Stable Robust Lignin/Silver-Based Superhydrophobic Coatings with Long-Term Antibacterial Properties through Hydrothermal Treatment

Wood and other biomass materials are of poor dimensional stability and susceptible to harmful bacteria infestation, but it is difficult to construct a robust and antibacterial superhydrophobic coating on their surface. For that, alkaline lignin (AL)/Ag composite particle by hydrothermal treatment was employed as the rough structure and antibacterial agent, hexadecyltrimethoxysilane and methyltrimethoxysilane as the low surface free energy modifiers, and polydimethylsiloxane as the binding agent to get the superhydrophobic coating with excellent robustness and antibacterial properties through simple mixing and spraying onto wood surface. In the system, AL/Ag composite particles were formed by situ recombination of Ag+ under redox reacted with the phenolic hydroxyl group of AL. Through hydrothermal treatment, the intermolecular and intramolecular forces of lignin were enhanced, making hydrothermal AL/Ag (H-AL/Ag) composite particles have good hardness and protection for antibacterial agents. The prepared coating exhibits excellent superhydrophobicity (WCA of 165 degrees and SA of 3 degrees), outstanding antibacterial properties (99.9% inhibition against Escherichia coli and Staphylococcus aureus), remarkable abrasion resistance (maintain superhydrophobic after 62 abrasion cycles), and ultraviolet (UV) resistance (withstand 13 h under 500 W of UV irradiation without losing superhydrophobicity), showcasing distinguished potential in wood protection.