n-Alkanol induced clouding of Brij® 56 and the energetics of the process

The clouding behavior of the nonionic surfactant polyoxyethylene (10) cetyl ether (Brij® 56) has been investigated in the presence of n-alkanols of varying chain lengths (C1–C10). It was observed that the short-chained, water soluble n-alkanols delayed the clouding behavior, while the more hydrophobic long-chained n-alkanols promoted the clouding behavior of the surfactant. A linear dependency of the cloud point variation on the n-alkanol concentration was also observed. The energetics of clouding were determined as a function of n-alkanol concentration and analyzed in terms of dehydration of the head groups and association of the dehydrated molecules leading to phase separation in the presence of these additives.