Soft-Segment Containing Lignin-Based Polyhydroxyurethanes: Controllable Flexibility Through PDMS Integration.

Area of Science:

• Polymer Chemistry
• Materials Science
• Biomass Valorization

Background:

• Lignin, a renewable aromatic polymer, offers rigidity but lacks flexibility.
• Copolymerization with poly(dimethylsiloxane) (PDMS-NH₂) can enhance lignin's elasticity.
• Developing adaptable lignin-based materials is crucial for sustainable applications.

Purpose of the Study:

• To synthesize and characterize novel lignin-based polyhydroxyurethane copolymers (CCL-PDMS-PHUs).
• To investigate the effect of PDMS-NH₂ content on the mechanical and thermal properties of the copolymers.
• To demonstrate the potential of these materials for applications requiring tailored properties.

Main Methods:

• Lignin modification to cyclic carbonate-functionalized lignin (CCL) using CO₂.
• Copolymerization of CCL with bis(3-aminopropyl)-terminated poly(dimethylsiloxane) (PDMS-NH₂) via ring-opening.
• Structural confirmation using FT-IR, ¹³C NMR, and ¹H NMR spectroscopy.
• Thermal analysis (TGA, DSC) to determine decomposition and glass transition temperatures.
• Mechanical testing to evaluate stiffness and flexibility.

Main Results:

• Successful synthesis of CCL-PDMS-PHU copolymers confirmed by spectroscopic analysis (urethane bond formation).
• Tunable thermal stability with 5% decomposition temperatures between 246-265 °C and Tg from 44-66 °C.
• Adjustable mechanical properties observed, with higher PDMS-NH₂ content increasing softness and lower content increasing stiffness.
• Demonstrated control over material properties by varying PDMS-NH₂ composition.

Conclusions:

• CCL-PDMS-PHUs exhibit tunable mechanical and thermal characteristics.
• The incorporation of PDMS-NH₂ effectively modifies lignin's inherent stiffness.
• These novel copolymers represent promising, adaptable materials for diverse applications demanding specific performance profiles.