Hydrogels Based on Cellulose and its Derivatives: Applications, Synthesis, and Characteristics

Hydrogels are mainly structures formed from biopolymers and/or polyelectrolytes, and contain large amounts of trapped water. Smart cellulose-based superabsorbent hydrogels are the new generation of scaffold which fabricated directly from native cellulose (including bacterial cellulose) via cellulose dissolution. Cellulose has many hydroxyl groups and can be used to prepare hydrogels with fascinating structures and properties. Cellulose hydrogels based on its derivatives, including methyl cellulose (MC), hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), and carboxymethyl cellulose (CMC) can be fabricated by various methods. On the basis of the cross-linking method, the hydrogels can be divided into chemical and physical gels. Physical gels are formed by molecular self-assembly through ionic or hydrogen bonds, while chemical gels are formed by covalent bonds. Composite smart hydrogels are prepared using cellulose in conjunction with other polymers through blending, formation of polyelectrolyte complexes, and interpenetrating polymer networks (IPNs) technology. According to type of superabsorbent cellulose-based hydrogels fabrication methods, there are many various techniques to evaluate quality of them. Briefly, some of these means generally used to assess the hydrogel are described as following. The obtained gel membranes are characterized by infrared spectroscopy, scanning electron microscopy, thermo gravimetric analysis, and mechanical tests in order to investigate the crosslinking occurrence and modifications of cellulose resulting from the synthetic process, morphology of the hydrogels, their thermal stability, and viscoelastic extensional properties, respectively. This review highlights the recent progress in smart cellulose-based superabsorbent hydrogel designs, fabrication approaches and characterization methods, leading to the development of cellulose based smart superabsorbent hydrogels.