Dowanol DPnB in water as an example of a solvo-surfactant system: Adsorption and foam properties

Abstract

Dowanols being chem. ethers of n-alkanols with bis(isopropylene glycol) represent characteristic properties of hydrotropic mols. or solvosurfactants, i.e. they have some surfactant properties in addn. to typical solvent properties. The dynamic surface tension behavior of aq. Dowanol solns. (c ≤ 10-1 M) is a consequence of different surface-active components owing to the presence of different isomers and surface-active contaminants. By applying a special purifn. method (flounder technique) the authors removed addnl. (non-Dowanol) surface-active trace impurities by aspirating them from the highly compressed adsorption layers. The various sucked off fractions reveal peculiar surface properties that are quite different from those of the original and of the surface-chem. pure solns. Whereas the former show only short-time foam stability of a few seconds, the sucked-off fractions formed (meta)stabile foams lasting for a few hours. The Dowanol's solvo-surfactant characteristic is caused by the synergistic effect of various surface-active species rather than by the special structure of an individual component