Characterization of end groups and branching structures in copolymers of vinylidene fluoride with hexafluoropropylene using multidimensional NMR spectroscopy

• Detailed 2D 19F NMR characterization of end groups in poly(VDF-co-HFP) copolymers.
• Use of 2D DOSY to distinguish between long chain branches and short chain branches.
• End groups in poly(VDF-co-HFP) copolymers quantified with NMR spectroscopy.

19F and 1H NMR experiments have been used to assign the resonances of end groups and branching structures in poly(VDF-co-HFP) copolymer. Multidimensional NMR experiments, spin–lattice relaxation (T1) analysis, and diffusion ordered spectroscopy (DOSY) NMR were used as complementary NMR methods to identify and also to obtain the structures of the end groups in these copolymers. Resonances of chain branching structures (long chain branch (LCB) and short chain branch (SCB)) were also identified with T1 and 2D DOSY NMR experiments; other 2D NMR experiments, such as selective COSY (correlation spectroscopy) and gradient heteronuclear single quantum coherence (gHSQC) were used to provide atomic connectivity information to determine resonance assignments. The amount of each end group in the poly(VDF-co-HFP) copolymers was quantified with the aid of an internal reference, 1,4-dichloro-2-(trifluoromethyl)benzene. The –CH2CF2H end group was found to be the most prevalent in the copolymers studied.

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