Effect of acrylonitrile sequence distribution on the thermal stabilization reactions and carbon yields of poly(acrylonitrile-co-methyl acrylate)

Polyacrylonitrile (PAN) copolymers are important precursors for making high performance carbon fibers. In this study, a type of inert comonomer, methyl acrylate (MA), was copolymerized with AN, and the effects of AN sequence distribution on the cyclization, oxidation and carbon yield were systematically studied. The sequence distribution of P(AN-co-MA) could be adjusted by altering MA/AN feeding ratio during radical polymerization. The number-average sequence length of AN in the copolymers decreases quickly along with the increase of MA content in PAN. The stabilization and carbonization weight losses were determined by thermogravimetric analysis, and the corresponding chemical changes were detected by Fourier transform infrared spectrums and X-ray photoelectron spectroscopy. The thermal cyclization and oxidation reactions were separated by altering gas environment from nitrogen to air, and were monitored by differential scanning calorimetry. It is concluded that the sequence distribution of AN in P(AN-co-MA) strongly affects reaction activation energies, cyclized structures and carbon yield.