Molecular structure of some model compounds for poly(aryl ether ketone)s

The molecular structure of a series of model compounds for poly(aryl ether ketone)s was investigated by means of 13 C NMR spectroscopy, quantum chemical calculation, and wide‐angle X‐ray scattering. The comparison of the chemical shifts for the model compounds dissolved in 98% H 2 SO 4 and CDCl 3 (or CDCl 3 + DMSO‐ d 6 ) suggested that their carbonyl groups are partially protonated by sulfuric acid and the induced positive charges are delocalized in their aromatic rings. This result was supported by the charge distribution obtained by quantum chemical calculations. The model compounds were also used to characterize the molecular structure of poly(aryl ether ketone)s. The length of the repeating unit of the polymer chain, which was calculated based on the whole chain length or fragment chain length of the model compounds obtained by semiempirical PM3 method, is compared with the c ‐axis of the crystal unit cell of the polymer. For poly(aryl ether ketone)s containing biphenyl moieties, the length of the c ‐axis of the unit cell is approximately twice that of the repeating unit of the macromolecule.