Grafting polymers in the wood structure: towards functional lignocellulosic materials
May 10-15, 2015
Wood is a rather exceptional material that has been used for thousands of years, and it represents an immense reservoir of natural polymers. When wood is felled, the material loses some of its natural properties upon drying, and is more exposed to damages caused by external conditions, such as moisture cycles, UV-light, or biodegradation. Several modification techniques were developed to protect wood against external aggressions.1,2 Inherently, such treatments were designed to make essentially inert wood materials, which drastically limit post-functionalization possibilities and alternative utilizations. We believe that wood, as a large scale self-assembled material with a complex hierarchical architecture, could be much better utilized if limitations in material functionalization could be overcome. The goal of our research is therefore to show that chemical modification can be used not only to obtain a more durable and reliable material, but also to bring new functionalities into wood. We implemented grafting polymerization techniques in/at the complex and heterogeneous macromolecular assembly of wood cell walls that allow for the introduction of novel functionalities in wood-based materials while retaining the hierarchical multi-scale framework for modular polymerization processes. Specifically, we transferred various well-known polymerization techniques - such as free radical polymerization (FRP),3,4 ring-opening polymerization (ROP),5 and atom transfer radical polymerization (ATRP) - to a rather unusual substrate material. Using these techniques, synthetic polymer chains were covalently attached to wood fibers. The versatility and potential of the approaches are twofold: by using various graft polymerization techniques, we have access to different monomers and we can control the final distribution of the polymer in the wood structure. We believe that such functionalized wood materials with advanced property profiles will be used to produce wood-based materials for a variety of applications in the future.
 Hill, C. A. S. Wood Modification: Chemical, Thermal and Other Processes; Wiley: New York, 2006.  Rowell, R. M. Handbook of Wood Chemistry and Wood Composites; 2nd ed.; CRC Press: Boca Raton, 2012.  Cabane, E.; Keplinger, T.; Merk, V.; Hass, P.; Burgert, I. ChemSusChem 2014, 7, 1020-1025.  Keplinger, T.; Cabane, E.; Chanana, M.; Hass, P.; Merk, V.; Gierlinger, N.; Burgert, I. Acta Biomaterialia 2015, 11, 256-263.  Ermeydan, M. A.; Cabane, E.; Hass, P.; Koetz, J.; Burgert, I. Green Chemistry 2014, 16, 3313-3321.