Organic films on ocean and lake surfaces as well as on aqueous atmospheric aerosols affect a wide range of important processes, from water evaporation and condensation to light scattering to heterogeneous chemistry. Using molecular dynamics simulations, we studied palmitic acid (CH3(CH2)14COOH) and hexadecanol (CH3(CH2)15OH) monolayers on water to obtain atomistic level insight into the intermolecular interactions and structural characteristics as a function of surface density. The observed trends in ordering and packing of the monolayer molecules correspond well to known experimental results. In addition, we performed MD simulations of model multi-component monolayers, more representative of the naturally occurring complex surfactant films. The model systems were prepared so as to mimic the changes in the film composition due to oxidation of the monolayer molecules. MD simulations revealed structural changes of the monolayer triggered by oxidation, including orientational reversal of oxidized chains and transient accumulation of volatile oxidation products in the monolayer.

Molecular dynamics simulations of organic films at the air/water interface

243rd National Meeting (2012)

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