Organocatalytic Cellulose Dissolution and In Situ Grafting of ϵ-Caprolactone via ROP in a Reversible DBU/DMSO/CO2 System

Recent Advances in Cellulose-Based Hydrogels Prepared by Ionic Liquid-Based Processes

This review summarizes the recent advances in preparing cellulose hydrogels via ionic liquid-based processes and the applications of regenerated cellulose hydrogels/iongels in electrochemical materials, separation membranes, and 3D printing bioinks. Cellulose is the most abundant natural polymer, which has attracted great attention due to the demand for eco-friendly and sustainable materials. The sustainability of cellulose products also depends on the selection of the dissolution solvent. The current state of knowledge in cellulose preparation, performed by directly dissolving in ionic liquids and then regenerating in antisolvents, as described in this review, provides innovative ideas from the new findings presented in recent research papers and with the perspective of the current challenges.

Sustainable One-Pot Cellulose Dissolution and Derivatization via a Tandem Reaction in the DMSO/DBU/CO2 Switchable Solvent System

New sustainable concepts have to be developed to overcome the increasing problems of resource availability. Cellulose derivatives with tunable material properties are promising biobased alternatives to existing petroleum-derived polymeric materials. However, the chemical modification of cellulose is very challenging, often requiring harsh conditions and complex solubilization or activation steps. More sustainable procedures toward novel cellulose derivatives are therefore of great interest. Herein, we describe a novel concept combining two approaches, (i) tandem catalysis and (ii) cellulose derivatization, by applying a single catalyst for three transformations in the DMSO/DBU/CO₂ switchable solvent system. Cellulose was functionalized with four different biobased isothiocyanates, which were formed in situ via a catalytic sulfurization of isocyanides with elemental sulfur, preventing the exposure and handling of the isothiocyanates. The degree of substitution of the formed O-cellulose thiocarbamates was shown to be controllable in a range of 0.52-2.16 by varying the equivalents of the reactants. All obtained products were analyzed by ATR-IR, ¹H, ¹³C, and ³¹P NMR spectroscopy as well as size exclusion chromatography, elemental analysis, differential scanning calorimetry, and thermal gravimetric analysis. Finally, the tandem reaction approach was shown to be beneficial in terms of efficiency as well as sustainability compared to a stepwise synthesis. Recycling ratios ranging from 79.1% to 95.6% were obtained for the employed components, resulting in an E-factor of 2.95 for the overall process.