Polyethylene glycol-grafted, hierarchically textured superhydrophilic silica coating with robust anti-fogging and protein-resistance

Superhydrophilic coatings are of broad interest for self-cleaning, oil–water separation, anti-fogging, and anti-biofouling applications. In this work, a transparent and mechanically robust PEG-grated superhydrophilic silica coating was fabricated on glass by combining sequential dip-coating with covalent surface functionalization. Polyethylene glycol trimethoxysilane (PEG-TMOS) was synthesized via a hydrosilylation reaction between trimethoxysilane (TMOS) and allyl polyethylene glycol (APEG). Acid-catalyzed silica (A-silica, ∼20 nm in diameter) and base-catalyzed silica (B-silica, ∼165 nm in diameter) nanoparticles were prepared through TEOS hydrolysis/condensation using HCl and NH 3 ·H 2 O, respectively. The coating was constructed by sequentially depositing A-silica and B-silica to build an adhesion-promoting interlayer and a roughness-enhancing top layer, respectively, followed by grafting PEG-TMOS on the surface of B-silica particles. Successful PEG grafting was confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and the coating achieved superhydrophilicity with a static water contact angle below 5° while maintaining high visible-light transmittance (∼95%). The coating also exhibited strong adhesion (Grade 0), pencil hardness of 3 H, and excellent abrasion durability, retaining hydrophilicity after 700 rubbing cycles. Functionally, the PEG-grafted surface remained clear under both steam (60 °C) and frost-to-ambient conditions and showed strong resistance to bovine serum albumin (BSA) adsorption. This scalable, chemistry-anchored strategy provides a practical route to high-clarity superhydrophilic coatings with durable anti-fogging and antifouling performance.