Abstract
Chemical reaction between silanol-modified wood and methyltrimethoxysilane (MTMS) was carried out using two different approaches with dibutyltin dilaurate (DBTDL) or ethylamine (EtNH2) as catalysts. Modifications were characterised by Fourier-transform infrared (FTIR) spectroscopy, as well as solid-state 13C and 29Si cross-polarisation with magic-angle spinning nuclear magnetic resonance (CP-MAS NMR) spectroscopy and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis. Silanol-modified wood was obtained by carbamoylation reaction with 3-isocyanatopropyltriethoxysilane (IPTES) and subsequent hydrolysis of the triethoxysilane end groups. 29Si CP-MAS NMR spectroscopy indicated that SiOH groups existed mostly in the form of mono- and di-condensed structures in wood, whatever the level of modification (low or high). The attachment of methyltrimethoxysilane (MTMS) molecules to silanol sites was apparently achieved when ethylamine was used as a catalyst. The reacted MTMS remaining in wood was found to exist mostly in the form of polysiloxane polymers (or oligomers), as shown by 29Si CP-MAS NMR results. Reactions performed with unmodified wood were much less effective, thereby demonstrating the importance of the IPTES pre-treatment.
References
Blitz, J.P., Shreedhara Murthy, R.S., Leyden, D.E. (1987) Ammonia-catalyzed silylation reactions of Cab-O-Sil with methoxymethylsilanes. J. Am. Chem. Soc.109:7141–7145.10.1021/ja00257a039Search in Google Scholar
Bogart, G., Leyden, D.E. (1994) Investigation of amine-catalysed alkoxysilane-modified Cab-O-Sil by drift spectroscopy. J. Colloid Interface Sci.167:18–26.10.1006/jcis.1994.1329Search in Google Scholar
Crandall, J.K., Morel-Fourrier, C. (1995) Siloxanes from the hydrolysis of isopropyltrimethoxysilane. J. Organomet. Chem.489:5–13.10.1016/0022-328X(94)05159-9Search in Google Scholar
Hill, C.A.S., Farahani, M.R.M., Hale, M.D.C. (2004) The use of organo alkoxysilane coupling agents for wood preservation. Holzforschung58:316–325.10.1515/HF.2004.049Search in Google Scholar
Hjertberg, T., Palmlöf, M., Sultan, B.-A. (1991) Chemical reactions in crosslinking of copolymers of ethylene and vinyltrimethoxy silane. J. Appl. Polym. Sci.42:1185–1192.10.1002/app.1991.070420503Search in Google Scholar
Jesionowski, T., Zurawska, J., Krysztafkiewicz, A., Pokora, M., Waszak, D., Tylus, W. (2003) Physicochemical and morphological properties of hydrated silicas precipitated following alkoxysilane surface modification. Appl. Surf. Sci.205:212–224.10.1016/S0169-4332(02)01090-5Search in Google Scholar
Mai, C., Militz, H. (2004) Modification of wood with silicon compounds. Inorganic silicon compounds and sol-gel systems: a review. Wood Sci. Technol.37:339–348.Search in Google Scholar
Sèbe, G., Brook, M.A. (2001). Hydrophobization of wood surfaces: covalent grafting of silicone polymers. Wood Sci. Technol.35:269–282.Search in Google Scholar
Sèbe, G., De Jéso, B. (2000) The dimensional stabilisation of maritime pine sapwood (Pinus pinaster) by chemical reaction with organosilicon compounds. Holzforschung54:474–480.10.1515/HF.2000.080Search in Google Scholar
Sèbe, G., Tingaut, P., Safou-Tchiama, R, Pétraud, M., Grelier, S., De Jéso, B. (2004) Chemical reaction of maritime pine sapwood (Pinus pinaster Soland) with alkoxysilane molecules: a study of chemical pathways. Holzforschung58:511–518.10.1515/HF.2004.078Search in Google Scholar
Tingaut, P., Weigenand, O., Militz, H., De Jéso, B., Sèbe, G. (2005) Functionalisation of wood by reaction with 3-isocyanatopropyltriethoxysilane: grafting and hydrolysis of the triethoxysilane end groups. Holzforschung59:397–404.10.1515/HF.2005.065Search in Google Scholar
Tissot, I., Reymond, J.P., Lebfevre, F. Bourgeat-Lami, E. (2002) SiOH-functionalized polystyrene latexes. A step toward the synthesis of hollow silica nanoparticles. Chem. Mater.14:1325–1331.Search in Google Scholar
White, L.D., Tripp, C.P. (2000) An infrared study of the amine-catalyzed reaction of methoxymethylsilanes with silica. J. Colloid Interface Sci.227:237–243.10.1006/jcis.2000.6895Search in Google Scholar PubMed
Yoshida, W., Castro, R.P., Jou, J.-D., Cohen, Y. (2001) Multilayer alkoxysilane silylation of oxide surfaces. Langmuir17:5882–5888.10.1021/la001780sSearch in Google Scholar
©2006 by Walter de Gruyter Berlin New York