Abstract:

The hydration behavior of the system polyoxyethylene (10) oleyl alc. [C18:1(EO)10 or Brij 97]/water/dodecane/butanol (model system B) was investigated along a diln. line for which the resp. wt. ratio of dodecane:butanol:Brij 97 is 3:3:4. Two exptl. methods were applied: time domain dielec. spectroscopy (TDDS) and sub-zero temp. differential scanning calorimetry (SZT-DSC). Two types of bound water (with melting peaks at - 25 and - 11°C) were detected by SZT-DSC (using the endothermic mode), whereas TDDS revealed only one such type. Nevertheless, roughly the same total amt. of bound water was estd. from these two techniques. The av. no. of bound water mols. per ethylene oxide (EO) group, NW/EO, is 2.3 (TDDS data) or 2.5 (SZT-DSC data) in good agreement with the observation that 1-2 water layers are formed in the hydration of ethoxylated surfactants. We have also shown that butanol is involved in the formation of the bound water that melts at - 25°C. We suggest that butanol mols. occupy binding sites within the second hydration shell, thereby reducing the expected total bound water content. [on SciFinder(R)]