Heterogeneous ice nucleation (IN), prompted by organic material, is fundamental for understanding cloud formation and the global radiative budget. Numerous surfactant species at the sea surface microlayer (SSML) appear to contribute to IN. It has been shown that fatty alcohols are often effective ice nucleators whereas fatty acids appear to be weak ice nucleators. Here we investigate the molecular interactions and organization of stearic acid (C18 acid) and stearyl alcohol (C18 alcohol) films at varied temperatures through surface potential (related to the interfacial electric field) measurements upon film compression. Surface potential provides information regarding hydration effects and water dipole orientation induced by the surface-active substances. Results show that the surface potential increases as temperature decreases and that the maximum surface potential achieved is higher for the fatty alcohol than the fatty acid indicative of larger dipole contributions. Interestingly, at low surface coverage, the fatty acid has a higher surface potential than the fatty alcohol.

Surface potential of aqueous fatty acid and alcohol surfaces: Understanding temperature effects and ice nucleation

2019 Fall National Meeting

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