Long‐Range Hydrophilic Attraction between Water and Polyelectrolyte Surfaces in Oil

Abstract

The outstanding water wettability and the capability of polyelectrolyte surfaces to spontaneously clean oil fouling are determined by their wetting mechanism in the surrounding medium. Here, we have quantified the nanomechanics between three types of polyelectrolyte surfaces (i.e. zwitterionic, cationic, and anionic) and water or oil drops using an atomic force microscope (AFM) drop probe technique, and elucidated the intrinsic wetting mechanisms of the polyelectrolyte surfaces in oil and water media. The measured forces between oil drops and polyelectrolyte surfaces in water can be described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Surprisingly, strong long-range attraction was discovered between polyelectrolyte surfaces and water drops in oil, and the strongest interaction was measured for the polyzwitterion. This unexpected long-range "hydrophilic" attraction in oil could be attributed to a strong dipolar interaction because of the large dipole moment of the polyelectrolytes. Our results provide new nanomechanical insights into the development of novel polyelectrolyte-based materials and coatings for a wide range of engineering, bioengineering, and environmental applications.

Hydration lubrication of polyzwitterionic brushes leads to nearly friction- and adhesion-free droplet motion

“…Despite recent progress, there is little direct experimental evidence for the presence of the water film between the oil droplet and the substrate, and most previous discussions implicitly assume the presence of such a hydration layer. [7,8,11,12]. The thickness of this water film-should it exist-is not known and its relation to oil-repellency remains poorly understood.…”

Zwitterionic Polymer‐Grafted Superhydrophilic and Superoleophobic Silk Fabrics for Anti‐Oil Applications

“…[ 18–24 ] The zwitterionic polymers carry functional groups like carboxybetaine, sulfobetaine, phosphobetaine, etc., which have both positive and negative charge in the same monomer. [ 25 ] The strong polarity gives rise to a hydration layer around the zwitterionic polymer chains, [ 26,27 ] which can prevent the adsorption of oil droplets onto the polymer surfaces. [ 28 ] Studies have reported that copolymer hydrogels prepared by poly(ethylene glycol)diacrylate (PEGDA) and zwitterionic monomer, such as carboxybetaine methacrylate and sulfobetaine methacrylate (SBMA), demonstrate better hydrophilicity than those of PEGDA.…”

Interplays of Interfacial Forces Modulate Structure and Function of Soft and Biological Matters in Aquatic Environments

“…Recent interfacial force measurements have shown several interesting findings. Hayashi et al reported the presence of several nm-thick, repulsive layers near the bioinert oligoethylene glycol surfaces (Hayashi et al, 2012), and Shi et al demonstrated there is a long-range attraction between water and zwitterionic polymer brushes in oil (Shi et al, 2016). Further studies on the structures and dynamics of water in the vicinity of polymer/water interface potentially enable to overcome the commonly taken trial-and-error approaches toward the rational design, or even the prediction of new bioinert materials.…”