issolution of Silk Fibroin in Mixtures of Ionic Liquids and Dimethyl Sulfoxide: On the Relative Importance of Temperature and Binary Solvent Compositio

Author(s)

El Seoud, Omar A. ^[1] ; Kostag, Marc ^[1] ; Possidonio, Shirley ^[2] ; Dignani, Marcella T. ^[1] ; Pires, Paulo A. R. ^[1] ; Lourenco, Matheus C. ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Chem, BR-05508000 Sao Paulo - Brazil

^[2] Univ Fed Sao Paulo, Inst Environm Chem & Pharmaceut Sci, Dept Chem, BR-04021001 Sao Paulo - Brazil

• Document type: Journal article
• Source: POLYMERS; v. 14, n. 1 JAN 2022.
• Web of Science Citations: 0

Abstract

We studied the dependence of dissolution of silk fibroin (SF) in mixtures of DMSO with ionic liquids (ILs) on the temperature (T = 40 to 80 degrees C) and DMSO mole fraction (chi(DMSO) = 0.5 to 0.9). The ILs included BuMeImAcO, C(3)OMeImAcO, AlBzMe(2)NAcO, and Bu4NAcO; see the names and structures below. We used design of experiments (DOE) to determine the dependence of mass fraction of dissolved SF (SF-m%) on T and chi(DMSO). We successfully employed a second-order polynomial to fit the biopolymer dissolution data. The resulting regression coefficients showed that the dissolution of SF in BuMeImAcO-DMSO and C(3)OMeImAcO-DMSO is more sensitive to variation of T than of chi(DMSO); the inverse is observed for the quaternary ammonium ILs. Using BuMeImAcO, AlBzMe(2)NAcO, and molecular dynamics simulations, we attribute the difference in IL efficiency to stronger SF-IL hydrogen bonding with the former IL, which is coupled with the difference in the molecular volumes and the rigidity of the phenyl ring of the latter IL. The order of SF dissolution is BuMeImAcO-DMSO > C(3)OMeImAcO-DMSO; this was attributed to the formation of intramolecular H-bonding between the ether oxygen in the side chain of the latter IL and the relatively acidic hydrogens of the imidazolium cation. Using DOE, we were able to predict values of SF-m%; this is satisfactory and important because it results in economy of labor, time, and material. (AU)

• FAPESP's process: 16/22869-7 - Novel solvents in cellulose chemistry: synthesis, properties, and application of quaternaryammonium electrolytes for dissolution, regeneration, and derivatization of cellulose
• Grantee: Marc Kostag
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/22136-4 - Use of green solvents and their mixtures for optimizing chemical processes
• Grantee: Omar Abou El Seoud
• Support Opportunities: Research Projects - Thematic Grants