Surfactant-assisted fabrication of ultra-permeable cellulose gels with macro channels and insights on regeneration of cellulose from ionic liquids

Abstract

This work presents a new method to fabricate cellulose gels with micrometer size channels that offer ultra-permeability. A non-ionic surfactant was key to the formation of the macro channels. We studied the chemical microstructure of the [Bmim]Cl (1‑butyl‑3‑methylimmidozolium chloride)-cellulose-surfactant mixtures by Fourier transform infrared spectroscopy (FTIR) imaging system. We then questioned the soft template theory and confirmed our surfactant-induced and diffusion-driven hypothesis to explain the formation of the macro channels. We also found that the microstructure of the gels was impacted by the surfactant, according to nitrogen physisorption, X-ray diffraction, nuclear magnetic resonance, and scanning electron microscopy results. Time-dependent attenuated total reflection-FTIR (ATR-FTIR) was used to monitor the phase separation of the ionic liquid and cellulose in situ during the sol-gel transition. A two-step model of cellulose regeneration was thus proposed. Our study offers a strategy to fabricate hierarchical porous materials with macro channels and can increase the understanding of cellulose regeneration mechanism from ionic liquids.