Iodine Transfer Terpolymerization of Vinylidene Fluoride, α-Trifluoromethacrylic Acid and Hexafluoropropylene for Exceptional Thermostable Fluoropolymers/Silica Nanocomposites

Abstract

The synthesis of poly(VDF-ter-TFMA-ter-HFP) terpolymers (where VDF, TFMA, and HFP stand for vinylidene fluoride, α-trifluoromethacrylic acid, and hexafluoropropylene, respectively) and their blends with silica filler for preparing original fluorocomposites are presented. First, the radical terpolymerization of VDF, TFMA, and HFP by iodine transfer polymerization without any surfactant was investigated in the presence of 1,6-diiodoperfluorohexane as the chain transfer agent. TFMA monomer was well incorporated, and the terpolymers were obtained in good yields (>65%). The microstructures of the produced terpolymers were characterized by 1H and 19F NMR spectroscopy to assess the amounts of each comonomer, the molecular weights, and the nature of the end groups of the copolymers. Molar percentages of VDF, TFMA, and HFP were in the 45−80, 12−53, and 1−8 ranges, respectively, whereas the molecular weights of the resulting terpolymers were ca. 5400−12 600 g·mol−1. End groups were VDF-I only with a high amount of CH2CF2−I. Then, these poly(VDF-ter-TFMA-ter-HFP) terpolymers were involved in the preparation of the fluorinated polymers/silica nanocomposites by sol−gel reactions in the presence of tetraethoxysilane and silica nanoparticles under alkaline and acidic conditions, respectively. Interestingly, poly(VDF-ter-TFMA-ter-HFP) terpolymer/silica nanocomposites, which were prepared under alkaline conditions, showed exceptional thermal properties because they were found to exhibit almost no weight loss up to 800 °C.