Statistical thermodynamics unveils the dissolution mechanism of cellobiose

Abstract

In the study of the cellulose dissolution mechanism opinion is still divided. Here, the solution interaction components of the most prominent hypotheses for the driving force of cellulose dissolution were evaluated quantitatively. Combining a rigorous statistical thermodynamic theory and cellobiose solubility data in the presence of chloride salts, whose cations progress in the Hofmeister series (KCl, NaCl, LiCl and ZnCl), we have shown that cellobiose solubilization is driven by the preferential accumulation of salts around the solutes which is stronger than cellobiose hydration. Yet contrary to the classical chaotropy hypothesis, increasing salt concentration leads to cellobiose dehydration in the presence of the strongest solubilizer ZnCl. However, thanks to cellobiose dehydration, cellobiose-salt interaction still remains preferential despite weakening salt accumulation. Based on such insights, the previous hypotheses based on hydrophobicity and polymer charging have also been evaluated quantitatively. Thus, our present study successfully paved a way towards identifying the basic driving forces for cellulose solubilization in a quantitative manner for the first time. When combined with unit additivity methods this quantitative information could lead to a full understanding of cellulose solubility.

RISM-Assisted Analysis of the Role of Alkali Metal Hydroxides in the Solvation of Cellulose in Alkali/urea Aqueous Solutions

“…The greater concentration close to cellulose implies a greater interaction between the corresponding metal ion and cellulose and a higher probability of making cellulose into a polyelectrolyte in the order Li + > Na + > K + . Hence, the data support the hypothesis of cellulose charging up (Nicol et al 2017), which claims that cellulose-ion interactions can make cellulose into a polyelectrolyte and cause its solvation (Bialik et al 2016).…”

“…The unit of is the volume per single solute molecule (Å 3 /molecule). indicates the accessibility of to the solute, which is correlated with the affinity of to the solute (Nicol et al 2017;Wernersson et al 2015). The KBI has been considered appropriate for describing all types of intermolecular interactions necessary for determining the thermodynamic properties of a solution.…”

RISM-assisted analysis of role of alkali metal hydroxides in the solvation of cellulose in alkali/urea aqueous solutions

“…The greater concentration close to cellulose implies a greater interaction between the corresponding metal ion and cellulose and a higher probability of making cellulose into a polyelectrolyte in the order Li + > Na + > K + . Hence, the 𝑁 𝑀𝑂𝐻 𝑒𝑥𝑐𝑒𝑠𝑠 data support the hypothesis of cellulose charging up (Nicol et al 2017), which claims that cellulose-ion interactions can make cellulose into a polyelectrolyte and cause its solvation (Bialik et al 2016).…”

“…The unit of 𝐺 𝛾 is the volume per single solute molecule (Å 3 /molecule). 𝐺 𝛾 indicates the accessibility of 𝛾 to the solute, which is correlated with the affinity of 𝛾 to the solute (Nicol et al 2017;Wernersson et al 2015). The KBI has been considered…”

Cellulose dissolution and regeneration using a non-aqueous, non-stoichiometric protic ionic liquid system

“…In order for cellulose molecules to remain in solution after disentanglement, they must be stabilised in solution. In cellobiose and other short chain cellulose molecules, the molecular interactions which provide this stabilisation consist of ''charging up'' caused by ion accumulation around the molecule in solution (Medronho and Lindman 2015;Bialik et al 2016;Nicol et al 2017). These molecular interactions could be present in cellulose.…”