MolecularDynamics Simulations of Structure–PropertyRelationships of Tween 80 Surfactants in Water and at Interfaces.

We build a united atom model forTween 80 (polyoxyethylene sorbitanoleates), based on the GROMOS53A6OXY+Dforce field, andapply it to two stereoisomers, three constitutional isomers, and threestructures with one, two, and three tails, to represent componentsin the Tween 80 commercial mixture. In a preassembled micelle containing60 molecules, the distribution of Tween tail and ethylene oxide headgroups is found to be insensitive to stereoisomerization but sensitiveto changes in relative lengths of the four polyoxyethylene head groups.At the air–water and oil–water interfaces, the interfacialtension is significantly lower for the constitutional isomer witha shorter W headgroup, which attaches the tail to the sorbitan ring,and for Tween 80 isomers with more than one tail group. The resultsindicate the possible scope for improvement in the design of polyoxyethylenesorbitan oleates with improved surface tension reduction or betterspreading at the oil–water interface. We also report surfactantcomponent distribution profiles within preassembled micelles and atinterfaces that can be used for validating coarse-grained surfactantmodels needed for simulation of self-assembly of Tween 80 surfactantmixtures. [ABSTRACT FROM AUTHOR]