Effect of temperature on the micellar properties of polyoxyethylene glycol ethers and twin tail alkylammonium surfactants

The pyrene fluorescence (I1II3) and conductivity (K) measurements of polyoxyethylene glycols ethers, such as C10E8, C12E4, C14E8, and alkylammonium cationic surfactants consisting of twin hydrophobic tails, such as 12-0-12, 12-2-12, and 14-2-14 have been carried out at different temperatures in the range of 283-313 K. The critical micelle concentration (cmc) of C10E8 shows a small decrease with an increase in temperature, while that of rest of the surfactants has relatively much less dependence on the temperature variation. The aggregation number of C10E8 and all the cationic surfactants slightly increases with an increase in the temperature. The excimer formation evaluated in the micellar solution of all these surfactants increases with an increase in temperature as well as increase in the hydrophobicities of both categories of surfactants. The evaluation of thermodynamic parameters reveals that greater spontaneity is achieved upon an increase in temperature as well as hydrophobicity. The micelles of non-ionic surfactants are more hydrophobic than those of cationic surfactants of comparable hydrophobicities despite the presence of twin hydrophobic tails in the category of surfactants. (c) 2005 Elsevier B.V. All rights reserved.