Grafting of cellulose by fluorine-bearing silane coupling agents

The surface of model cellulose fibres, Avicell (AV), as well as that of Whatman paper (WP) was chemically modified with two fluorine-bearing alkoxysilane coupling agents, namely: 3,3,3-trifluoropropyl trimethoxysilane (TFPS) and 1H,1H,2H,2H,perfluorooctyl trimethoxysilane (PFOS). The occurrence of the grafting of soxhlet extracted modified cellulose was confirmed by the presence of silicon and fluorine atoms detected by elemental analysis, X-ray photoelectron spectroscopy and Electron Dispersion Energy/Scanning Electron Microscopy (EDS/SEM). The contact angle measurements showed that, after grafting, the surface of AV and WP samples became totally highly hydrophobic with a contact angle of 140°. Thus, the polar contribution to the surface energy of the modified substrates was found to be close to zero. These modified substrate could be interesting for application such as self-cleaning surface, wipes paper, grease barrier paper or for biocomposite with a polar matrix.