Interactions of NaCl with cellulose Iβ crystal surfaces and the effect on cellulose hydration: a molecular dynamics study

Zhennan Kou, Dmitry Tolmachev, Maisa Vuorte, Maria Sammalkorpi*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Crystalline nanocellulose is widely used for example, in the paper-making and food industries, as support matrix material or reinforcement of polymer materials, but also in drug carrier and nanomedicine applications. Interestingly, aqueous solutions of cellulose are extremely sensitive to small amounts of added salt yet mere considerations of charge screening leave open questions regarding the mechanisms, especially for unmodified cellulose in aqueous solutions. Here, we map NaCl ion distributions and the effect of added NaCl salt on the hydration of Iβ cellulose nanocrystal (CNC) surfaces by atomistic detail molecular dynamics simulations with explicit water solvent. The simulations reveal the dependency of the hydration layers of the six surfaces of CNCs on the ions, as well as NaCl ion binding sites, and preferences in terms of binding free energy for the ions near CNC surfaces at different NaCl concentrations. We discuss the modelling results against our prior rheology characterization of cellulose solutions. Together, the results indicate that the high sensitivity of cellulose aqueous solutions to added salt rises from the ions near the surface changing locally the ordering and structure of the hydration layers of the CNC surfaces. The revealed mechanism of salt-induced viscosity changes in cellulose aqueous solutions allows advanced design of gelling CNC systems for various end uses and may also guide tuning cellulose interactions by different solvent environments.

Original languageEnglish
Pages (from-to)4115-4129
Number of pages15
JournalCellulose
Volume31
Issue number7
Early online date30 Mar 2024
DOIs
Publication statusPublished - May 2024
MoE publication typeA1 Journal article-refereed

Keywords

  • Cellulose
  • CNC
  • Hydration
  • Hydrogel
  • Molecular dynamics
  • Nanocellulose
  • Salt effects

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