A novel bifunctional comonomer 2-methylenesuccinamic acid (MLA) was synthesized to prepare poly(acrylonitrile-co-2-methylenesuccinamic acid) [P(AN-co-MLA)] copolymers, which can improve the stabilization of polyacrylonitrile significantly as a carbon fiber precursor. The structure and stabilization of P(AN-co-MLA) copolymers with different monomer feed ratios of AN/MLA were characterized by elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Reactivity ratio studies shows that MLA possesses higher reactivity than AN, resulting in higher MLA content in P(AN-co-MLA) copolymers than in the feed. The molecular weight and conversion of copolymer decrease gradually with the increase of MLA content in the feed. Comparing with PAN homopolymer, P(AN-co-MLA) copolymer has two or even three exothermic peaks, and the initial temperature of P(AN-co-MLA) copolymer is ca. 70 C lower than that of PAN, which broadens the exothermic peak. The DH/DT reduces from 34.01 J g À1 C À1 to less than 17.67 J g À1 C
À1, confirming that the incorporation of MLA can avoid centralized heat release effectively.In addition, the extent of stabilization increases as the MLA content in P(AN-co-MLA) copolymer increases under the same heat treatment conditions. The activation energy (E a ) calculation shows cyclization E a of P(AN-co-MLA) reduces from ca. 168 kJ mol À1 to ca. 110 kJ mol
À1, it is concluded that synthesized comonomer MLA can significantly improve stabilization of PAN, which is conducive to the preparation of high performance carbon fiber.