The synthesis and characterization of vinylidene fluoride-tetrafluoroethylen e copolymers.

We have prepared copolymers of vinylidene fluoride (VF(2)) with tetrafluoroethylene (F(4)E) over a wide composition range by an emulsion technique. The chemical microstructure has been determined by 470.7 MHz (19)F NMR, which resolves regiosequence detail up to the nonad level. The sequence fine structure has been fully assigned by treating the system as a terpolymerization involving forward and reverse VF(2) addition as well as F(4)E addition, and extending our assignments made for aregic PVF (2) homopolymer. The crystalline structures of the copolymers at room temperature show gradual changes from that of beta- PVF(2) to that of PF(4)E as the proportion of VF(2) is decreased. Compositions above ~82 mol% VF(2) show no phase transitions during heating and cooling between room temperature and their melting points. Between ~70-82 mol% VF(2), clear Curie transitions are seen that decrease in temperature with decreasing amounts of VF(2). Below ~70 mol% VF(2), more gradual transitions involving intermediate phases are obtained, as a result of the increasing influence of F(4)E units.