Ultrathin, Biomimetic, Superhydrophilic Layers of Cross-Linked Poly(phosphobetaine) on Polyethylene by Photografting

Abstract

Ultrathin, biomimetic, superhydrophilic hydrogel layers, composed of cross-linked poly(2-methacryloyloxyethyl phosphorylcholine), are formed on low-density polyethylene films via ultraviolet-initiated surface graft polymerization. The layers are 19-58 nm thick as revealed by electron microscopy and have three-dimensional networks; the unique network structure, along with its zwitterionic nature, rather than surface roughness results in superhydrophilicity, that is, the water contact angle around 5°. This superhydrophilicity depends on a variety of factors, including the concentration of the monomer and cross-linker, the type of reaction solvents, the reaction and drying time, the intensity of UV light, and the way of measurement of water contact angles. Superhydrophilicity is obtained under a fixed ratio (e.g., 1/1) of the monomer to cross-linker, a reaction time over 120 s, a short drying time, (75%) ethanol as the reaction solvent, and low-intensity UV light, largely because these factors together generate optimal three-dimensional networks of cross-links.

Cleaning of Oil Fouling with Water Enabled by Zwitterionic Polyelectrolyte Coatings: Overcoming the Imperative Challenge of Oil–Water Separation Membranes

“…(Scheme 1 and Figure S1). In agreement with a previous report, 33 the PMPC surface is highly hydrophilic with water contact angle in air (WCA-A) of only ca. 3°, which is even comparable to the renowned hydrophilic surfaces of Si wafers that are freshly cleaned by Piranha solution (Si-OH) and textured hydrophilic surfaces exampled by steel supported ZnO nanostructures (Nano-ZnO) 34 (Figure 1a and Figure S2).…”