Conductometric study of sodium dodecyl sulfate-nonionic surfactant (Triton X-100, Tween 20, Tween 60, Tween 80 or Tween 85) mixed micelles in aqueous solution

The present study is concerned with the determination of the critical micelle concentration (cmc) of mixed micelles of sodium dodecyl sulfate with one of five nonionic surfactants (Triton X-100, Tween 20, Tween 60, Tween 80 or Tween 85) from conductance measurements. Based on the calculated values of the beta parameter we have noticed that SDS-nonionic surfactants mostly showed strong synergistic effects. It was found that nonionic surfactants with mainly longer and more hydrophobic tails show stronger interactions with hydrophobic parts of SOS, thus expressing stronger synergism. The strongest synergistic effect was noticed in an SDS-Tween 80 binary system. The SDS-Tween 85 micellar system showed antagonistic effect, most probably because the presence of the double bond in its three hydrophobic tails (three C18 tails) makes it sterically rigid.