A Simple Poly(Vinyl Sulfonate) Coating for All‐Purpose, Self‐Cleaning Applications: Molecular Packing Density–Defined Surface Superhydrophilicity

Abstract In this study, poly(vinyl sulfonate) (PVS)–capped surfaces are constructed on the polyelectrolyte multilayers (PEMs) of poly(diallyldimethylammonium chloride) and poly(styrene sulfonate) via electrostatic assembly. The water wetting behavior on the resulting PVS‐capped PEMs is meticulously correlated with the number of surface sulfonate groups with the aid of sum frequency generation spectroscopy and quartz crystal microbalance. It is found that when the molecular packing density of surface sulfonate groups is adjusted to be comparable to the maximal packing density of spheres in two dimensions (≈0.9), the PVS capping is able to effectively adsorb water molecules from the surrounding to form hydrogen‐bonded networks, which not only promote complete surface wetting by water in air but also diminish surface affinity to adhesion of ice, oil and wax deposited atop. As a result, the PVS‐capped PEMs are able to fulfil all the self‐cleaning functions proposed for superhydrophilic surfaces including anti‐fogging, anti‐icing, anti‐grease, anti‐smudge, anti‐graffiti, and anti‐wax. After being coated with the self‐cleaning PVS‐capped PEMs, conventional stainless steel meshes are able to perform oil‐water separation without prior water wetting.