Theoretical study of the dependence of the valence electronic levels on the tacticity and conformation of acrylonitrile model oligomers

With the aim of searching for signatures of conformation and tacticity in electrodeposited polyacrylonitrile valence XPS spectra, exploratory ab initio STO-3G calculations have been performed on four model structures of H—[CH2—CH(CN)]6—H: isotactic and syndiotactic all-trans planar chains and isotactic and syndiotactic (TG)3 helical chains. Contrary to what was assumed in earlier work it is found that the (TG)3 conformation is not a suitable model helix for polyacrylonitrile. Signatures of conformation and tacticity are noted in the ab initio simulated valence XPS spectra; their characteristic features (position on the energy scale, shape and intensity) are within the limits of experimental resolution.