Across our suite of standards, the data reveals enhanced surface activity of the dimer species when compared to their monomer precursors. We began our investigations by conducting a comparison between ent-pinonaldehyde (ent-2) and its corresponding aldol dimer 7. At 0.1 mM in 1.0 M ammonium sulfate, the aldol addition dimer 7 exhibited a relative surface tension depression roughly 9% greater than its monomer precursor pinonaldehyde (ent-2) at the same concentration (Figure ). Even when measured at 1.0 mM, a concentration ten times that of the dimer species, none of the α-pinene derived monomer species measured in a previous study showed a greater surface tension depression than the dimers measured here (pinonaldehyde showed only an 8.6% decrease at 1.0 M in 1.0 M ammonium sulfate). The propensity of the dimers to populate the droplet surface is in agreement with studies which have observed a "crusting effect," wherein during liquid liquid phase separation (LLPS) oligomers populate the surface of particles and over time form a shell-like structure. The significant difference in surface tension suppression observed between the monomeric aldehyde ent-2 and its dimeric adduct 7 also serves to highlight the limitations of correlating O:C ratios of compounds with physical properties, a practice that is common in the field of atmospheric science. Our comparison here shows clearly that two species with identical O:C ratio can have dramatically different climate-relevant properties.