Preparation of PVDF-grafted-PS involving nitroxides

A novel route to prepare fluorinated grafted copolymers via the use of nitroxides and under mild conditions is described. First, iodine transfer polymerization of vinylidene fluoride (VDF) in the presence of 1-iodoper-fluorohexane led to two PVDFs (average molar masses of 1700 and 4000 g mol(-1) and dispersities of 1.2). Then, the grafting of nitroxide moieties onto PVDF backbone was achieved in solution without any polymer activation. The obtained PVDF-g-nitroxide polymers acted as efficient macroinitiators for the polymerization of styrene leading to PVDF-g-PS graft copolymers with styrene content ranging from 17 to 40 w.% and PS molar masses varying from 1000 to 1500 g mol(-1). It was experimentally evidenced that the grafting took place from methylenic protons, especially from tail-to-tail addition, and theoretical calculations of bond dissociation energies confirmed such a finding. It was also demonstrated that the nature of the solvent had a great influence on the success of the grafting mechanism as the reaction was only efficient in N-methyl pyrrolidone. Considering the high chemical stability of PVDF, this chemical route paves the way towards the synthesis of various valuable graft copolymers.