Structural analysis of vinylidene fluoride-tetrafluoroethylene copolymers by NMR spectroscopy.

The application of high-resolution NMR spectroscopy to the structural analysis of copolymers is illustrated by a detailed investigation of the vinylidene fluoride (VF(2)) - tetrafluoroethylene (F(4)E) system. Copolymers of VF(2) with F(4)E are of topical interest owing to their ferroelectric behavior, and NMR provides the only method to accurately determine their composition and chemical microstructure. Many copolymer properties are highly sensitive to these structural variables, which must be characterized prior to the evaluation of physical behavior. A series of copolymers with compositions ranging from 100- 50 mol% VF(2) is analyzed by proton, carbon-13, and fluorine- 19 NMR. Proton and carbon-13 NMR experiments distinguish monomer sequence triads. Fluorine-19 NMR is the method of choice for the most detailed analysis, as this probe resolves all monomer sequence pentads, as well as some longer-range sequences.