Antifouling Coatings from Glassy Polyelectrolyte Complex Films

Abstract

Coatings that prevent or decrease fouling are sought for many applications, including those that inhibit the attachment of organisms in aquatic environments. To date, antifouling coatings have mostly followed design criteria assembled over decades: surfaces should be well/strongly hydrated, possess low net charge, and maintain a hydrophilic character when exposed to the location of use. Thus, polymers based on ethylene glycol or zwitterionic repeat units have been shown to be highly effective. Unfortunately, hydrated materials can be quite soft, limiting their use in some environments. In a major paradigm shift, this work describes glassy antifouling films made from certain complexes of positive and negative polyelectrolytes. The dense network of electrostatic interactions yields tough materials below the glass transition temperature, T g , in normal use, while the highly ionic character of these polyelectrolyte complexes ensures strong hydration. The proximity of equal numbers of opposite charges within these complexes mimics zwitterionic structures. Films, assembled layer-by-layer from aqueous solutions, contained sulfonated poly(ether ether ketone), SPEEK, a rigid polyelectrolyte that binds strongly to a selection of quaternary ammonium polycations. Layer-by-layer buildup of SPEEK and polycations was linear, indicating strong complexes between polyelectrolytes. Calorimetry also showed that complex formation was exothermic. Surfaces coated with these films in the 100 nm thickness range completely resisted adhesion of the common flagellate green algae, Chlamydomonas reinhardtii, which were removed from surfaces at a minimum applied flow rate of 0.8 cm s −1 . The total surface charge density of adsorbed cations, determined with a sensitive radioisotopic label, was very low, around 10% of a monolayer, which minimized adsorption driven by counterion release from the surface. The viscoelastic properties of the complexes, which were stable even in concentrated salt solutions, were explored using rheology of bulk samples. When fully hydrated, their T g values were observed to be above 75 °C.

Novel Antifouling Coatings by Zwitterionic Silica Grafting on Glass Substrates

“…Various functionalization methods can generate zwitterionic coatings with diverse thicknesses. Zwitterionic SAMs, for instance, can have thicknesses as minimal as 1 nm. , ATRP can yield thicker coatings, reaching tens of nanometers. ,− Zwitterionic coatings constructed through layer-by-layer assembly can achieve thicknesses exceeding 100 nm. , Initiated chemical vapor deposition can produce zwitterionic antifouling coatings with thicknesses extending into hundreds of nanometers. , The antifouling performance of zwitterionic coatings is closely related to the coating thickness . While zwitterionic SAMs demonstrate robust resistance to protein adsorption, their sustained prevention of attachment to mammalian cells encounters challenges.…”

Ag2O-Containing Biocidal Interpolyelectrolyte Complexes on Glass Surfaces—Adhesive Properties of the Coatings

“…This value overcomes 118 pN—the limiting value of the experimental setup. It is generally accepted that adsorption of the polycation at the glass surface is irreversible due to high electrostatic binding constant [ 55 , 56 , 57 ]. With the help of the optical tweezer, we have demonstrated that the interaction force could be quantified and that the electrostatic binding is not the only factor that ensures strong adhesion of the polyelectrolyte.…”