Tough Glassy Hydrogels of High Water Content via Polymerization‐Induced Hydrogen Bonding and Phase Separation of Block Copolymers

ABSTRACT Tough glassy hydrogels that rely on robust noncovalent interactions of copolymers typically suffer from low water content, because random monomer sequences hinder the formation of ordered intermolecular associations and well‐organized network architectures. Here, we report tough poly(methacrylic acid)‐ block ‐poly(methacrylamide) (PMAAc‐ b ‐PMAAm) hydrogels with high water content, fabricated via the reversible addition–fragmentation chain transfer (RAFT) polymerization that results in hydrogen bonding between repeated units and microphase separation of the system. The block sequence promotes formation of highly ordered and robust hydrogen bonds between PMAAc and PMAAm segments. Meanwhile, the polymerization directs phase separation and gelation into a dense bicontinuous network of distinct soft and hard domains, which undergoes vitrification without network collapse and dehydration. Consequently, the resulting hydrogels remain glassy at room temperature while retaining high water content. It exhibits a tensile modulus of up to 8.1 MPa at a water content of ∼83 wt.%, substantially exceeding those of random copolymer analogue hydrogels and most reported glassy hydrogels. Our findings elucidate how block sequence governs phase‐separated network architecture and mechanical performance of supramolecular hydrogels, providing a generalizable molecular engineering strategy for high‐performance soft materials.