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

Area of Science:

• Materials Science
• Green Chemistry

Background:

• Cellulose is a sustainable feedstock for advanced materials.
• Efficient cellulose solvents are crucial for unlocking its potential.
• Superbase amino acid ionic liquids (SAAILs) offer a potential solution.

Purpose of the Study:

• To synthesize and characterize novel superbase amino acid ionic liquids (SAAILs).
• To investigate the cellulose dissolution capabilities of SAAILs.
• To explore the potential of SAAILs for producing high-quality regenerated cellulose films (RCFs).

Main Methods:

• Synthesis of ten SAAILs using 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with various amino acid anions.
• Characterization of SAAIL properties (viscosity, glass transition temperature) and correlation with Kamlet-Taft parameters (hydrogen bond basicity).
• Preparation and characterization of regenerated cellulose films (RCFs) using promising SAAILs.

Main Results:

• SAIL properties varied based on cation and anion structure.
• Cellulose dissolution correlated with SAAIL hydrogen bond basicity.
• Four SAAILs (DBN/DBU with proline or aspartic acid) effectively dissolved cellulose.
• RCF from [DBN]Proline exhibited high tensile strength (76.9 MPa), Young's modulus (5201.2 MPa), good transparency (~70%), and smooth morphology.

Conclusions:

• Hydrogen bonding is the primary mechanism for cellulose dissolution in SAAILs.
• Halogen- and metal-free SAAILs are effective and sustainable solvents for cellulose processing.
• The developed SAAILs provide a new pathway for producing advanced regenerated cellulose materials.