Interplay between surfactant self-assembly and adsorption at hydrophobic surfaces: insights from dissipative particle dynamics

ABSTRACT

We study the self-organisation of aqueous surfactants in bulk phase, and the adsorption and self-organisation of the aqueous surfactants at a planar hydrophobic surface by dissipative particle dynamics. Nonionic surfactants, n-alkyl poly(ethylene oxide) C${}_n$E${}_m$, and water are coarse-grained into mesoscopic beads comprising 1–3 heavy atoms and two water molecules, respectively. The size of the mesoscopic beads is related to the molar volume of the underlying molecular fragments while the bead–bead interaction parameters are calibrated against the water-octanol partition coefficients. We focus on the C${}_6$E${}_3$, C${}_6$E${}_4$, C${}_8$E${}_3$, and C${}_8$E${}_4$ surfactants in water that form spherical micelles in the bulk. The bulk micellization is primarily affected by the alkyl tail length which is demonstrated by an order of magnitude decrease in the critical micelle concentration when going from the aqueous C${}_6$E${}_m$ to aqueous C${}_8$E${}_m$ solutions. Surfactants strongly adsorb on the hydrophobic surface, adopting lying-down configurations and forming hemispheres which are in equilibrium with the spherical micelles in the bulk. In contrast to the bulk phase, the surfactant adsorption behaviour is influenced by both the alkyl tail and head chain lengths.

GRAPHICAL ABSTRACT

Keywords:

• Critical micelle concentration
• generic mesoscopic force field
• hemispheres
• mesoscopic beads
• nonionic surfactants

Acknowledgments

This work has received funding from the European Union's Horizon 2020 research and innovation program, project ‘VIMMP: Virtual Materials Marketplace’ (760907), and from the ERDF/ESF project ‘UniQSurf-Centre of Biointerfaces and Hybrid Functional Materials’ (CZ.02.1.01/0.0/0.0/17_048/0007411). This work was also supported by the Ministry of Education, Youth and Sports from the Large Infrastructures for Research, Experimental Development and Innovations project ‘IT4Innovations National Supercomputing Center’ (LM2015070). The access to computing and storage facilities owned by parties and projects contributing to the National Grid Infrastructure MetaCentrum provided under the program ‘Projects of Large Research, Development, and Innovations Infrastructures’ (CESNET LM2015042) is greatly appreciated.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work has received funding from the European Union's Horizon 2020 research and innovation program, project ‘VIMMP: Virtual Materials Marketplace’ [grant number 760907], and from the ERDF/ESF project ‘UniQSurf-Centre of Biointerfaces and Hybrid Functional Materials’ (CZ.02.1.01/0.0/0.0/17_048/0007411). This work was also supported by the Ministry of Education, Youth and Sports from the Large Infrastructures for Research, Experimental Development and Innovations project ‘IT4Innovations National Supercomputing Center’ [grant number LM2015070]. The access to computing and storage facilities owned by parties and projects contributing to the National Grid Infrastructure MetaCentrum provided under the program ‘Projects of Large Research, Development, and Innovations Infrastructures’ (CESNET LM2015042) is greatly appreciated.