(9i) Dynamic Molecular Switching for Environmentally Adaptive Surfaces

Monolayer films provide a coating through which surface interactions (e.g. water-and oil-repellent surfaces, lubricating films, biological implants, and adhesives) can be modified and tuned by changing the chemistry of the film.¹ Efforts have been made to design films that are responsive to changes in external medium;^2,3 however, such films are slow to respond or require external stimuli to change. Here we report molecular dynamics simulations of amorphous silica surfaces functionalized with short (6-18 carbons) alkylsilane chains terminated with functional groups that are composed of competing hydrophobic and hydrophilic subgroups. Such terminal groups can achieve a dynamic switching response through reorientation of the individual hydrophobic/hydrophilic subgroups which minimizes surface energy in response to contrasting environments. Changing the chemistry of the competing subgroups, chain surface density, chain length, and the presence of secondary chains (backfills) is examined to identify systems and conditions where dynamic switching occurs in response to changes in solvent. This vast parameter space is screened using the MoSDeF software suite⁴ with the Signac⁵ workflow manager.

References

[1] M. C. Stuart et al., “Emerging applications of stimuli-responsive polymer materials,” Nature Materials, 2010, 9: 101-113.

[2] S. M. Kang, I. You, W. K. Cho, H. K. Shon, T. G. Lee, I. S. Choi, J. M. Karp, H. Lee, “One-Step Modification of Superhydrophobic Surfaces by a Mussel-Inspired Polymer Coating” Int Ed Engl. 2010, 49(49): 9401–9404.

[3] Bo He and Junghoon Lee, "Dynamic wettability switching by surface roughness effect," The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003, MEMS-03, pp. 120-123.

[4] A. Z. Summers, J. Gilmer, C. Iacovella, P. Cummings, C. M^cCabe, “MoSDeF, a Python Framework Enabling Large-Scale Computational Screening of Soft Matter: Application to Chemistry-Property Relationships in Lubricating Monolayer Films,” JCTC., 2020, 16: 1779-1793.

[5] C. S. Adorf, P. M. Dodd, V. Ramasubramani, and S. C. Glotzer. “Simple data and workflow management with the signac framework”, Comput. Mater. Sci., 2018, 146(C):220-229.