Inserting -CHCH- into P(VDF-TrFE) by C-F activation mediated with Cu(0) in a controlled atom transfer radical elimination process

Chemical functionalization of poly(vinylidene fluoride) (PVDF) based fluoropolymers is an economic and convenient strategy to extend the application field of fluoropolymers. To enrich the functionalization tool box, in this contribution a controlled single electron transfer radical elimination (SET-RE) reaction has been successfully developed to introduce CHCH bonds into poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), which was synthesized through the full hydrogenation of poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)). In this SET-RE process, C-F bonds in TrFEs are directly activated by Cu(0) and 2,2'-bipyridine (Bpy) to generate CF₂-CH∗, followed by a controlled β-H elimination to complete the dehydrofluorination. The high selectivity of the elimination and the reaction mechanism could be well confirmed by the chemical composition of the resultant copolymers. The kinetics results show that the reaction rate is first-order with respect to the concentration of TrFE units and SET-RE is a finely controlled process. The reaction conditions, including the temperature, reaction time, dosage of Cu(0) and Bpy, concentration and even solvents, exhibit an influence on the reaction and the resultant copolymers. The introduction of CHCH leads to reduced crystallinity and an elevated ferro- to para-electric transition temperature of P(VDF-TrFE). This work offers a robust and controlled chemical tool to introduce reactive CHCH into the fluoropolymer for subsequent functionalization by directly activating C-F bonds.