title: Solubilization of octane in cationic surfactant-anionic polymer complexes: Effect of ionic strength.
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 effect of ionic strength 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 indicated that the CTAB binding capacity of carboxymethyl cellulose increased with increasing NaCl concentrations up to 100 mM, and the thermodynamic behavior of octane solubilization in CTAB micelles, either in the absence or presence of polymer, was found to have a strong dependence on ionic strength. The increasing ionic strength caused the solubilization in CTAB micelles to be less endothermic or even exothermic, but increased the solubilization capacity. Based on the phase separation model, the solubilization was suggested to be driven by enthalpy. It is indicated that increasing ionic strength gave rise to a larger Gibbs energy decrease but a smaller unfavorable entropy increase for octane solubilization in cationic surfactant micelles.
authors.affiliation: Zhejiang University, 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, Hangzhou 310058, China; Department of Food Physics and Meat Science, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 21/25, Stuttgart 70599, Germany.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Zhejiang University, 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, Hangzhou 310058, China.
authors.forename: Lingli
authors.initials: L
authors.lastname: Deng
authors.affiliation: Ningbo Entry-Exit Inspection and Quarantine Bureau, Ningbo 315012, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Sun
authors.affiliation: Department of Applied Engineering, Zhejiang Economic and Trade Polytechnic, Hangzhou 310018, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Que
authors.affiliation: Department of Food Physics and Meat Science, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 21/25, Stuttgart 70599, 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