A&P Seminar - Rebecca Rapf

Air-water interfaces are ubiquitous in natural environments and often include the presence of organic, surfactant films. The structure and morphology of these organic films can have profound impacts on material transfer between the gas and condensed phases, the optical properties of atmospheric aerosol, and chemical processing at air–water interfaces. Combined, these effects can have significant impacts on climate via radiative forcing, but our understanding of organic films at air–water interfaces is incomplete. Here, we examine the impact of the polar headgroup and alkyl tail length on the structure and morphology of organic monolayers at the air–water interfaces, using Langmuir isotherms and infrared reflection absorption spectroscopy (IR-RAS). We explore the phase behavior and film packing for a series of model organic acids, including α-keto acids, hydroxy acids, and carboxylic acids. In addition, we report on differences in the interfacial ionization of these acids, which has significant implications for how these species may be processed in the environment.