Thermodynamics of micellization of alkylsulphinylalkanols

Abstract

The thermodynamics of micellization of a new series of non-ionic surface-active agents, the alkylsulphinylalkanols (RSO(CH₂)_nOH), has been examined. It has been shown that the behaviour of methylene groups in close proximity to the hydrophilic groups is very different from those further removed. Thus, additional methylene groups in the alkyl chain remote from the head group give a decrease in enthalpy which accounts alsmost entirely for the decrease in free energy, while additional methylene groups between the sulphoxide and hydroxyl groups give an increase in enthalpy which is compensated by an increase in entropy. It has been inferred that the large increase in entropy which occurs on micellization arises from the loss of ordered water as the sulphoxide groups undergo co-operative solvation.