2025 AIChE Annual Meeting

(336d) Molecular Simulation of Patterned Interfaces: Linking Dewetting to Adsorption Thermodynamics

Authors

Camille Bilodeau - Presenter, University of Virginia
Md Jakir Hossen, University of Virginia
Adel Nematipour, University of Virginia
Molecular-scale hydrophobicity plays a key role in many important interfacial phenomena ranging from adsorptive separations1,2 and fouling3,4 to colloidal assembly5,6 and protein aggregation7. While macroscopic hydrophobicity can be experimentally measured using a simple contact angle, hydrophobicity at molecular length-scales is difficult to quantify and depends on surface chemistry and patterning in unintuitive ways4,8–12.

In this work, we investigate the relationship between surface pattern and hydrophobicity focusing on two specific questions: 1) how does hydrophilic group spacing impact surface hydrophobicity and 2) how does hydrophilic group chemistry (i.e. number of hydrogen bond donor/acceptors, geometry, net charge, etc.) impact surface hydrophobicity? We address these two questions by studying a series of model patterned surfaces at a variety of hydrophilic group spacings and chemistries. To measure the “hydrophobicity” of the surface, we compare and contrast two different views of hydrophobicity. First, we apply Indirect Umbrella Sampling (INDUS) an enhanced sampling technique that enables the direct measurement of the free energy of cavity formation. Second, we perform spatial umbrella sampling to obtain a free energy of binding of two model hydrophobic solutes, Hydrophobin and a gold nanoparticle functionalized with an alkyl thiol SAM. We show how our definition of hydrophobicity is sensitive to the exact parameters used for INDUS calculations and establish a theoretical framework for connecting the energetics calculated using INDUS to the free energy of binding of hydrophobic solutes. Finally, using a methodology that is both connected to solute adsorption, but also not specific to the solute chemistry, we explore how hydrophilic group spacing and chemistry impact surface hydrophobicity. This work lays a foundation for connecting dewetting calculations to adsorption as well as for understanding how surface chemistry and patterning govern surface hydrophobicity.

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