High-Strength and Tough Acid-Base Complex Hydrogels with Memory-Forgetting and Shape-Memory Features.

Complexes associated with strong electrostatic interactions constitute a valuable method to construct tough hydrogels, but current systems are either unstable in saline environments or lead to relatively soft matrices. Herein, a class of acid-base complex (ABC) hydrogels made from poly(2-(dimethylamino)ethyl methacrylate) and glassy poly(methacrylic acid) (PMA) is reported. The tough hydrogels are prepared via a dialysis-free process and maintain their structure in saline solutions. Results indicate that the glassy feature of PMA endows the ABC hydrogels with high moduli (227 MPa), typical yielding points (3 MPa), and moderate stretchability (300% strain). The glassy backbones (PMA chains) are stiff at low temperatures, and would be melted at high temperatures, which bring about interesting shape-memory effects and inverse memory-forgetting behaviors. These results may inspire a simple but powerful strategy to design innovative hydrogel materials.