Cross-linked polysaccharide assemblies in marine gels: An atomistic simulation

Marine polymeric gels or colloidal nano- and microgels have been shown to contribute significantly to the primary marine aerosol and cloud condensation nuclei over remote marine areas. A microscopic understanding of such biologically derived matter at the sea-air interface is important for future development of global climate models, but unfortunately cannot be obtained from modern characterization techniques. In this contribution, we employ molecular dynamics simulations to reveal the atomistic details of marine polymeric gels represented by anionic polysaccharide assemblies. The ionic bonds formed between polysaccharides and metal ions in seawater as well as the hydrophobic contribution to surface area are investigated in detail, and destabilization of the assemblies upon removal of Ca²⁺ or acidification is explained. These results provide insight into physicochemical properties of polysaccharide-Ca²⁺ structures and enable future studies of their roles of in the wetting process of cloud droplet activation.