Multidimensional ¹⁹F NMR Analyses of Terpolymers from Vinylidene Fluoride (VDF)–Hexafluoropropylene (HFP)–Tetrafluoroethylene (TFE)

The use of multidimensional NMR methods for the characterization of polymer microstructure has been applied to terpolymers from vinylidene fluoride (VDF), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE). By assembling the atomic connectivity information obtained from different multidimensional NMR experiments, selective ¹⁹F–¹⁹F COSY (correlation spectroscopy), ¹⁹F–¹⁹F gradient double-quantum COSY, and ¹⁹F–¹³C gradient heteronuclear single-quantum coherence (gHSQC), among others, the detailed monomer sequence arrangements in the terpolymer were obtained. Obtaining the resonance assignments of the terpolymer was greatly aided by the extrapolation of known resonance assignments from PVDF homopolymer, poly­(VDF-<i>co</i>-HFP) copolymer, and poly­(VDF-<i>co</i>-TFE) copolymer. A tabulated comparison of the microstructure assignment of resonances from PVDF homopolymer as well as poly­(VDF-<i>co</i>-HFP) and poly­(VDF-<i>co</i>-TFE) copolymers and the terpolymer is provided. Detailed comparisons of ¹⁹F spectra from 470 and 658.4 MHz spectrometers, revealing the AB patterns present in this terpolymer, are presented and discussed in this paper. The compositions of the comonomers in the terpolymers were calculated with different methods, all of which gave similar values. The percentages of VDF and HFP monomer inversions in the terpolymers were also calculated from the assigned NMR resonances

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

NMR Study of the Chain End and Branching Units in Poly(vinylidene fluoride-<i>co</i>-tetrafluoroethylene)

2D-NMR techniques were used to identify the detailed structures of chain end and branching units in poly­(vinylidene fluoride-<i>co</i>-tetrafluoroethylene), poly­(VDF-<i>co</i>-TFE). Atomic connectivity information was provided by selective ¹⁹F–¹⁹F COSY (correlation spectroscopy), ¹⁹F­{¹H} gHETCOR (gradient heteronuclear correlated), and ¹H­{¹³C} HSQC (heteronuclear single quantum correlation) experiments. Diffusion ordered spectroscopy (DOSY) and spin–lattice relaxation (<i>T</i>₁) data permitted distinction of backbone, short chain branch, and chain end resonances from one another. Quantitative data on these structures are reported; quantitation also supported assignments through the consistent relative intensities of resonances from the same structures. Possible reactions during the polymerization which could lead to these structures are discussed

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

Characterization of the Chain-Ends and Branching Structures in Polyvinylidene Fluoride with Multidimensional NMR

Multidimensional solution NMR (¹⁹F, ¹H, and ¹³C) has been used to determine chain-ends and backbone branching points and to obtain unambiguous ¹⁹F and ¹H resonances assignments from these chain-ends and branching structures in poly­(vinylidene fluoride) (PVDF). The multidimensional NMR methods employed in this study not only enabled the resonance assignments of the last monomer of the chain but also provided assignments for the last three monomer units of chain-end structures. The chain-end signals from PVDF were determined using spin–lattice relaxation measurements and 2D diffusion ordered spectroscopy (DOSY) analysis. 2D-NMR analyses were also used to assign resonances of chain branching points along the backbone of the polymer