A review of the strategies used to produce different networks in cellulose-based hydrogels

Polymeric hydrogels are crosslinked networks that form three-dimensional materials, offering unique tailored properties and diverse applications. Cellulose is a natural biopolymer abundant in hydroxyl groups, which holds great potential for hydrogel synthesis via chemical and physical crosslinking. Cellulose-based hydrogels possess potential advantageous characteristics, which enable their use in several fields, such as environmental, medical, agriculture, and most recently in energy fields. Nevertheless, challenges related to mechanical properties and degradation of these polymers persist. To address these limitations, the incorporation of multiple networks in cellulose hydrogels has been explored, combining the desirable features of each type of network to enhance overall performance. Hydrogels can be classified into various types of networks, including single crosslinking (physical or chemical), double-crosslinked hydrogels, grafted hydrogels, semi-interpenetrating polymeric networks (semi-IPN), and interpenetrating polymeric networks (IPN). Exploring the different network types that a hydrogel can form is a way to improve its characteristics regarding mechanical properties, temperature stability, morphological structure, stimuli-responsive behavior, and swelling and release kinetics of active compounds incorporated in it. The intricate nature of interactions within cellulose hydrogels poses a challenge to grasping the nuanced differences in strategies employed to create each unique network. Therefore, this manuscript elucidates the differences between the main types of networks that can be created in cellulose hydrogels, their synthesis methods, benefits, and limitations, serving as a valuable resource to guide future research about cellulose-based hydrogels.