Preparation of Cellulose Films from Sustainable CO2/DBU/DMSO System

Wood cellulose films with different foldabilities triggered by dissolution and regeneration from concentrated H2SO4 and NaOH/urea aqueous solutions

Forests are a major source of wealth for Canadians, and cellulose makes up the "skeleton" of wood fibers. Concentrated H2SO4 and NaOH/urea aqueous solutions are two efficient solvents that can rapidly dissolve cellulose. Our preliminary experiment obtained regenerated wood cellulose films with different mechanical properties from these two solvents. Therefore, herein, we aim to investigate the effects of aqueous solvents on the structure and properties of wood cellulose films. Regenerated cellulose (RC) films were produced by dissolving wood cellulose in either 64 wt% H2SO4 solution (RC-H4) or NaOH/urea aqueous solution (RC-N4). RC-H4 showed the higher tensile strength (109.78 ± 2.14 MPa), better folding endurance (20-28 times), and higher torsion angle (42°) than RC-N4 (62.90 ± 2.27 MPa, un-foldable, and 12°). The increased cellulose contents in the H2SO4 solutions from 3 to 5 wt% resulted in an improved tensile strength from 102.61 ± 1.99 to 132.93 ± 5.64 MPa and did not affect the foldability. RC-H4 also exhibited better water vapor barrier property (1.52 ± 0.04 × 10-7 g m-1 h-1 Pa-1), superior transparency (~90 % transmittance at 800 nm), but lower thermal stability compared to RC-N4. This work provides special insights into the regenerated wood cellulose from two aqueous solvents and is expected to facilitate the development of high-performance RC films from abundant forestry resources.

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.

Dual modification of cellulose with esterification and carbonation in DMSO/DBU/CO2 system as fluorescent additive for pH detection

An easy and effective way to synthesize dual-functionalized cellulose derivatives with processability and fluorescence functionality by one-pot modification of successive esterification and carbonation under mild condition is established with the use of DMSO/DBU/CO₂ system. Accordingly, four kinds of dual-functionalized cellulose derivatives with rather good fluorescent response are obtained. After blending the synthesized dual-functionalized cellulose derivative with cellulose acetate as functional additive in solution, cast film with the elastic modulus, stress and strain reaches to 2.2 GPa, 34.1 MPa and 5.7% is prepared. Besides, the cast film also exhibits the ability to detect the pH value at 12-14 with detection accuracy of 0.4 through the change of fluorescent color. This research shows a simple but effective way to prepare dual-functionalized cellulose derivatives for the high-quality applications in field of detection.

Irregular solution thermodynamics of wood pulp in the superbase ionic liquid [m-TBDH][AcO]

Knowledge of solution thermodynamics is fundamental for solution control and solvent selection processes. Herein, experimentally determined thermodynamic quantities for solutions of wood pulp (hardwood dissolving pulp, i.e. cellulose) in [m-TBDH][AcO] are presented. Model-free activities (a_i,j) and associated mass fraction (w_i,j) activity coefficients (Ω_i,j), are determined to quantify inherent solution non-ideality. Access to the Gibbs energy of mixing, G_mix, in combination with associated partial molar thermodynamic quantities, reveal strong enthalpically favourable (exothermic) interactions due to solvent-j and solute-i contact-encounters. Onset of an entropy driven phase instability appears at increased temperatures as excess entropic contributions dominate solvation character of the irregular solutions formed.

Thermochemical analysis of cellulose dissolution character in the superbase containing protic ionic liquid [m-TBDH][AcO] reveals lower critical solution temperature (LCST) behaviour.