Phase behaviour of quaternary systems containing carbohydrate surfactants-water-oil-cosurfactant

Carbohydrate surfactants, such as n-alkyl beta-D-glucopyranosides (C(M)G(1) ) or 1-desoxy-1-N-methyldecanamido-D-sorbite (mega 10), are nearly insolubl e in n-alkanes and ternary mixtures of surfactant-water-n-alkane produce em ulsions. On adding a cosurfactant (butan-1-ol, octan-1-ol or phenol) the cl assical Winsor phase pattern, including middle-phase microemulsions, should appear. The experimental study of the formation and properties of microemu lsion states in multicomponent systems containing carbohydrate surfactant-w ater-oily component-cosurfactant is described with particular emphasis on p hase composition of co-existing phases with respect to comparable amounts o f water and oily component in one phase using HPLC analysis and the microst ructure of the microemulsion states applying dynamic light scattering and f reeze fracture electron microscopy. The phase behaviour as a function of th e cosurfactant concentration was investigated for different systems, varyin g the kind of cosurfactant, the tail length of the surfactant, the chemical nature of the polar head group and the polarity of the oily component. The experiments were carried out at constant temperature, at constant surfacta nt concentration in the feed phase and at constant water-to-oil ratio in th e feed phase. The most striking experimental observation is that adding a c osurfactant to a carbohydrate-water-oil mixture promotes the formation of m icroemulsion structures for all investigated systems, except for the system n-decyl beta-D-glucopyranoside (C(10)G(1))-water-n-octane-octan-1-ol. An i mportant property of microemulsions is the ability, under carefully chosen conditions, to incorporate very large amounts of oil and water into homogen eous solutions.