Poly(acrylic acid)-catalyzed supramolecular self-assembly enables free-standing low-molecular-weight hydrogels

Supramolecular hydrogels self-assembled by low-molecular-weight gelators through non-covalent interactions present potent application potential in fields ranging from biomedicine to energy. However, the underwhelming mechanical properties dramatically limit real-life applications. In this contribution, we report our access to free-standing supramolecular hydrogels by triggered self-assembly of gelators using polyacrylic acid (PAA) as a catalyst. This is achieved using a hydrazone formation-induced self-assembly system, where the formation and self-assembly of hydrazone-based gelators can be dramatically accelerated under the catalysis of acid. The addition of PAA dramatically accelerates the hydrogelation process, resulting in hydrogels exhibiting well-defined networks and high stiffness. Under optimal conditions, the stiffness can even reach 37.5 kPa compared to only 2.9 kPa for the pure hydrogel. Furthermore, we find that the resultant hydrogels can stand freely and can be remolded in various shapes. Our study presents a simple approach towards strong supramolecular hydrogels that can retain their shape and size while maintaining the functionalities and stability, accelerating the applications of supramolecular hydrogels in the field of, for instance, biosensors, tissue engineering, and drug delivery.