Crystallinity of regenerated cellulose from [Bmim]Cl dependent on the hydrogen bond acidity/basicity of anti-solvents

Abstract

Cellulose, regarded as a potential sustainable resource for the future, can dissolve and regenerate in ionic liquids (ILs) upon adding anti-solvents. Improving the regeneration conditions, like changing the antisolvents, could optimize the properties of regenerated cellulose-based materials. Previous studies pointed out that the diffusion processes of anti-solvents plays a significant role in the determination of the properties of regenerated cellulose fibers/films. However, the cellulose regeneration mechanism from ILs has not been clarified. Here, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was introduced to monitor the molecular diffusion processes of four anti-solvents in situ.The crystallinity of regenerated cellulose showed a negative correlation with respect to the diffusion coefficient. In addition, the interaction of imidazolium cations and anti-solvent molecules was evaluated from the peak shifting during the diffusion processes. Furthermore, Taft and Kamlet scales were used to quantify the interaction between IL cations/anions and anti-solvent molecules, eliciting distinct cellulose regeneration paths in different anti-solvents.

Study on ionic liquid/cellulose/coagulator phase diagram and its application in green spinning process

“…A larger blue shift of the C\ \O stretching peak was acquired in water than that in ethanol, indicating that water has a stronger interaction with the solvent than ethanol. Therefore, the observations from this work and Fan et al [37] agree with each other. In addition, as indicated by Fan et al [37], water acted mostly as an H-bond donor, making anions being solvated more intensively, and the interaction between IL ions and cellulose hydroxyl groups was broken in a relatively sharp path in water.…”

“…Therefore, the observations from this work and Fan et al [37] agree with each other. In addition, as indicated by Fan et al [37], water acted mostly as an H-bond donor, making anions being solvated more intensively, and the interaction between IL ions and cellulose hydroxyl groups was broken in a relatively sharp path in water. In contrast, ethanol interacts with the imidazolium-cations more intensively, and the interaction between cellulose and anion/imidazoliumcations was broken mostly by solvation, which is a slow path.…”

“…This observation is consistent with the experimental results determined directly with the cloud point measurement. Fan et al [37] also studied the effect of coagulator on the ternary system of [BMIM]Cl/cellulose/coagulator with the in-situ ATR-FTIR. A larger blue shift of the C\ \O stretching peak was acquired in water than that in ethanol, indicating that water has a stronger interaction with the solvent than ethanol.…”

Advances in the use of microgels as emulsion stabilisers and as a strategy for cellulose functionalisation

“…As discussed previously (''Top-Down Approaches'' section), like other polymer microgels the nature and morphology is highly dependent on the properties of the macrogel, which in turn is affected by the amount of cellulose dissolved and the method and conditions of coagulation (applied shear force, temperature, anti-solvent, etc.) (Li et al 2009;Fan et al 2017;Rajeev and Basavaraj 2019).…”

Impact of non‐solvent on regeneration of cellulose dissolved in 1‐(carboxymethyl)pyridinium chloride ionic liquid

“…Geng and Henderson argued that cellulose dissolved using 1‐ethyl‐3‐methylimidazolium acetate can be regenerated with various morphologies and crystallinities using a variety of non‐solvents. The great contribution of regeneration conditions in the optimization of the properties of regenerated cellulose was demonstrated by Fan et al …”