Nonionic surface-active agents. Part V. The effect of the alkyl and the polyglycol chain length on the critical micelle concentration of some monoalkyl polyethers

Abstract

Critical micelle concentrations for a number of pure alkyl polyglycol surface-active agents of general formula CnH2n+1O·CH2·CH2)mOH (where n = 10, 12, or 16 and m = 4 to 9) have been measured by the surfacetension and the iodine methods. The values are affected by the alkyl and polyglycol chain lengths in the manner expected, except for the compounds in the hexadecyl series. The following equations, which have a similar form to those found for ionic surface-active agents, describe the results for the various series studied. For m = 6, log Cm = −0.5n + 1.03; n = 10, log Cm = 0.08m − 3.37; n = 16, log Cm = − 0.15m − 3.09, where Cm is the critical micelle concentration. Results for the dodecyl series agree closely with those reported by Lange (6). It seems possible that the anomalous results for the C16 glycols are due to the prolonged aging effects observed for these compounds. Although there is qualitative agreement with previous results which have been reported for nonionic glycols prepared by condensation reactions, good correlation is found only with results which have been given for alkyl glycols prepared by similar synthetic methods (6,7).