Effect of urea, guanidinium chloride, and dioxane on the c.m.c. of branched-chain nonionic detergents

The effect of urea on the c.m.c. of polyoxyethylene straight-chain alkanols has been reported in a previous investigation. The observed increments in c.m.c. values have been attributed to increased hydration of the ethylene oxide chain caused by a reduction of the cooperative structure of water. On the basis of analogous results obtained in this investigation with polyoxyethylene branched-chain nonylphenols, the possibility of channel compound formation in these highly concentrated urea solutions has been excluded. Comparable increments in c.m.c. values have also been observed with guanidinium chloride and dioxane at lower concentration levels than with urea. The former presents additional evidence for attributing these changes to increased hydration of the ethylene oxide chain caused by a reduction of the cooperative structure of water.