Azeotropic mixing of C16peLac with different surfactants of monomeric and dimeric nature under the effect of temperature

The steady state fluorescence measurements have been performed for the binary mixtures of N-hexadecyl-N′-lactobionylethylenediamine (C16peLac) with a variety of surfactants such as 3-(N,N-dimethylhexadecylammonio) propane sulphonate (HPS), dodecylhexadecyldimethyl ammonium bromide (12-0-16), trimethylene-1,3-bis(dodecyldimethylammonium bromide) (12-3-12), and hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) over the whole mixing range in the temperature range of 15–45 °C. From the variation of I1/I3 intensity ratio of pyrene fluorescence, the critical micelle concentration (cmc) of single and mixed surfactants has been determined. The nature of the mixed micelles has been evaluated with the help of regular solution theory. The micellar parameters such as micelle mole fraction (X1), and regular solution interaction parameter (β), have been determined for all the binary mixtures. It has been observed that the mixed micelles of C16peLac + 12-0-16/HPS are formed due to synergistic interactions while unfavorable interactions have been found during the mixed micellization of C16peLac + 12-3-16/12-6-12 mixtures. The former behavior came from the reduction in the polar head group repulsions of 12-0-16 and HPS upon the intercalation of C16peLac. On the other hand, large spacer groups in bulky dimeric head groups as in case of 12-3-12 and 12-6-12 results in unfavorable interactions with C16peLac.