Ionic cellulose derivatives: Charge design and advanced applications

Increasing environmental concerns highlight the need to transition from petroleum to renewable, sustainable resources for the fabrication of carbon-neutral products. Cellulose, the most abundant natural polysaccharide on Earth, serves as a fundamental structural component in plants and offers immense potential for a wide range of human applications. Moving beyond conventional dissolution-regeneration processes, the ionic modification of cellulose has emerged as a key strategy to enhance its functionality. This approach yields derivatives that can be categorized into anionic, cationic, and zwitterionic/amphoteric types, many of which are already widely commercialized. Beyond differences in the polarity of the charged groups, variations in their interactions with ions and molecules confer distinct functionalities. Therefore, this review systematically summarizes the types and structures of various ionic cellulose derivatives (including nanocellulose), outlining typical ionic modification routes including oxidation, esterification, etherification, and grafting reactions that target hydroxyl groups on the cellulose backbone. We further examine the charge-governed properties of these materials, such as biological activity, surface wettability, stimulus responsiveness, ion exchange capacity, ion regulation, and energy dissipation. Notably, this review places emphasis on analyzing how these properties determine performance across diverse applications, including biomedical engineering, energy storage/conversion, environmental remediation, sensors, and actuators. Finally, we identify current challenges in the field and outline future opportunities for the rational design and advanced application of ionic cellulose derivatives. We hope this review will bridge the gap between ionic cellulose derivatives and their practical applications.