Morphology-Controlled Syringaldehyde Microemulsions Achieve Deep Wood Penetration and Enhance Multi-Functional Durability via Silane Cross-Linking

Developing green multifunctional wood protection systems is a critical strategy for prolonging the service life of wood under fungal attack and humid environmental conditions. In this study, a morphology-tunable aqueous microemulsion of syringaldehyde (SA) was constructed using sodium dodecyl sulfate (SDS) as the surfactant, benzyl alcohol (BA) as the cosurfactant, enabling efficient dispersion and delivery of this biobased antifungal agent. By adjusting the SDS/SA ratio, micelles with tunable particle sizes and morphologies were obtained, and their penetration degree with poplar wood was systematically investigated. All-atom molecular dynamics (MD) revealed a spontaneous micellization pathway in an aqueous environment. Spherical micelles formed at SDS/SA = 1 exhibited the highest colloidal stability, efficient transport through wood vessels and pit membranes, and the lowest interfacial tension, thereby achieving the deepest penetration and uniform distribution of SA within the wood matrix. To enhance fixation and durability of SA, (3-aminopropyl) triethoxysilane (APTES) was introduced as a post-treatment agent to chemically anchor SA via the formation of Si–O–C and C═N covalent bonds. The resulting SA-APTES-modified wood demonstrated excellent comprehensive performance, including superior antifungal performance (mass loss <5.14%), reduced leachability (SA leaching rate <15.2%), improved dimensional stability (antishrink efficiency, ASE >40% at 65% relative humidity), enhanced hydrophobicity (water contact angle >120°), and outstanding UV aging resistance. Furthermore, life cycle assessment (LCA) and techno-economic analysis (TEA) indicated that this green protection system had a lower environmental impact and a lower minimum selling price compared to conventional preservatives. This research provides a sustainable and structure–function guided approach for the development of high-performance biobased wood protection systems.