Effect of polyvinylpyrrolidone on the self-assembly of model hydrocarbon amphiphiles

• Published in: Journal of colloid and interface science Vol. 137; no. 1; pp. 204 - 216
• Main Authors: Chari, Krishnan, Lenhart, William C
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.06.1990; Elsevier
• Subjects: Chemistry; Exact sciences and technology; Gas-liquid interface and liquid-liquid interface; General and physical chemistry; Surface physical chemistry; Molecular arrangement; Gas liquid interface; Micelle; NMR spectrometry; Experimental study; Free energy; Aggregation; Sodium Compounds; Anionic surfactant; Pyrrolidone(vinyl) polymer; Organic sulfate; Surface tension; Aqueous solution; Thermodynamic properties
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/0021-9797(90)90057-U

The arrangement of molecules in the polymer-surfactant complex and the standard free energy of formation of the complex in an aqueous solution of anionic surfactant and polyvinylpyrrolidone (PVP) are investigated using 13C NMR spectroscopy and surface tension measurement at the air/water interface. The behavior of the single-chained surfactant, sodium dodecyl sulfate (SDS), is compared with that of the double-chained surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol OT). It was found that the basic structure of the complex is the same in both cases; the surfactant molecules are assembled in a micelle-like aggregate; and the polymer molecules are wrapped around the aggregate, shielding hydrocarbon groups on the surface of the micelle from contact with water. For SDS the standard free energy of micellization is lowered by 1.5 RT per mol in the presence of PVP. However, for Aerosol OT the decrease in the free energy of micellization is only 0.7 RT per mol. The lesser influence of PVP on the monomer-micelle equilibrium in solutions of Aerosol OT is attributed to the presence of the highly polar carbonyl groups in the shell of the Aerosol OT micelle which are believed to act as a barrier to the attachment of the backbone of the polymer to the surface of the micelle.