Construction of multiresponsive supramacromolecular hydrogels with a novel azobenzene derivative as crosslinkers

Supramacromolecular hydrogels (SMHGs) are attractive materials in various areas. Due to their excellent reversible photoisomerization ability, azobenzene derivatives have been widely applied to construct SMHGs. But the majority of these systems were realized only by transplanting azobenzene function groups into macromolecule chains, while low-molecular-weight (LMW) azobenzene derivatives are fairly rare. Therefore, it is highly desirable to develop facile and effective strategies for the construction of SMHG. Here, a new ABA-typed azobenzene derivative (AD) has been designed and synthesized, which can be applied as LMW crosslinkers to construct SMHGs through electrostatic interactions between AD and sodium alginate (SA). When AD is mixed with SA solution in acidic conditions, SMHGs can form at various concentrations of SA. In addition, the concentration of AD also has a large impact on the moduli values. Profiting from electrostatic interactions between AD and SA, as well as interchain hydrogen bonds of SA, SMHGs can experience sol-gel transitions under pH-, photo- or thermo-stimuli. This work contributes a simple but effective strategy for the construction of SMHGs using azobenzene derivatives as LMW crosslinkers.