Saccharides comprise one of the largest mass fractions of organic matter in sea spray aerosol (SSA), and it is possible that anionic polysaccharide aggregates in the form of marine hydrogels contribute to this enrichment. Polysaccharides larger than 100 kDa bearing carboxylate moieties have been observed to nucleate ice, suggesting that marine gels could contribute to ice and mixed-phase cloud formation within the marine boundary layer. We probed interfacial solvation and morphology of marine hydrogels embedded in sea spray aerosol proxy films at low temperatures to better understand the molecular mechanisms responsible for heterogeneous ice nucleation in SSA. Alginate, an anionic polysaccharide rich in carboxylate moieties that gels in the presence of calcium cations, was used to model marine hydrogels in SSA. A palmitic acid monolayer was spread onto an artificial seawater solution containing alginate hydrogels at temperatures between 0°C and 21°C. Infrared reflection-absorption spectroscopy and surface tensiometry revealed that alginate exhibits greater adsorption to a palmitic acid monolayer at warmer temperatures. Alginate hydrogels likely disrupt the monolayer solvation structure and interact with the palmitic acid carboxylate headgroups. Additionally, signal enhancement between 3000 and 3200 cm<sup>-1</sup> in the presence of alginate at low temperatures suggests ice-like ordering of the interfacial water molecules. Further investigation is underway to examine the effects of pH on alginate solvation and organization in SSA proxy films.

Low temperature interfacial solvation and morphology of marine hydrogels in sea spray aerosol proxy films

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.