Tough and multi-responsive hydrogels based on core-shell structured macro-crosslinkers

Novel hydrogels based on core-shell structured macro-crosslinkers were synthesized, which exhibited high toughness and multiple responsiveness. Sodium dodecyl sulfate (SDS) micelles mediated by NaCl were used to encapsulate hydrophobic stearyl methacrylate (C18) in the core, and hydrophilic 2-acrylamido-2-methyl-1-propanesulfonic (AMPS) monomers in the corona. Such core-shell micelles were simultaneously copolymerized with acrylamide monomers through free radical polymerization. As a result, hydrogels crosslinked by amphiphilic "poly(C18)-PAMPS" macro-crosslinkers were obtained. These hydrogels showed excellent tensile and compression strength and toughness. Cyclic compression loading-unloading tests demonstrated that the hydrogels were of outstanding fatigue resistance, and showed partial damage of energy dissipation mechanism. The damaged energy dissipation mechanism could be recovered at room temperature and the recovery could be accelerated at elevated temperatures. The hydrogels were sensitive to the change in pH and ion strength, showing reversible swelling/deswelling behaviors.