Multithiol-Functionalized Lignin as a Bio-Based Macromolecular Thiol for Thiol-ene Click Chemistry: Proof-of-Concept...

Area of Science:

• Macromolecular chemistry
• Polymer science
• Sustainable materials

Background:

• Lignin, a renewable biopolymer, offers potential for developing sustainable materials.
• Functionalization of lignin is key to unlocking its diverse applications.
• Thiol-ene chemistry provides a versatile platform for polymer modification.

Purpose of the Study:

• To develop a scalable synthesis of multithiol-lignin.
• To functionalize lignin with thiol groups for subsequent thiol-ene reactions.
• To create a cationic, quaternary-ammonium-lignin with enhanced properties for potential applications.

Main Methods:

• A two-step synthesis involving chloroacetylation of lignin followed by reaction with thiourea to introduce thiol groups.
• UV-initiated thiol-ene reaction between the synthesized multithiol-lignin and allylcholine chloride.
• Characterization using FTIR, NMR (1H, 13C, HSQC), SEM-EDS, EA, DLS, contact angle, and SFE analyses.

Main Results:

• Successful gram-scale synthesis of multithiol-lignin (DS ≈ 0.70).
• Formation of cationic, quaternary-ammonium-lignin (DS ≈ 0.80) via UV-mediated thiol-ene coupling.
• Demonstrated increase in hydrophilicity and significant UV blocking (≈100%) and antioxidant activity (≈75%) in functionalized lignin membranes.

Conclusions:

• A mild and efficient strategy for multithiol-lignin synthesis was established.
• The functionalized lignin exhibits tunable properties, including hydrophilicity and ionic character.
• The material shows potential for sustainable applications, particularly in food packaging.