Regenerated cellulose membranes (RCMs) were p r e p a r e d f r o m c e l l u l o s e s u ffi c i e n t l y d i s s o l v e d i n [TMGH] 2 +[OOCOCH 2 CH 2 OCOO] 2− /DMSO (X ILS = 0.2, X ILs is the mole fraction of reversible ionic liquids in the mixed solvents) mixed solution under mild conditions (50 °C, 3 h, P CO 2 = 0.2 MPa) using different coagulation baths of ethanol, methanol, NaOH, and H 2 SO 4 aqueous solutions. The structure and properties of these membranes were characterized using various characteristic technologies. The membrane regenerated from ethanol exhibited good thermostability and mechanical, water vapor, and oxygen barrier properties with a tensile strength of 56.2 MPa, a tensile strain of 20.4%, an excellent water vapor permeability of 8.7 × 10 −3 g μm/m 2 day kPa, and an oxygen permeability (OP) of 4.087 cm 3 μm/m 2 day atm. The membranes regenerated from aqueous solutions of alkali and acid have an OP that tends to zero. This study provides a novel dissolving strategy to prepare cellulose membranes that have potential applications in the packaging, food, and agricultural industries.
Cellulose films are regarded as sustainable materials having wide applications in food packaging, separation, etc. Their preparation substantially relies on sufficient dissolution. Herein, various celluloses adequately dissolved in a new solvent system of carbon dioxide,1, 8-diazabicyclo [5.4.0] undec-7-ene and dimethyl sulfoxide (CO2/DBU/DMSO) were made in to films using different regeneration reagents. The films regenerated from ethanol and methanol presented homogeneous and smooth surfaces, while those from 5 wt % NaOH (aq.) and 5 wt % H2SO4 (aq.) showed rough surfaces, as analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The films regenerated from 5 wt % NaOH (aq.) and 5 wt % H2SO4 (aq.) rendered cellulose II structures, while those regenerated from alcohols had amorphous structures as evidenced using fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) results. The films made of microcrystalline cellulose had a good light transmittance of about 90% at 800 nm with a tensile strength of 55 MPa and an elongation break of 6.5%, while those from wood pulp cellulose demonstrated satisfactory flexibility with a tensile strength of 91 MPa and an elongation break of 9.0%. This research reports a simple, environmental, and sustainable method to prepare cellulose films of good mechanical properties.
Ionic liquids act as promoters for the dissolution of cellulose in GVL and also as catalysts for cellulose derivatization in GVL, providing a green and effective solvent system for cellulose processing and derivatization.
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