Access to Highly Tough Hydrogels by Polymer Modules for Application of Catalytic Reactors

The present work shows how highly tough hydrogels can be prepared through a simple freeze–thaw–annealing approach and can be organized into robust Fenton reactors for in situ catalytic degradation of organic dyes. Hydrogels, as a kind of tissue-like materials, have been of great interest in recent decades. However, their underwhelming mechanical properties dramatically limit their applications. Here, highly tough hydrogels are obtained through a simple freeze–thaw–annealing approach using polymer modules, and are fabricated into Fenton reactors for in situ catalytic degradation of organic dyes. The associated polymer modules are poly­(vinyl alcohol) (PVA) and poly­(acrylic acid) (PAA). Upon a freeze–thaw–annealing treatment on the mixture of PVA and PAA, well-organized PVA crystal structures and unexpected ester groups between PVA and PAA are formed, resulting in highly tough hydrogels rivaling biological tissues. Moreover, upon the addition of Fe³⁺, further reinforced hydrogels were obtained, which remain intact in aqueous media even with vigorous stirring. As a proof-of-concept, these Fe³⁺-loaded tough hydrogels are molded into renewable Fenton reactors for in situ catalytic degradation of organic dyes. This study not only shows a simple approach toward highly tough hydrogels but also suggests a new concept of soft material-based chemical reactors.