Growth of Double-Network Tough Hydrogel Coatings by Surface-Initiated Polymerization

Hydrogel coatings exhibit versatile applications in biomedicine,
flexible electronics, and environmental science. However, current
coating methods encounter challenges in simultaneously achieving strong
interfacial bonding, robust hydrogel coatings, and the ability to
coat substrates with controlled thickness. This paper introduces a
novel approach to grow a double-network (DN) tough hydrogel coating
on various substrates. The process involves initial substrate modification
using a silane coupling agent, followed by the deposition of an initiator
layer on its surface. Subsequently, the substrate is immersed in a
DN hydrogel precursor, where the coating grows under ultraviolet (UV)
illumination. Precise control over the coating thickness is achieved
by adjusting the UV illumination duration and the initiator quantity.
The experimental measurement of adhesion reveals strong bonding between
the DN hydrogel coating and diverse substrates, reaching up to 1012.9
J/m2 between the DN hydrogel coating and a glass substrate.
The lubricity performance of the DN hydrogel coating is experimentally
characterized, which is dependent on the coating thickness, applied
pressure, and sliding velocity. The incorporation of 3D printing technology
into the current coating method enables the creation of intricate
hydrogel coating patterns on a flat substrate. Moreover, the hydrogel
coating’s versatility is demonstrated through its effective
applications in oil–water separation and antifogging glasses,
underscoring its wide-ranging potential. The robust DN hydrogel coating
method presented here holds promise for advancing hydrogel applications
across diverse fields.