Alkanediyl-α,ω-bis(dimethylalkylammonium bromide) surfactants (dimeric surfactants) Part 6. CMC of the ethanediyl-1,2-bis(dimethylalkylammonium bromide) series

Abstract

Recently, Dam et al. (Colloids and Surfaces A 118 (1996) 41) reported that dynamic surface tension did not permit them to observe the CMC of two dimeric surfactants, one of them being ethanediyl-1,2-bis(dimethyltetradecylammonium bromide) (14-2-14). We report that the CMC of this surfactant and of its longer chain homologue 16-2-16 show as a sharp break in the plots of the pyrene fluorescence intensity ratio I 1 I 3 and of the conductance versus 14-2-14 concentration. The CMC had previously been detected for the shorter homologues 12-2-12 and 8-3-8. The plot of log CMC versus carbon number is very close to linear, indicating very little premicellar association for the 16-2-16 surfactant, contrary to other series of dimeric surfactants with different spacers.