Aqueous Solutions of Sodium Deoxycholate and Hydroxypropylmethylcellulose: Dynamic Surface Tension Measurements

• Published in: Journal of colloid and interface science 2000-01, Vol.221 (2), p.223-229
• Main Authors: Avranas, Antonis, Tasopoulos, Vasilis
• Format: Article
• Language: English
• Subjects: Applied sciences; Cellulose and derivatives; dynamic surface tension; Exact sciences and technology; hydroxypropylmethylcellulose; Natural polymers; Physicochemistry of polymers; sodium deoxycholate; Wilhelmy plate method
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.1999.6574

Interfacial tension changes and interaction between sodium deoxycholate (DOC) and a nonionic polymer hydroxypropylmethylcellulose (HPMC) were studied by the Wilhelmy plate method. The concentration of HPMC was fixed at 8×10−5, 2×10−4, and 1×10−3% (w/v) while DOC ranged form 0 to 8×10−2 M, i.e., concentrations below and above the critical micellar concentration (cmc) for DOC. Emphasis was placed on the highly diluted solutions of the polymer in order to lessen possible contributions of the effects of the bulk phase on the observed surface behavior. The dynamics of the surface tension was investigated in the presence and absence of DOC. The kinetics of the interfacial tension changes were explained in terms of adsorption of the polymer molecules and conformational changes of already adsorbed molecules at the interface. The molecules above a critical DOC aggregation concentration (cac) formed clusters, which was evidenced by these surface tension measurements. A synergism in surface activity was observed below that cac. The cmc of DOC remained unchanged by the presence of HPMC.