(346h) Evaluating Atomical Level Interfacial Structures of Multifunctional Energy Minimizing Surfaces Using Molecular Dynamics Simulations

Monolayer films are well recognized as a tool to design surfaces with tuned surface interactions (e.g. water- or oil-repellent surfaces) through modification of the film chemistry[1]. Such films have also been used to design films that are tunably responsive to external media, such as different solvents or pH[2,3]. However, these films are typically prohibitively slow in their responsiveness. In this work we aim to design surfaces that are immediately and reversibly switchable in response to a change in solvent through molecular dynamics simulations. Atomistic amorphous silica surfaces have been functionalized with short alkylsilane chains terminated with functional groups that are composed of competing hydrophobic and hydrophilic subgroups using the MoSDeF design framework[4]. Such terminal groups can achieve a dynamic switching response through molecular reorientation of the individual hydrophobic/hydrophilic groups in response to switching from a hydrophilic to a hydrophobic solvent. The relative size of these groups are varied and the difference in film structure is studied under water and n-hexane. It is shown that the interface is responsive to the nature of the solvent, and the degree of switchability is strongly affected by the length of the terminal group. Parameters are evaluated as quantifiable metrics for switchability which provide information about how the terminal group orients to define the solid liquid interface. These novel parameters will act as an objective function for understanding the types of responsive switching that can occur within the vast parameter space of these films.

References

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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. McCabe, “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.