Synthesis and Characterization of Poly(vinylidene fluoride)-g-poly(styrene) Graft Polymers Obtained by Atom Transfer Radical Polymerization of Styrene

Poly(vinylidene fluoride)-g-poly(styrene) graft copolymers (PVDF-g-PS) were synthesized by the "grafting from" method from a PVDF macroinitiator bearing bromine side groups. This fluorinated macroinitiator was obtained from the radical copolymerization of VDF with 8-bromo-1H,1H,2H-perfluorooct-1-ene (BDFO), and then it was used in the atom transfer radical polymerization (ATRP) of styrene initiated by CuIBr/1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) catalyst. First, the synthesis of a model poly(styrene) was investigated starting from 1-bromoperfluorooctane (C8F17Br) as the initiator to check the reactivity of −CF2−Br in ATRP process. Successful ATRP of styrene in the presence of 1-bromoperfluorooctane was observed from a kinetic study and NMR spectroscopy, and the activation rate constant of this initiator (kact = 35 × 10-3 M-1 s-1 at 35 °C in acetonitrile) was assessed for the first time. In a second part, ATRP of styrene was also studied from poly(VDF-co-BDFO) copolymers as the macroinitiators, taking into account: (i) the effect of the polymerization temperature, (ii) the ligand concentration in the ATRP catalyst, and (iii) the amount of solvent vs the conversion of poly(styrene). The formation of graft copolymers was confirmed by size exclusion chromatography and by 1H and 19F NMR spectroscopies. Interestingly, the linear dependences of both the evolutions of ln([M]0/[M]) vs time and of the molecular weights of the resulting graft copolymers vs the styrene conversions, and the decrease of their dispersity indexes vs the styrene conversions evidenced the controlled behavior of that graft polymerization.