Phase behaviour of alkyl polyglucosides in combination with fatty alcohols and alkyl sulphates

Abstract

Dilute C 12 14 alkyl polyglucoside (Glucopon600CS®) solutions containing small amounts of fatty alcohols (hydrocarbon chain length greater than 4) show three different lamellar phases (L αl, L α−h, L αh) which are characterized by increasing fatty alcohol: surfactant ratios. The middle lamellar phase appears, in some aspects, like a mixture of the lower and upper lamellar phases. The lower and middle lamellar phases are optically biaxial and are therefore probably in tilted crystalline states. The upper lamellar phase is in the liquid state and is uniaxial. On the addition of alkyl sulphates together with the appropriate amount of the fatty alcohols, to a 5% alkyl polyglucoside solution the middle lamellar phase predominates. Pentanol and hexanol favour the upper lamellar phase while longer-chain fatty alcohols favour the lower lamellar phase. A cholesteric phase with characteristic fingerprint texture appears in highly concentrated surfactant solutions containing decanol or higher fatty alcohols. The characteristic fingerprint texture of this phase is due to myelinic figures which occur in the two-phase region between the lower lamellar phase and an isotropic phase. The fingerprints can be oriented in strong magnetic fields. The cholesteric phase interacts strongly with polarized light which is travelling in the direction of the helical axis.