Deeper Spectroscopic Characterizations of Vinylidene Fluoride (VDF) Oligomers Prepared via Iodine Transfer Polymerization (ITP)

Abstract

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), H-1 and F-19 NMR and FT-IR spectroscopies, and matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF) revealed low dispersities, indicating a pseudoliving 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, especially R-F(VDF)(n)I and side R-F(VDF)(n)H oligomers. From the F-19 NMR spectra, the signals assigned to the CF3 and CF2I end groups are valuable labels to determine the number-average molar masses (M-n) of such VDF oligomers. The F-19 NMR, FT-ICR MS, and MALDI-TOF MS data evidenced good agreement in terms of the VDF unit numbers and end groups, 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 iodine transfer polymerizations (ITPs) was not studied, the dispersities of the resulting oligo(VDF) species were rather narrow (1.16-1.52) for molar masses reaching up to 4300 gmol(-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 degrees C) and increasing thermal stabilities (up to 365 degrees C under air) for M-n values ranging from 1300 to 4300 gmol(-1).