Iodine Transfer Copolymerization of Vinylidene Fluoride and a-Trifluoromethacrylic Acid in Emulsion Process Without Any Surfactants
Résumé
The synthesis of poly(VDF-co-TFMA) copolymers (where VDF and TFMA stand for vinylidene fluoride and a-trifluoromethacrylic acid, respectively) by iodine transfer polymerization without any surfactant is presented. First, the synthesis and the control of the copolymerization of VDF and TFMA were investigated in the presence of two chain transfer agents, 1-perfluorohexhyl iodide (C6F13I) and 1,4-diodoperfluorobuane (IC4F8I). TFMA monomer was incorporated in the copolymer in good yields. Moreover, the molecular weights of the resulting poly(VDF-co-TFMA) copolymers were in good agreement with the theoretical values for feed of TFMA/VDF ratios that ranged from 50/50 to 0/100 mol %, showing that TFMA does not disturb the controlled radical polymerization of VDF. The microstructures of the produced copolymers were characterized by 1H and 19F NMR to assess the amount of each comonomer, and the molecular weights and the end-groups of the copolymers. The results on the control of the copolymerization were compared to those obtained with and without the presences of TFMA and surfactant. The addition of a low amount of TFMA improved the control of the polymerization of VDF without using any surfactant. Also, the size of particles, assessed by light scattering, was smaller than 200 nm. The addition of TFMA in low proportions, that is, 5 to 10 mol %, enabled us to stabilize the particle size and to decrease the size by one order of magnitude. The emulsifying behavior of TFMA (in low amount in the copolymer, that is, \10 mol %) was similar to those achieved when a surfactant was added. Indeed, neither sedimentation nor destabilization was observed after several days. The reactivity ratios for rTFMA and rVDF were 0 and 1.6 at 80 °C, respectively.
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