The effects of high temperatures (29-123°C) on critical micelle concentrations in solutions of potassium n-octanoate in deuterium oxide: A nuclear magnetic resonance study

Abstract

Critical micelle concentrations have been determined for potassium n-octanoate in deuterium oxide over a wide temperature range, 29-123°C, from the concentration dependence of proton nmr spectral parameters (peak positions, and vicinal splitting values of the α-CH2 multiplet) and carbon-13 nmr chemical shifts. The c.m.c. varies from ca. 0.30 m at ca. 30°C to ca. 0.50 m at ca. 120°C and is at a minimum (0.30-0.35 m) in the temperature range ca. 30-50°C. 23Na+ spin-lattice relaxation times reveal that a co-counterion (Na+) different from that of the surfactant counterion (K+) reflects the micellization process. A second critical micelle concentration has been observed around 1.0 m at ca. 30°C.