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SUMMARY:How Does Charge Impact Surface Hydrophobicity? - Camille Bilodeau\
 , University of Virginia
DTSTART:20250602T130000Z
DTEND:20250602T133000Z
UID:TALK232540@talks.cam.ac.uk
CONTACT:Isaac Parker
DESCRIPTION:Molecular-scale hydrophobicity plays a key role in many import
 ant interfacial phenomena ranging from adsorptive separations and fouling 
 to colloidal assembly and protein aggregation. While macroscopic hydrophob
 icity can be experimentally measured using a simple contact angle\, hydrop
 hobicity at molecular length-scales is difficult to quantify and depends o
 n surface chemistry and patterning in unintuitive ways. \nIn this work\, w
 e investigate the relationship between charge and hydrophobicity by studyi
 ng a series of model patterned hydrophobic and charged surfaces. To measur
 e the “hydrophobicity” of the surface\, we use two different views of 
 hydrophobicity. First\, we apply Indirect Umbrella Sampling (INDUS) an enh
 anced sampling technique that directly measures the free energy of cavity 
 formation. Second\, we perform spatial umbrella sampling to obtain a free 
 energy of binding of two model hydrophobic solutes\, a gold nanoparticle f
 unctionalized with an alkyl thiol SAM and a model hydrophobic protein\, hy
 drophobin. We show how our definition of hydrophobicity is sensitive to ho
 w we define hydrophobicity and discuss the theoretical basis for connectin
 g adsorption energetics to de-wetting thermodynamics. Using these methodol
 ogies\, we find that different positively charged groups (i.e. ammonium ve
 rsus guanidinium) impact hydrophobicity differently due to their differenc
 es in geometry\, partial charge distribution\, and number of hydrogen bond
  donor sites. We additionally find that charged group spacing plays a majo
 r role in modulating hydrophobicity\, with specific “sweet spot” dista
 nces being associated with maximizing hydrophilicity. This work lays a fou
 ndation for connecting dewetting calculations to adsorption as well as for
  understanding how charged group chemistry and patterning impact hydrophob
 icity.\n
LOCATION:Zoom: https://zoom.us/j/92447982065?pwd=RkhaYkM5VTZPZ3pYSHptUXlRS
 kppQT09
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