Efficient Cellulose Dissolution and Film Formation Enabled by Superbase Amino Acid Ionic Liquids

Abstract

Cellulose is a promising feedstock for the production of sustainable materials. To fully utilize its potential, exploring efficient cellulose solvents is a paramount prerequisite. In this study, ten superbase amino acid ionic liquids (SAAILs) are synthesized using 1,5‐diazabicyclo[4.3.0]non‐5‐ene (DBN) and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) with different amino acid anions via a simple neutralization method. The properties of these SAAILs, such as viscosity and glass transition temperature, varied with their cation and anion structures. The ability of the SAAILs to dissolve cellulose is related to their Kamlet–Taft parameters, particularly hydrogen bond basicity (β). The main driving force for cellulose dissolution in SAAILs is thought to be hydrogen bonding interactions between SAAILs and cellulose hydroxyl groups. Four SAAILs composed of DBN or DBU cations and proline, or aspartic acid anions are identified as promising solvents for preparing regenerated cellulose films (RCFs). The RCF prepared from [DBN]Proline(Pro) showed a favorable combination of high tensile strength (76.9 MPa), high Young's modulus (5201.2 MPa), good transparency (≈70% at 550 nm), and smooth surface morphology. These halogen‐ and metal‐free SAAILs show the potential to provide a new avenue for cellulose processing.

Novel diacid–superbase ionic liquids for efficient dissolution of cellulose and simultaneous preparation of multifunctional cellulose materials

“…35 The crystallinity (CrI) of cellulose was calculated by referring to the published work. 72 The CrI values of cellulose films with different concentrations (2 wt%, 4 wt%, 6 wt%, and 8 wt%) were 55.3%, 54.9%, 55.5%, and 55.9%, which were less than the CrI of MCC (83.8%). The above results indicated that during the dissolution of cellulose, intermolecular and intramolecular hydrogen bonds were disrupted, resulting in the destruction of the original cellulose I structure and the cellulose aggregate into the form of a single molecular chain.…”