Kinetic and equilibrium studies associated with the aggregation of non-ionic surfactants in non-polar solvents

The aggregation properties of poly(oxyethylene)alkyl ether, non-ionic surfactants (CnEOm), have been studied in the non-polar solvents heptane and decane using light scattering, vapour pressure osmometry and ultrasonic relaxation methods. The results show that the degree of association is low and only small aggregates (N≈ 5–15) are present. The aggregation numbers increase with EO size, and are slightly larger in decane than in heptane. Alkyl chain size has no influence on aggregation. Only at high concentrations does the association phenomenon resemble the behaviour expected from micellar solutions.