Structure and aggregation proclivity of C12E3 in aqueous solution

Abstract

Olygo(ethylene glycol) alkyl ethers – CxEy are well known for their high surface activity and rich phase behavior. These substances exhibit some unusual aggregation characteristics in aqueous solution even at concentrations well below CMC attributed to the formation of pre-aggregates of small size, e.g., dimers. To verify this, a series of C12E3 dimers with initial geometries taken from coarse-grained molecular dynamics simulations is subject to geometry optimization with two quantum chemical methods: DFT and ONIOM in implicit water solvent. The resulting structures are classified into groups based on structural parameters. Their stability is assessed by relative and binding energy and rationalized in terms of molecular characteristics.All studied dimers are stable and various mutual alignments of the surfactants therein are feasible. The loss of surface area is outlined as the predominant stabilizing factor. Substantial number of the structures is suitable for further aggregation.