Lignin Polyurethane Aerogels: Influence of Solvent on Textural Properties

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Materials

Background:

• Lignin, a natural polymer, offers potential as a sustainable alternative to petroleum-based polyols.
• Polyurethane aerogels possess desirable properties like high surface area and mechanical stability.
• Developing methods to utilize native lignin in advanced materials is crucial for sustainability.

Purpose of the Study:

• To investigate the use of native lignin as a biopolyol for synthesizing polyurethane aerogels.
• To explore the influence of different lignin types and solvent systems on aerogel microstructure and properties.
• To demonstrate a tunable approach for creating lignin-based polyurethane aerogels with controlled characteristics.

Main Methods:

• Evaluation of Organosolv, Aquasolv, and Soda lignin based on structural characteristics.
• Synthesis of lignin polyurethane aerogels using various solvents (DMSO, pyridine, acetone) and their mixtures.
• Characterization of aerogel microstructure, density, specific surface area, and mechanical stability.

Main Results:

• Organosolv lignin was identified as the optimal type for polyurethane aerogel synthesis.
• Solvent affinity significantly influenced microstructure: high affinity led to dense materials, low affinity to macroporous structures.
• Mixed solvent systems (e.g., 75% DMSO/acetone) enabled control over phase separation, yielding homogeneous, mesoporous aerogels.
• A 75% DMSO/acetone mixture produced mechanically stable aerogels with low density (0.49 g cm⁻³) and high surface area (~300 m² g⁻¹).

Conclusions:

• Native lignin can be effectively used as a biopolyol for sustainable polyurethane aerogel production.
• Solvent composition is a critical factor in controlling the microstructure and properties of lignin-based aerogels.
• This study presents a versatile method for tailoring lignin polyurethane aerogels for various applications.