| Autor: |
Anderson RL; STFC Hartree Centre, Scitech Daresbury , Warrington WA4 4AD , United Kingdom., Bray DJ; STFC Hartree Centre, Scitech Daresbury , Warrington WA4 4AD , United Kingdom., Del Regno A; STFC Hartree Centre, Scitech Daresbury , Warrington WA4 4AD , United Kingdom., Seaton MA; STFC Hartree Centre, Scitech Daresbury , Warrington WA4 4AD , United Kingdom., Ferrante AS; Ferrante Scientific Ltd. , 5 Croft Lane , Bromborough CH62 2BX , United Kingdom., Warren PB; Unilever R&D Port Sunlight , Quarry Road East , Bebington CH63 3JW , United Kingdom. |
| Abstrakt: |
We use dissipative particle dynamics (DPD) to study micelle formation in alkyl sulfate surfactants, with alkyl chain lengths ranging from 6 to 12 carbon atoms. We extend our recent DPD force field [ J. Chem. Phys. 2017 , 147 , 094503 ] to include a charged sulfate chemical group and aqueous sodium ions. With this model, we achieve good agreement with the experimentally reported critical micelle concentrations (CMCs) and can match the trend in mean aggregation numbers versus alkyl chain length. We determine the CMC by fitting a charged pseudophase model to the dependence of the free surfactant on the total surfactant concentration above the CMC and compare it with a direct operational definition of the CMC as the point at which half of the surfactant is classed as micellar and half as monomers and submicellar aggregates. We find that the latter provides the best agreement with experimental results. Finally, with the same model, we are able to observe the sphere-to-rod morphological transition for sodium dodecyl sulfate (SDS) micelles and determine that it corresponds to SDS concentrations in the region of 300-500 mM. |
