Abstract
The synthesis of CnF2n+1(VDF)x-(CH2)p- where n = 2, 4; x = 2, 3, 4; p = 0, 1, 2 and VDF and stand for vinylidene fluoride (VDF) and I, OH, or CO2H, respectively, are presented. First, the radical telomerization of VDF with CnF2n+1-I to direct low molecular weight-telomers was investigated in various experimental conditions: initiators, temperatures and solvents to favour the formation of CnF2n+1(VDF)xI. Whatever the experimental conditions, it was observed the regioselective radical addition of CnF2n+1 radical onto the methylene site of VDF. Then, ethylenation of these VDF telomers was achieved in the presence of peroxy initiator with a quantitative conversion of the VDF-containing iodide reactants. Chemical change of RF(VDF)xC2H4I into RF(VDF)C2H4OH occurred in two steps: (i) from a mixture of DMF/water (for which a 6/1 content led to the best conditions); (ii) followed by a basic medium to saponify RF(VDF)xCH2CH2OCOH formiate into the corresponding VDF-containing alcohols. Suitable conditions were found to avoid any dehydrofluorination of the VDF telomeric chain. Oxidation of these fluorinated alcohols in the presence of H2SO4/CrO3 mixture led to the corresponding CnF2n+1(VDF)xCH2CO2H carboxylic acids. Surface tensions of these VDF-containing carboxylic acids were achieved reaching a value of 19.8 mN m-1 for a surfactant concentration of 5 g L-1, showing similar values as that of commercially available perfluorooctanoic acid (PFOA) while critical micellar concentration value of C2F5CH2CF2CH2CF2CH2CO2H was 1.4 g L-1 at room temperature.