The experiments were performed at interactions within micelles are responsible for the variation of the 25.0 { 0.1ΠC.
rheological parameters through the relaxation time for the micellar
Absorbance IR spectra were obtained by means of a Mattson FTIR specbreaking/recombination. α§ 1998 Academic Press trometer (Polaris). A minimal resolution was 0.5 cm 01 . The thickness of Key Words: lecithin; alkylglucosides; polymer-like micelles; orthe specimen compartment of a cell completed with NaCl windows was ganogel; hydrogen bonds; viscoelasticity; plateau modulus; dyequal to 0.25 mm. namic rheology.
RESULTS AND DISCUSSION
The frequency dependencies of the storage modulus G, loss modulus GΠ, and complex viscosity Γh*Γ measured for lecithin organogels are not