Hemimicelle formation of semi-fluorocarbon chains at air–water interface: coarse-grained molecular dynamics study with an extension of the SPICA force field

Abstract

The hemimicelle formation of long-chain semi-fluorocarbon diblocks at the air – water interface is studied using coarse-grained molecular dynamics simulations with a SPICA force field. From a series of simulations with varying the number of chains, the critical saturated size of a single micelle was predicted; its structural metrics such as the hexagonal chain packing order, density distribution, shape, mean diameter, and the orientation of the fluorinated (F-blocks) and hydrogenated segments (H-blocks) at the interface were found to be consistent with the previous experimental and atomistic simulation results. The diblock assemblies larger than the saturated size spontaneously split into multiple micelles separated by a metastable parallel phase (P-phase). This P-phase could be the reason for the non-coalescence and elastic behaviour of the hemimicelle assemblies. From the simulation with a low molecular arrangement area, the mechanism of the micelle formation of saturated sizes is illustrated. The results reveal that the mutual-phobicity and interfacial tension difference of F- and H-blocks with the water are sufficient to drive the self-assembly and can provide a significant thermodynamic stability to the micelles, where the increasing packing strain between the layer curvature and the planarizing water surface tension can determine the size of the saturated hemimicelles.

GRAPHICAL ABSTRACT

KEYWORDS:

• Semi-fluorocarbon diblocks
• coarse-grained MD simulation
• hemimicelle
• P-phase
• air–water interface

Acknowledgements

This work was supported by AGC inc. For this study, the computational facilities of the supercomputer centre at Nagoya University; the Research Center for Computational Science, Okazaki; and the Institute for Solid State Physics, the University of Tokyo were used.

Disclosure statement

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

Additional information

Funding

This work was supported by AGC inc. For this study, the computational facilities of the supercomputer centre at Nagoya University; the Research Center for Computational Science, Okazaki; and the Institute for Solid State Physics, the University of Tokyo were used.