“Grafting From” Polymerization of Vinylidene Fluoride (VDF) from Silica to Achieve Original Silica–PVDF Core–Shells

Abstract

A new method of surface modification based on the “grafting from” polymerization process enabled to prepare original silica nanoparticles covered with PDVF “hair”. This strategy involved two steps: (i) the radical addition of 1,4-diiodoperfluorobutane initiated by tert -butylperoxypivalate onto the double bonds of silica nanoparticles (specific area of 150 m 2 g –1 ) led to silica that bore C 4 F 8 I end-groups on its surface, and (ii) its use as original macrochain transfer agent in the “grafting from” polymerization of vinylidene fluoride (VDF) initiated by bis(4- tert -butylcyclohexyl) peroxydicarbonate. The characterizations of both modified silica were achieved by elemental analysis, 1 H and 19 F magic angle spinning solid state rotational-echo double resonance NMR spectroscopy, thermogravimetry, and water contact angle (WCA) assessments. The grafting efficiency was confirmed by three features: (i) the increase of weight percentage of fluorine atom (that ranged from 0 for the starting unsaturated silica to 2.50% for silica-bearing −C 4 F 8 I end-group and to 3.32% for original silica–PVDF core–shells), (ii) a high thermostability (that reached more than 400 °C under air), and (iii) a good hydrophobicity: the WCA values were ranging from 84° to 109° and to 126° for vinyl silica, for silica coated with −C 4 F 8 I, and for PVDF-covered silica nanoparticles, respectively.