Compressible Cellulose Wood Prepared with Deep Eutectic Solvents and Its Improved Technology

Abstract

Elastic materials have a wide range of applications in many industries, but their widespread use is often limited by small-scale production methods and the use of highly polluting chemical reagents. In this study, we drew inspiration from research on wood softening to develop an environmentally friendly and scalable approach for producing a new type of compressible wood material called CW from natural wood. To achieve this, we employed a top-down approach using a novel type of “ionic liquid” eutectic solvent (DES) that is cost-effective, environmentally friendly, and recyclable. After treatment with DES, the resulting CW demonstrated good elasticity and durable compressibility, which was achieved by removing some lignin and hemicellulose from the wood and thinning the cell walls, thereby creating a honeycomb structure that allows for sustained compression and rebound. However, we found that the wood treated with a single eutectic solvent showed some softening (CW-1), although there was still room for further improvement of its elasticity. To address this, we used a secondary treatment with sodium hydroxide alkali solution to produce a softer and more elastic wood (CW-2). We conducted a series of comparative analyses and performance tests on natural wood (NW) and CW, including microscopic imaging; determination of chemical composition, mechanical properties, and compressive stress effects; and laser confocal testing. The results show that the DES and sodium hydroxide alkali solution treatments effectively removed some lignin, hemicellulose, and cellulose from the wood, resulting in the thinning of the cell walls and creating a more elastic material with a sustainable compression rebound rate of over 90%. The various properties of CW, including its elasticity, durability, and sustainability, provide great potential for its application in a range of fields, such as sensors, water purification, and directional tissue engineering.