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Phase and Rheological Behavior of Cetyldimethylbenzylammonium Salicylate (CDBAS) and Water
Author(s) -
CarvajalRamos Francisco,
GonzálezÁlvarez Alejandro,
Roger VegaAcosta J.,
ValdezPérez Donato,
Fernández Escamilla Víctor Vladimir Amilcar,
Macías Balleza Emma Rebeca,
Félix Armando Soltero Martínez J.
Publication year - 2011
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/s11743-010-1223-6
Subject(s) - chemistry , rheometry , differential scanning calorimetry , phase (matter) , analytical chemistry (journal) , rheology , lamellar structure , phase diagram , dynamic mechanical analysis , pulmonary surfactant , atmospheric temperature range , thermodynamics , chromatography , crystallography , organic chemistry , polymer , biochemistry , physics
The temperature–composition phase diagram in the diluted region of the cationic surfactant cetyldimethylbenzylammonium salicylate/water system was studied with a battery of techniques. The Krafft temperature ( T k = 33 ± 1 °C) was measured by differential scanning calorimetry, polarizing microscopy, conductimetry, viscosimetry, and rheometry. The critical vesicle concentration (cvc, ∼0.002 wt%) and a vesicle–micellar transition (cvm, ∼0.005 wt%) was detected at a temperature of 35 °C. Below T k and concentrations ≤2 wt%, a transparent solution is formed (I). Above 2–8.5 wt%, a lamellar (L 1 ) phase forms. At higher concentrations and up to 12 wt%, a second lamellar phase (L 2 ) is detected. From 12.4 to 15.5 wt%, an emulsion phase (E) is formed. Rheological dynamic measurements for the I phase indicate that the system exhibits a predominantly viscous behavior ( G ′ < G ″) for concentrations lower than the overlap or entanglement concentration ( C e , ∼0.75 wt%). At higher concentrations, wormlike micelles form and the elastic behavior predominates ( G ′ > G ″). The elastic ( G ′) modulus collapses in a concentration–time master curve in the whole reduced frequencies range ωτ c examined, whereas the viscous modulus ( G ″) collapses only at reduced frequencies lower than 0.1. Reduced stress plotted as a function of the reduced shear rate yields a good superposition of the curves at the different concentrations up to the onset of the non‐linear behavior.