Tricritical points and wetting - Nonwetting transitions in nonionic microemulsions

Proceeding in a homologous series of oils and nonionic amphiphiles, we stud y the dependence of the coordinates of tricritical points and wetting --> n onwetting transitions on the carbon number of the oils, and the strength of the amphiphiles. We find an inverse relation in that weakly nonpolar oils require strong amphiphiles for to be emulsified, whereas for emulsifying st rongly nonpolar oils, weak amphiphiles suffice. The results are discussed q ualitatively on the basis of a simple model inspired by Harkins.