Abstract: High-resolution ¹³C NMR spectra of atactic polyacrylonitrile (PAN) and isotactic-rich PAN were obtained under optimized solution concentration and experimental temperature. Assignments of nitrile carbon atoms with heptads were obtained and shown to be different from previously reported. The methenyl carbon atoms with pentads and heptads were assigned, respectively. It was shown that the atactic PAN obeys Bernoullian statistics. First-order and second-order Markov statistics were applied to calculate the content of the n-ads in isotactic-rich PAN. The number-average lengths of the isotactic and syndiotactic sequences calculated by “block” statistics confirmed the assignments of the heptads by ¹³C NMR spectroscopy.

Key words: NMR, chemical shift, ¹³C spectra, polyacrylonitrile, stereosequence, heptad