Thermal behavior of carbon fiber precursor polymers with different stereoregularities

The effect of stereoregularity, in terms of isotactic triad content on the thermal behavior of carbon fiber precursor polymers synthesized through different polymerization routes such as solid state and radical solution polymerization techniques, was investigated by the thermogravimetric analysis and differential scanning calorimetric measurements. The isotactic contents of I-PAN and A-PAN were estimated with C-13 NMR. The thermal cyclization reactions of atactic polyacrylonitrile (A-PAN) with low isotactic content (26.4-29.7 %) occurred at a lower temperature than that of isotactic polyacrylonitrile (I-PAN) with higher content (48.7-51.6 %). The percentage of mass loss observed in I-PAN was less as compared to A-PAN. The molecular mass characteristics of PAN obtained through solid state and radical solution polymerization were [M (n) (10.2-14.3 x 10(4)), M (v) (2.44-3.26 x 10(5))] and [M (n) (10.2-14.3 x 10(4)), M (v) (2.29-2.74 x 10(5))] Daltons (Da).