Evidence for the intrusion of polyoxyethylene into the hydrocarbon core of non-ionic surfactant micelles

The intrinsic viscosities, [eta], of non-ionic surfactants of structure, CH3[CH2]m-1[OCH2OCH2]1.25mOH, were measured in water at 298 K. [eta] increased linearly with hydrocarbon chain length from m = 3 to m = 15, and between m = 17 and m = 31. There was a discontinuity between m = 15 and m = 17, which was attributed to intrusion of some polyoxyethylene into part of the hydrocarbon core for surfactants in which m greater than 15. This effect gave a micellar hydration which was lower than expected for the higher members of the series. Other factors relevant to the intrusion of polyoxyethylene into hydrocarbon are discussed.