High-Toughness Polycation Cross-Linked Triblock Copolymer Hydrogels

Poly(methyl methacrylate)-poly(methacrylic acid)-poly(methyl methacrylate) (PMMA-PMAA-PMMA) triblock copolymers can self-assemble into well-defined elastic hydrogels in water by forming glassy PMMA micelle cores connected with PMAA bridges. The stiffness and toughness of these hydrogels are enhanced substantially by introducing partially quaternized poly(4-vinylpyridine) (QVP) into the system. Interactions between the QVP and PMAA molecules provide an energy dissipation mechanism, with fracture energies in excess of 1000 J/m² obtained in some cases. The materials are fully self-assembled and are formed by exposing liquid solutions in DMSO to small amounts of water. The simplicity of gel formation, and the ability to adjust the chemical and physical characteristics of these materials over a wide range, make them excellent model systems for fundamental investigations of the mechanical response of ion-containing gels.