A universal strategy for growing multifunctional hydrogel coatings on diverse polymers via Fenton reaction

Growing hydrogel coatings in a controlled manner exhibits promising potential for various applications, but lacks a universal method especially from polymer precursors. Herein, we propose a facile yet effective strategy to controllably grow various types of hydrogel coatings, either from polymers or monomers, on diverse polymer substrates via Fenton reaction. By immersing the pretreated polymer substrate in the given precursor solution, peroxide adsorbed into/on the substrate surface and Fe²⁺ in the solution trigger continuous Fenton reaction at the solid–liquid interface to drive polymer chains interlinking to the substrate and crosslinking into a network synchronously. Furthermore, due to the high viscosity of the newly formed hydrogel, radicals are confined close to the interface by diffusion, which not only allows for precise control over the coating thickness but also enables the reutilization of precursor solution. As proof of concept, our method is successfully applied to produce hydrogel coatings with adjustable micron-scale thickness, impart excellent low-friction and antifouling properties to polymer substrates, and manipulate a series of fine hydrogel patterns. Therefore, this work presents a pioneering universal approach for growing hydrogel coatings on various polymer surfaces and implies significant potential applications.