New aspects on the cyclization mechanisms of Poly(acrylonitrile-co-itaconic acid)

Poly(acrylonitrile-co-itaconic acid) (PAI) is the most widely used precursor for making high performance carbon fiber. In this study, we synthesized PAI with various contents of itaconic acid (IA) in the range of 0 to 22 mol%. The addition of IA not only changes acrylonitrile (AN) segment length distribution, but also initiate AN cyclization at a lower temperature. The effects of PAI sequence distribution and initiation mechanisms on PAN cyclization were systematically studied by differential scanning calorimetry, nuclear magnetic resonance, Fourier transform infrared spectroscopy and thermogravimetry. These results show how the AN sequence length and the carboxyl groups in IA affect the cyclization reaction, the formed ladder structures, and carbon yields.