Molecular partitioning in ternary solutions of cellulose

Xin Zhang; Yimin Mao; Madhusudan Tyagi; Feng Jiang; Doug Henderson; Bo Jiang; Zhiwei Lin; Ronald L Jones; Liangbing Hu; Robert M Briber; Howard Wang

doi:10.1016/j.carbpol.2019.05.054

Molecular partitioning in ternary solutions of cellulose

Carbohydr Polym. 2019 Sep 15:220:157-162. doi: 10.1016/j.carbpol.2019.05.054. Epub 2019 May 23.

Authors

Affiliations

¹ Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, United States.
² Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, United States; NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, United States.
³ Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, United States.
⁴ Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, United States; Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, United States. Electronic address: wangh@umd.edu.

PMID: 31196535
DOI: 10.1016/j.carbpol.2019.05.054

Abstract

Neutron scattering measurements on the structure and dynamics of ternary solutions of microcrystalline cellulose (MC) in mixtures of an ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate and a polar organic solvent dimethylformamide (DMF) have shown that MC can be fully dissolved in solvent mixtures. Data also show the molecular partitioning of IL into coexisting states. The structure partitioning is manifested as IL adsorbed to cellulose molecules with additional IL self-assembled to form clusters in solution, while the dynamics partitioning shows dynamical heterogeneities of the IL with slow dynamics resembling neat IL and fast dynamics being coupled with the solvent. The composition dependence of the molecular partitioning results in a solubility gap in dilute cellulose solutions and a phase boundary criterion of the molar ratio of IL / MC ∼ 3 in more concentrated regimes. The two characteristics together define the main features of the dissolution phase diagram of ternary cellulose mixtures of MC / IL / DMF at the room temperature.

Keywords: Cellulose; Ionic liquid; Molecular solution; Neutron scattering; Phase diagram.