Screening of ionic liquids for the dissolution of chitosan using COSMO-RS

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 26; no. 3; pp. 1577 - 1586
• Main Authors: Mok, Shue Yee, Sivapragasam, Magaret, Raja Shahrom, Maisara Shahrom, Bustam @ Khalil, Mohammad Azmi, Abidin, Zurina Zainal
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 05.02.2024
• Subjects: Activity coefficients; Amino acids; Anions; Cations; Chitosan; Dilution; Dissolution; Enthalpy; Hydrogen bonding; Ionic liquids; Molecular interactions; Pyridinium; Screening; Solvents; Thermodynamic properties; Van der Waals forces
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/d3gc03586g

The dissolution of chitosan is a tedious and time-consuming process. Herein, we select the best Ionic Liquids (ILs) for chitosan dissolution through the application of Conductor-like Screening Model for Real Solvents (COSMO-RS), which allowed the screening of 640 ILs based on 32 cations based on amino acids, imidazolium, pyridinium, and pyrrolidinium, and 20 selected anions such as [C 2 H 3 O 2 ], [Cl], [NO 3 ], [BF 4 ], and others. Thermodynamic properties such as logarithmic activity coefficient at infinite dilution (ln  γ ) and excess enthalpy (H E ) were used to evaluate the dissolution potential of ILs towards chitosan, whereby low values of ln  γ and H E indicated better engagement between the solute and the solvent, thus resulting in a higher solute being dissolved. A preliminary screening of chitosan dissolution was carried out in all 5 synthesized ILs to validate the results obtained by COSMO-RS. It was observed that ILs with [BF 4 − ] as the anion and cations such as [Ser], [Gly], [Phe], [Cys], and [Asn] have the lowest ln  γ values, hence better interaction with chitosan. The values of H E indicated that the molecular interactions between chitosan and ILs were governed by hydrogen bonding (ranging from 37 to 50%), followed by misfit interactions (ranging from 21 to 31%) and van der Waals forces (ranging from 22 to 32%) due to the abundance of hydroxyl (-OH) groups present in the intermolecular and intramolecular chitosan structures. These proved the great ability of COSMO-RS to accurately predict the dissolution of chitosan in ILs. The dissolution of chitosan is a tedious and time-consuming process.