Recent advances in polysaccharide-based ionogels

Ionogels are gel materials consisting of ionic liquids as the dispersed phase immobilized by organic or inorganic networks as the matrix，which have attracted extensive attention owing to their characteristic ionic conductivity，thermal and electrochemical stability，non-volatility，and liquid-solid biphasic properties.However，the ionogels prepared by conventional synthetic polymers have issues with biocompatibility，biodegradability，regeneration，and poor mechanical properties，which are difficult to meet the requirements of ecological environmental protection and complex application scenarios.Polysaccharide-based ionogels have not only good biocompatibility and biodegradability，but also unique physical and chemical properties due to the special molecular structure and rich functional groups of polysaccharide molecules，which show great application potential in many fields.Specifically，the polysaccharides backbone contains a large number of functional groups，which can directly participate in the formation of dynamic covalent bonds/non-covalent bonds.It has excellent biological properties under physiological conditions and have made great contributions to the development of ionogels with excellent mechanical properties，good biocompatibility and strong adhesion.In addition，the sources of polysaccharides are wide and easy to obtain compared with other natural or synthetic hydrogel raw materials，which further promotes the development of polysaccharide-based ionogels.In this review，we focus on the recent advances in preparations and applications of ionogels based on polysaccharides （cellulose，alginate，chitosan，xanthan gum and cyclodextrin，etc.）.Firstly，the design and synthesis principles for fabricating polysaccharide-based ionogels are summarized.Ionogels are generally designed through the formation of polysaccharide-based polymer networks in an IL medium and the IL molecules are confined in the network after gelation.Secondly，polysaccharide-based ionogels that are interconnected via crosslinking strategies （e.g.，semi-interpenetrating polymer networking and interpenetrating networking） are introduced.The introduction of noncovalent and/or dynamic covalent interactions imparts polysaccharide-based ionogels with intriguing performances （e.g.，improved toughness，stimuli‑response and self-recovery，etc.）.Thirdly，the diverse applications of polysaccharide-based ionogels in polymer electrolytes，wearable soft sensors，drug delivery，wound healing，tissues engineering，and wastewater treatment are discussed.Finally，the perspectives of polysaccharide-based ionogels are outlined to promote their future design for new functions and applications.In conclusion，this review offers a comprehensive perspective on the recent progress of ionogels based on polysaccharides ranging from polymer electrolytes to wastewater treatment.This research area is still in its infancy.Considering the numerous ILs types and various polysaccharides networks，ionogels with new properties and applications are expected to emerge in coming years.We believe that polysaccharides-based ionogels for various applications will be commercially available in the very near future.