Dynamic Molecular Switching for Environmentally Adaptive Surfaces

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While surfaces generally have fixed compositions, the ability to design dynamic surfaces that rapidly alter their composition when the environment is changed can impact several areas, including prevention of surface contamination and facilitation of adsorption/desorption. This project will combine experiments and molecular simulations to design and characterize molecular films that rapidly change their surface composition when the external environment is altered. This change in composition will be accomplished by molecular surface groups that display both “hydrophobic” and “hydrophilic” components. The hydrophobic components will orient to dominate the surface when exposed to air or a nonpolar solvent, whereas the hydrophilic components will orient to occupy the surface when exposed to water. The investigators will use these films to study new self-cleaning and thermoresponsive surfaces. Outreach for this project includes offering a one-week intensive course on nanotechnology to gifted middle school students and a molecular modeling cybercamp. Discoveries from this research will provide fertile design examples for the elective courses taught by the investigators, who are both award-winning teachers. The investigators will continue to be strong mentors for undergraduate and graduate students, including those from underrepresented backgrounds, to propel students toward careers in science and engineering. This collaborative project will combine experiments and molecular simulations to design and develop a class of molecular films that are instantaneously adaptive to their environment. These films will become energetically minimized when exposed to a new environment through the orientation of multifunctional surface groups. In the first objective, molecular simulations and experiments will be combined to design, synthesize, and assemble a class of molecular adsorbates for preparation of environmentally adaptive monolayer films. Computational screening using the Molecular Simulation Design Framework (MoSDeF) will allow for rapid screening of the identified parameter space; promising adsorbates will then be experimentally synthesized and assembled. In the second objective, the most promising films will be thoroughly investigated to maximize the magnitude of the response, establish the mechanism of the interfacial switching, and further optimize the molecular design. In the third objective, the developed design tools will be used to construct pH- and thermo-responsive surfaces and self-cleaning amphibious surfaces that can minimize adventitious contamination, shed oil, and resist biofouling. Since the environmental adaptation described here is simply a reorientation of a surface group, these systems would offer immediate response to minimize interfacial free energy upon exposure to a new environment, unlike commonly studied materials that rely on macromolecular motion and are restricted to specific solvents or environments. The proposed materials and surfaces will be designed based on a tight collaboration between molecular simulations and experiments for targeted adaptation around known environmental cues, such as continual transitions between liquid and air, solvent and water, different pH values, or temperature.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.