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Affinity of small-molecule solutes to hydrophobic, hydrophilic, and chemically patterned interfaces in aqueous solution.
Monroe, Jacob I; Jiao, Sally; Davis, R Justin; Robinson Brown, Dennis; Katz, Lynn E; Shell, M Scott.
Affiliation
  • Monroe JI; Department of Chemical Engineering, University of California, Santa Barbara, CA 93106.
  • Jiao S; Department of Chemical Engineering, University of California, Santa Barbara, CA 93106.
  • Davis RJ; Department of Civil, Architectural and Environmental Engineering, University of Texas at Austin, Austin, TX 78712.
  • Robinson Brown D; Department of Chemical Engineering, University of California, Santa Barbara, CA 93106.
  • Katz LE; Department of Civil, Architectural and Environmental Engineering, University of Texas at Austin, Austin, TX 78712.
  • Shell MS; Department of Chemical Engineering, University of California, Santa Barbara, CA 93106; shell@engineering.ucsb.edu.
Proc Natl Acad Sci U S A ; 118(1)2021 01 05.
Article in En | MEDLINE | ID: mdl-33372161
ABSTRACT
Performance of membranes for water purification is highly influenced by the interactions of solvated species with membrane surfaces, including surface adsorption of solutes upon fouling. Current efforts toward fouling-resistant membranes often pursue surface hydrophilization, frequently motivated by macroscopic measures of hydrophilicity, because hydrophobicity is thought to increase solute-surface affinity. While this heuristic has driven diverse membrane functionalization strategies, here we build on advances in the theory of hydrophobicity to critically examine the relevance of macroscopic characterizations of solute-surface affinity. Specifically, we use molecular simulations to quantify the affinities to model hydroxyl- and methyl-functionalized surfaces of small, chemically diverse, charge-neutral solutes represented in produced water. We show that surface affinities correlate poorly with two conventional measures of solute hydrophobicity, gas-phase water solubility and oil-water partitioning. Moreover, we find that all solutes show attraction to the hydrophobic surface and most to the hydrophilic one, in contrast to macroscopically based hydrophobicity heuristics. We explain these results by decomposing affinities into direct solute interaction energies (which dominate on hydroxyl surfaces) and water restructuring penalties (which dominate on methyl surfaces). Finally, we use an inverse design algorithm to show how heterogeneous surfaces, with multiple functional groups, can be patterned to manipulate solute affinity and selectivity. These findings, importantly based on a range of solute and surface chemistries, illustrate that conventional macroscopic hydrophobicity metrics can fail to predict solute-surface affinity, and that molecular-scale surface chemical patterning significantly influences affinity-suggesting design opportunities for water purification membranes and other engineered interfaces involving aqueous solute-surface interactions.
Key words

Full text: 1 Collection: 01-internacional Database: MEDLINE Type of study: Prognostic_studies Language: En Journal: Proc Natl Acad Sci U S A Year: 2021 Document type: Article

Full text: 1 Collection: 01-internacional Database: MEDLINE Type of study: Prognostic_studies Language: En Journal: Proc Natl Acad Sci U S A Year: 2021 Document type: Article