Tensiometric studies on the mixtures of nonionic Cremophor RH and cationic gemini surfactants.

Surfactant solutions used in practical applications are generally mixtures of ionic and nonionic surfactants. These surfactants mostly show synergism on mixing. In this work, mixing behavior of cationic gemini surfactants, alkanediyl — α, ω — bis(dimethylalkylammonium bromide (alkyl: 14 or 16 and alkane: butane, pentane or hexane)), (m-s-m) and Cremophor RH over the entire mole fraction range was investigated tensiometrically. Results indicate that these mixtures show a negative deviation in the cmc id (cmc value at ideal mixing conditions). Micellar mole fraction of RH (X 1 m ) values indicate that RH has slightly higher contribution in mixed micelles than of geminis. X 1 m values are greater than of X 1 σ (mole fraction of RH at mixed interface). Adjustment of cationic head group of gemini is easier at the planar interface than in curved micellar head group area. Surface excess increases with the increase in α 1 . Different thermodynamic parameters (i.e., ΔG° mic , ΔG° ads , ΔG ex m , ΔG ex σ , G min ) also support mixed micelle formation. R p value and radius of micelles suggest that the mixed micelles at high α 1 are almost cylindrical in shape. [ABSTRACT FROM AUTHOR]