Abstract
The synthesis of original fluorinated (co)telomers containing vinylidene fluoride (VDF) or VDF and hexafluoropropene (HFP) was achieved by radical telomerizations and (co)telomerizations of VDF (or VDF and HFP) in the presence of 1, 6-diiodoperfluorohexane via a semisuspension process. tert-Butyl peroxypivalate (TBPPi) was used as an efficient thermal initiator. The numbers of VDF and VDF/HFP base units in the (co)telomers were determined by 19F and 1H NMR spectroscopy. They ranged from 10 to 190 VDF base units. Fluorinated telomers of various molecular weights (1200– 12,600 g/mol) were obtained by the alteration of the initial [1,6-diiodoperfluorohexane] 0/[fluoroalkenes]0 and [TBPPi]0/[fluoroalkenes]0 molar ratios. The thermal properties of these fluorinated (co)telomers, such as the glass-transition temperature and melting temperature, were examined. As expected, these telomers exhibited good thermal stability. They were stable at least up to 350 8C. The compounds containing more than 30 VDF units were crystalline, whereas all those containing VDF-co-HFP were amorphous with elastomeric properties, whatever the number was of the fluorinated base units. The structures of I–(VDF)n–RF–(VDF)m–I and I–(HFP)x(VDF)n–RF– (VDF)m(HFP)y–I (co)telomers were obtained, and the defects of the VDF chain and the CH2CF2I and CF2CH2I functionalities were studied successfully (where RF ¼ C6F12). The functionality in the iodine atoms was modified: the higher the VDF content in the telomers, the lower the normal end functionality (CH2CF2I) and the higher the reversed extremity (CF2CH2I). In addition, the percentage of defects increased when the number of VDF units increased. The molecular weights and molecular weight distributions of different telomers and cotelomers were also studied.