On the Structure of Poly(hexafluoro-1,3-butadiene) Yielded by Anionic Polymerization

The structure of the polymer obtained upon anionic polymerization of hexafluoro-1,3-butadiene (HFBD) was investigated by measuring solid-state ¹³C NMR spectra, X-ray photoelectron spectra (XPS), and Raman spectra. ¹³C NMR showed two peaks at 120 and 133 ppm which were assigned to the CF₃ carbon and the >C= carbon, respectively. XPS also indicated the presence of these species which were observed at 293 and 287 eV, respectively. In the Raman spectra, the vibrations at 1675 and 1145 cm^-1, which were respectively assigned to C=C and C-C stretching, were detected. The peak at 770 cm^-1 was attributed to the symmetric bending mode of the CF₃ group. Rocking and rotational vibrations assigned to the CF₃ group were also detected at 335 and 295 cm^-1, respectively. These spectral data basically agreed with those of poly(hexafluoro-2-butyne) [poly(HFBY)], which was produced under the same polymerization conditions as those used for the polymerization of HFBD. The structure of poly(HFBD) obtained here was concluded to be similar to that of poly(HFBY). The postulated polymerization mechanisms are (1) isomerization of HFBD to HFBY followed by polymerization and (2) an addition reaction of a propagating anion to the 2-carbon of HFBD followed by isomerization of the propagating end group to yield the poly (HFBY) structure.