title: Solubilization of octane in cationic surfactant-anionic polymer complexes: effect of polymer concentration and temperature.
abstract: Polymers may alter the ability of oppositely charged surfactant micelles to solubilize hydrophobic molecules depending on surfactant-polymer interactions. This study was conducted to investigate the effects of polymer concentration and temperature on the solubilization thermodynamics of an octane oil-in-water emulsion in mixtures of an anionic polymer (carboxymethyl cellulose) and cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles using isothermal titration calorimetry (ITC). Results showed that the CTAB binding capacity of carboxymethyl cellulose increased with increasing temperature from 301 to 323 K, and correspondingly the thermodynamic behavior of octane solubilization in CTAB micelles, either in the absence or presence of polymer, was found to depend on temperature. The addition of carboxymethyl cellulose caused the solubilization in CTAB micelles to be less endothermic, and increased the solubilization capacity. Based on the phase separation model, the solubilization was suggested to be mainly driven by enthalpy gains. Results suggest that increasing concentrations of the anionic polymer gave rise to a larger Gibbs energy decrease and a larger unfavorable entropy increase for octane solubilization in cationic surfactant micelles.
authors.affiliation: College of Biosystems Engineering and Food Science, Fuli Institute of Food Science, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang R&D Center for Food Technology and Equipment, Zhejiang University, Hangzhou 310058, China; Department of Food Physics and Meat Science, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 21/25, 70599 Stuttgart, Germany.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: College of Biosystems Engineering and Food Science, Fuli Institute of Food Science, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang R&D Center for Food Technology and Equipment, Zhejiang University, Hangzhou 310058, China.
authors.forename: Lingli
authors.initials: L
authors.lastname: Deng
authors.affiliation: Department of Food Physics and Meat Science, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 21/25, 70599 Stuttgart, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Zeeb
authors.affiliation: Department of Food Physics and Meat Science, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 21/25, 70599 Stuttgart, Germany. Electronic address: j.weiss@uni-hohenheim.de.
authors.forename: Jochen
authors.initials: J
authors.lastname: Weiss
keywords: Isothermal titration calorimetry; Solubilization; Surfactant micelles; Surfactant–polymer complexes