Imidazolium-based ionic liquid–assisted processing of natural biopolymers containing amine/amide functionalities for sustainable fiber production

In recent times, natural biopolymers have attracted considerable interest for sustainable fiber development due to their renewability and a wide degree of functionalities that allow mechanical properties and biodegradability to be modulated for intended applications. However, there remains a substantial challenge in the extraction process of natural biopolymers using conventional solvents owing to their heterogeneous molecular bonding. Ionic liquids (ILs) have proved themselves to be superior to conventional solvents in terms of extraction efficiency with added benefits of recyclability and reusability. Especially, imidazolium-based ionic liquids (IILs) have gained recognition as excellent solvents for processing natural biopolymers containing amine/amide functionalities due to their tunable structure, ease of synthesis, and favorable physicochemical characteristics such as low melting point and thermal stability. The influence of IILs along with temperature at the time of dissolution and effect of additives on the extraction of polyamines and polyamides are elaborated in this review. The role of molecular structure and viscosity of IILs on spinnability of biopolymer-IIL solutions is also highlighted in this work. Of special interest to this review are the micro/nanofiber forming ability of the biopolymer-IIL solutions using different spinning techniques and processing parameters. Finally, current challenges of fiber fabrication using IILs and their commercial opportunities in textile and biomedical industries are discussed.