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Synergism in mixed monolayers of alkylpolyglucoside and alkylsorbitan surfactants at liquid/liquid interface
Author(s) -
Cinteza Otilia,
Dudau Manuela
Publication year - 2003
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-003-0270-5
Subject(s) - pulmonary surfactant , chemistry , surface tension , monolayer , partition coefficient , phase (matter) , phase diagram , chromatography , thermodynamics , chemical engineering , organic chemistry , engineering , biochemistry , physics
A study of nonideal behavior in the formation of mixed monolayers at the oil‐water interface was performed for a nonionic‐nonionic surfactant system. Mixtures containing alkylpolyglucoside and alkylsorbitan derivatives were investigated. As the oily phase, colza‐rapeseed and olive oils were used. To evidence a synergetic effect in the interfacial tension reduction in the oil‐water‐surfactant‐cosurfactant system, the model based on the regular solution theory was modified for the case of both surfactants being soluble in the water as well as in the oily phase. For determination of the condition for the synergism and the point of the maximum synergetic effect, the molar fraction in the mixed monolayer X s and the interaction parameter β s were calculated, using experimental data for the interfacial tension and for the partition coefficient. A set of general equations was developed, to allow the analysis of a mixture containing a water‐soluble and an oil‐soluble surfactant. The equations are applied according the characteristics of studied quaternary systems. The mathematical model was tested with literature data, and the results were compared with those obtained from the phase diagram of oil‐water‐mixed surfactant system. The systems water‐vegetable oil‐alkylpolyglucoside‐alkylsorbitan show a maximum synergetic effect at molar fractions between 0.85 and 0.90. The liquid‐liquid interfacial tension and partition coefficient data were used to calculate the point of the maximum synergetic effect, i.e., the surfactant‐cosurfactant ratio, which ensures the interfacial tension miniumum. The dramatic reduction in interfacial tension due to the presence of the surfactant mixture at the interface at the point of the synergism maximum is related to the formation of three‐phase and single‐phase microemulsions. The results were applied to obtain single‐phase microemulsion in water‐vegetable oil‐alkylpolyglucoside‐alkylsorbitan systems.