Radical Grafting of Tetrafluoroethylene and Vinylidene Fluoride Telomers onto Silica Bearing Vinyl Groups

Radical addition of omega-iodofluorinated telomers was used to modify silica (S-50) nanoparticles bearing vinyl groups. These iodo terminated derivatives were either commercially available tetrafluoroethylene telomers, CnF2n+1I with n = 4 or 6, or vinylidene fluoride telomers, CnF2n+1 [VDF](m)I with m = 6 and 23. These latters were synthesized by radical telomerization of VDF with CnF2n+1I initiated by bis(4-tert-butylcyclohexyl) peroxydicarbonate in high yields (>85%). The resulting nanohybrids were characterized by solid state NMR spectroscopy, elemental analyses and thermogravimetry. A covalent grafting between double bonds and fluorinated iodotelomers was noted. The covering density of fluorinated chains was assessed and reported with respect to fluorinated chain lengths. These nanohybrids exhibited a high thermostability (higher than 400 degrees C under air), losing less than 10% by weight at 700 degrees C, and a low surface tension, gamma(s), from around 15 mN.m(-1) to about 44 mN.m(-1) for silica.