je7b00880_si_001.pdf (770.84 kB)
Micellisation of Binary Mixtures of Surfactants Na-Deoxycholate–Na-Decyl Sulfate and Na-Hyodeoxycholate–Na-Decyl Sulfate in Water Solutions: Rational Development of the Thermodynamic Model for the Excess Gibbs Energy (GE)
journal contribution
posted on 2018-02-08, 18:34 authored by Mihalj Poša, Ana Pilipović, Vesna Tepavčević, Stoja ObradovićMicellisation of two binary mixtures,
sodium decyl sulfate (NaDS)–sodium
deoxycholate (NaDC) and sodium decyl sulfate (NaDS)–sodium
hyodeoxychlolate (NaHDC), is examined, in consideration with the different
molar fractions of the monomers (x = 0.1–0.9).
In bile acids, the OH groups attached to steroid skeletons are spatially
ecraned, while the sulfate group of NaDS is not ecraned. Thus, NaDC
and NaHDC in relation to NaDS have different coordination numbers
in the micelle pseudophase. On the basis of stereochemical analysis,
rational design shows that the excess Gibbs energy (GE) of formation of the binary mixed micelle throughout
the whole composition range can be described with a two-parameter
Margules function, while the GE function
from the regular solution theories is applicable only in the narrow
interval of the bile salts molar fractions (x = 0.5–
0.8). Coefficient of activity (hypothetical) of the infinitely diluted
mixed micelle of NaDS in the presence of NaDC shows significant thermodynamic
stabilization of decyl sulfate ions in comparison with the infinitely
diluted hypothetical mixed micelle with NaHDC. This stabilization
of decyl sulfate ions is probably due to the cooperative binding of
NaDS by parallel OH groups of NaDC.