Characterization of Backbone Structures in Poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) Copolymers by Multidimensional ¹⁹F NMR Spectroscopy

Advanced modern multidimensional solution NMR experiments have been used to deduce the sequence distribution in poly­(VDF-<i>co</i>-HFP) copolymers. Assignment of ¹⁹F resonances from different monomer- and regio-sequences in poly­(VDF-<i>co</i>-HFP) copolymer were identified. In addition to corroborating some assignments reported in earlier literature, this work provides assignments of some new resonances from the spectra of poly­(VDF-<i>co</i>-HFP) copolymer, which resulted from better dispersion of the resonances. These assignments are used for the monomer sequence analyses of two polymers using first-order Markovian statistics, and the relative reactivities of the monomers during polymerization are discussed. The results from this study provide insight into the polymerization chemistry for this fluoropolymer

Characterization of Backbone Structures in Poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) Copolymers by Multidimensional ¹⁹F NMR Spectroscopy

Advanced modern multidimensional solution NMR experiments have been used to deduce the sequence distribution in poly­(VDF-<i>co</i>-HFP) copolymers. Assignment of ¹⁹F resonances from different monomer- and regio-sequences in poly­(VDF-<i>co</i>-HFP) copolymer were identified. In addition to corroborating some assignments reported in earlier literature, this work provides assignments of some new resonances from the spectra of poly­(VDF-<i>co</i>-HFP) copolymer, which resulted from better dispersion of the resonances. These assignments are used for the monomer sequence analyses of two polymers using first-order Markovian statistics, and the relative reactivities of the monomers during polymerization are discussed. The results from this study provide insight into the polymerization chemistry for this fluoropolymer

2D-NMR Characterization of Sequence Distributions in the Backbone of Poly(vinylidene fluoride-<i>co</i>-tetrafluoroethylene)

NMR is a powerful tool to study the microstructures of poly­(vinylidene fluoride-<i>co</i>-tetrafluoroethylene), poly­(VDF-<i>co</i>-TFE). This study shows that the microstructures in this copolymer can be established completely on the basis of 2D-NMR, in which improved dispersion is achieved by the second dimension (¹⁹F or ¹³C chemical shifts). 2D-NMR has been proven to be extremely effective for identifying the carbon sequence distributions in the polymer main chain. For lower level sequences (3- or 5-carbon sequences), resonance assignments on the basis of one- and two-bond ¹⁹F­{¹³C} gradient heteronuclear single quantum coherence (gHSQC) experiments are in good agreement with assignments obtained by traditional methods. Higher level sequences (7- or 9-carbon sequences), which can not be assigned unambiguously by traditional methods, were determined by ¹⁹F–¹⁹F gradient double quantum correlation spectroscopy (gdqCOSY), which provides ¹⁹F–¹⁹F correlations over 3–5 bonds. A quantitative study was also conducted on the composition of this copolymer. Three different approaches were used to calculate the fraction of TFE and the inversion ratio of VDF units