Abstract

To date, chitosan (CS) is the most investigated biopolymer due to its interesting physicochemical features and versatility in several applications. Due to its multiple chemical functionalities and adaptable ability toward several shapes, structures, materials and networks, CS is still explored by the research community and extends it to new applications. In this regard, deep eutectic solvents (DESs), a new generation of green solvents and additives, have recently been investigated in tuning the properties of CS derived materials and structures. In starting pioneering works, the use of DES was mainly focused on their complete blending with CS phases to generate fully miscible non-porous structured materials. However, the versatility of DES systems, depending on their nature, has turned into tailoring CS networks into highly porous structures with adjusted porosities according to the target application. The role of the DES in customizing CS structures has evolved from producing non-porous to the design of highly porous structures. Therefore, this review paper lays out the core successful applications of implementing distinct types of DESs into CS networks to improve specific properties (such as encapsulation capacity, drug delivery ability, mechanical and thermal stability, water absorption, porosity, tuned hydrophobicity, adhesive and self-healable properties, among others) in the resulting customized structures, including flat non-porous structures, eutectogels, aerogels, beads, monoliths, among other derivative structures. Apart from elucidating the modification protocols of CS networks assisted by DESs, we also pinpoint the key interactions between the polymer and the DES system, resulting in the desired structure. In addition, we also provide key findings on the role of DES in the chemical functionalization, quaternization, methylation and polymerization reaction of specific CS derivatives. After revising the current literature, we finally declare perspectives and future scopes of research in the field.