Formation of Uniform Multi-Stimuli-Responsive and Multiblock Hydrogels from Dialdehyde Cellulose

Abstract

Multi-stimuli-responsive and structured hydrogels represent promising materials with a broad application spectrum, such as drug delivery, sensors, and bionic machinery. However, the preparation of hydrogels starting from highly reactive compounds still needs an efficient approach for homogeneous distribution of each component within hydrogels. In addition, a method for in situ preparation of multiblock hydrogels is still lacking. Herein, we report the formation of uniform, multi-stimuli-responsive, and multiblock hydrogels via a novel, simple, but very efficient method by aerating ammonia gas into the solution of dialdehyde cellulose (DAC) with cross-linkers containing diamine groups. Obtained hydrogels exhibited uniform microscopic and chemical structure. Due to abundant aldehyde groups on DAC chains, diverse diamines can be used for the preparation of distinct stimuli-responsive hydrogels. For instance, 1,6-hexanediamine dihydrochloride and cystamine dihydrochloride formed hydrogels responsive to pH values as well as redox conditions. Moreover, the process of aerating ammonia gas (NH3 gas) is controllable, which allows the in situ formation of multiblock hydrogels. By using cystamine dihydrochloride, aminoethyl rhodamine spiroamide, and fluorescein isothiocyanate as reaction counterparts, 3-block hydrogels were prepared, and each block was specifically responsive to factors such as pH variation, redox condition, and/or UV illumination.