ADSORPTION OF NORMAL-ALKYLTHIOOLIGOOXYPROPYLENE GLYCOLS AT AQUEOUS-SOLUTION AIR INTERFACE

Surface active n-alkylthiooligooxypropylene glycols C(n)H2n+1SCH2CH(CH3)- (OCH2CH (CH3))(z)OH n = 4, 6, 8; z = 0-5 where synthesized and equilibrium surface tension-concentration isotherms of aqueous solutions of these individual substances at 293 K were determined. A new empirical equation dealing with the adsorption process of a whole group of non-ionic surface active substances at the aqueous solution-air interface has been applied to the compounds studied. It has been found that the thiopropylene group, -SCH2CH(CH3)-, is hydrophobic. The standard free energy contribution, DELTA-G-pi-o [-SCH2CH(CH3)-], is not constant. The change in its value from -1.02 to -2.02 RT with the change in surface pressure-pi from 0 to 25 mM m-1 is discussed.