jp034868y_si_001.pdf (226.15 kB)
Mass Action Model Applied to the Thermodynamic Properties of Transfer of Nonionic Copolymers from Water to the Aqueous Surfactant Solutions
journal contribution
posted on 2004-01-29, 00:00 authored by R. De Lisi, G. Lazzara, S. Milioto, N. MuratoreA thermodynamic model which enables the properties of aqueous copolymer/surfactant mixtures to be fit
quantitatively was proposed. Namely, a relationship between the properties of transfer of the unassociated
copolymer from water to the aqueous surfactant solutions (ΔYt) and the surfactant concentration was derived.
The model was based on the idea that ΔYt can be expressed in terms of the following contributions: (1)
interaction between monomers of copolymer and surfactant, (2) displacement of the monomer-micelle
equilibrium induced by the copolymer, (3) formation of the surfactant-copolymer aggregation complex, and
(4) formation of the mixed micelles. Such a model was applied to most literature data relative to the systems
formed by (ethylene oxide)13−(propylene oxide)30−(ethylene oxide)13 (L64) or (ethylene oxide)75−(propylene
oxide)30−(ethylene oxide)75 (F68) copolymers and hydrogenated surfactants, i.e., sodium octanoate, sodium
decanoate (NaDec), N-octylpyridinium chloride, and N,N-dimethyloctylamine-N-oxide. New enthalpy data
of both L64 and F68 in decyltrimethylammonium bromide were analyzed, as well. The appropriate comparison
among the parameters generated by the fitting processes gave physical insights on the mechanisms of binding
between the copolymer and the surfactant according to the quantitative model. The quantities obtained from
the minimizing procedure were used to predict ΔYt of the L64/NaDec system in conditions not yet investigated.
The agreement between the calculated values and the new experimental points was satisfactory.