Abstract
The alkyl glucopyranosides are known to form smectic-like phases which are thermotropic in that they are obtained by heating without solvent. However, these substances are surfactants, and we show that the smectic phase is continuous with and thus identical to the ‘lyotropic lamellar’ phase exhibited by an Aerosol OT—water mixture. We also show that the smectic phase persists even in the presence of 20 wt. % water. The significance of these findings with regard to traditional definitions of thermotropic and lyotropic phases is discussed.