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Preferential interactions between lithium chloride and glucan chains in N,N-dimethylacetamide drive cellulose
Adam S Gross1, Alexis T Bell, Jhih-Wei Chu
1Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, California 94720, USA.
The Journal of Physical Chemistry. B
|February 28, 2013
Summary
Lithium chloride (LiCl) in N,N-dimethylacetamide (DMA) dissolves cellulose by Li(+) cations and Cl(-) anions interacting strongly with glucan chains. Li(+) cations are key, effectively breaking cellulose
Area of Science:
- Materials Science
- Polymer Chemistry
- Computational Chemistry
Background:
- Cellulose, a crystalline biopolymer, exhibits poor solubility in common solvents due to strong interchain interactions.
- Lithium chloride (LiCl) in N,N-dimethylacetamide (DMA) is a known solvent system for dissolving cellulose.
Purpose of the Study:
- To elucidate the molecular mechanism behind cellulose dissolution in the LiCl/DMA solvent system.
- To identify the specific roles of Li(+) cations, Cl(-) anions, and DMA in the dissolution process.
Main Methods:
- Utilized all-atom molecular dynamics (MD) simulations.
- Employed reaction path optimization and free-energy calculations.
- Conducted force-matching analysis of coarse-grained atomistic simulations.
Main Results:
- DMA-mediated preferential interactions between Li(+) and Cl(-) ions and glucan chains enable cellulose dissolution.
- Weak solvation by DMA leads to strong effective interactions between ions and glucans.
- Small Li(+) cations effectively couple to multiple sites on glucan chains, including ether linkages, driving dissolution.
Conclusions:
- Li(+) cations are the primary drivers of cellulose dissolution in LiCl/DMA.
- The deduced mechanism aligns with empirical observations of cellulose solubility in salt/amide systems.
- Provides a molecular-level understanding of cellulose-solvent interactions.
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