Dependence of cellulose dissolution in quaternary ammonium-based ionic liquids/DMSO on the molecular structure of the electrolyte

Marc Kostag; Omar A El Seoud

doi:10.1016/j.carbpol.2018.10.055

Dependence of cellulose dissolution in quaternary ammonium-based ionic liquids/DMSO on the molecular structure of the electrolyte

Carbohydr Polym. 2019 Feb 1:205:524-532. doi: 10.1016/j.carbpol.2018.10.055. Epub 2018 Oct 29.

Authors

Marc Kostag¹, Omar A El Seoud²

Affiliations

¹ Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil. Electronic address: marc_kostag@usp.br.
² Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, SP, Brazil. Electronic address: elseoud.usp@gmail.com.

PMID: 30446136
DOI: 10.1016/j.carbpol.2018.10.055

Abstract

We synthesized a series of quaternary ammonium acetates (QAAcOs) and assessed their solutions in DMSO as cellulose solvents. N_Bz111AcO/DMSO did not dissolve cellulose; substitution of its methyl groups resulted in efficient cellulose solvents; N_Bz31AcO/DMSO dissolved cellulose with difficulty. We attribute the inefficiency of both QAAcOs to: strong anion-cation interactions, N_Bz111AcO; steric effects and cation-cation hydrophobic interactions, N_Bz31AcO. Using isothermal titration calorimetry, we determined the enthalpies (H^E) of QAAcO (endothermic) dissolution, and QAAcO/cellobiose (exothermic) interactions; both in dimethyl sulfoxide/acetonitrile. The ratios of H^E are 5.34:1:1.45, for N_Bz111AcO, N_Al2Bz1AcO, and N_Bz31AcO, respectively, i.e., dissolution of the first and third QAAcO in the solvent requires more energy. The corresponding ratios for QAAcO interaction with cellobiose are: 0.74:1:0.79, i.e., the second QAAcO interacts more strongly with cellobiose. This order of solvent efficiency is corroborated by SEM images of regenerated cotton linters. Light scattering showed that dissolved cellulose can be regenerated as nanoparticles by dialysis.

Keywords: Cellulose dissolution; Cellulose nanoparticles; Ionic liquids; Isothermal titration calorimetry; Organic electrolyte solutions; Quaternary ammonium acetates.