Infrared Absorption Spectra of Polyacrylonitrile and Deuterated Polyacrylonitriles

Polarized infrared spectra of polyacrylonitrile (PAN), -(-CH2-_??_-) n-, poly-α-deuteroacrylonitrile-(-CH2-_??_-) n-, poly-β, β-dideuteroacrylonitrile-(-CD2-_??_-) n-and poly-α, β, β-trideuteroacrylonitrile-(-_??_-CD-) n-have been measured in the region from 4000 to 200cm-1.β, β-dideuteroacrylonitrile was prepared by the hydrogen exchange reaction of α, β, β-trideuteroacrylonitrile with H2O in the presence of CaO. Reasonable shifts of the C-H stretching bands of PAN were observed by deuteration. The normal vibrations of PAN and deuterated PAN's were calculated under the simplest assumption of the syndiotactic and planar zigzag structure. The calculation was made by the use of GF matrix method with the Urey-Bradley force field. Fairly good agreements between the observed and the calculated frequencies were obtained. The assignments of the bands are given and discussed.