Deeper Spectroscopic Characterizations of Vinylidene Fluoride (VDF) Oligomers Prepared via Iodine Transfer Polymerization (ITP)
Résumé
The iodine transfer polymerization of vinylidene fluoride (or 1,1-difluoroethylene, VDF) controlled by 1-iodoperfluoroalkanes or 1,8-diiodoperfluoroctane led to oligo(VDF)s containing one or two iodine end-atom(s). Their deep characterizations utilizing size exclusion chromatography (SEC or GPC), 1 H, 19 F NMR, and FT-IR spectroscopies, matrix-assisted laser desorption-ionization time of flight mass spectrometry (MALDI-TOF) unveiled low dispersities, indicating a pseudo-living nature of the reaction. In addition, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) deeply facilitated the identification of various oligo(VDF) structures, specially R F (VDF) n I and side R F (VDF) n H oligomers. From the 19 F NMR spectra, the signals assigned to CF 3 and CF 2 I end groups are valuable labels to determine the number-average molar masses (M n ) of such VDF oligomers. The 19 F NMR, FT-ICR MS and MALDI-TOF MS evidenced a good agreement in terms of the VDF unit numbers and endgroups. while their head to head and tail to tail VDF-VDF defect of chainings, calculated from NMR data, were quite low (4.0% and 1.2%, respectively). Although the controlled behavior of these ITPs was not studied, the dispersities of the resulting oligo(VDF) were rather narrow (1.16-1.52) for molar masses reaching up to 4,300 g.mol -1 . Their thermal characteristics, achieved by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) evidenced crystalline oligo(VDF)-I with increasing melting points (up to 169 °C) and increasing thermal stabilities (up to 365 °C under air) for M n values ranging from 1,300 to 4,300 g.mol -1 .