A maleimide monomer with benzoxazine and nitrile functionalities, 1-[3-(4-cyano-phenyl)-3,4-dihydro-2H-benzo[e] [1,3]oxazine-6-yl]-maleimide (MI-Bz-4CN), was prepared using N-(4-hydroxyphenylmaleimide) (HPMI), formaldehyde, and 4-aminobenzonitrile. Photoinduced radical polymerization was employed to prepare the alternating copolymers of MI-Bz-4CN with styrene (St) at room temperature using omega, omega-dimethoxy-omega-phenylacetophenone (DMPA) as photoinitiator. These polymers were characterized by FT-IR and H-1 NMR. Monomer reactivity ratios for the studied monomer pair were calculated by using extended Kelen-Tddos (Ex. K-T) method. Structural parameters of the copolymers were obtained calculating the diad monomer sequence fractions. Copolymers' compositions and. the monomer reactivity ratios suggest the alternating nature of the copolymerization. Thermal behavior of the alternating copolymers P(MI-Bz-4CN-alt-St) was also investigated by thermogravimetrical analysis (TGA) and differential scanning calorimetry (DSC). The ring-opening polymerization of the pendant benzoxazine groups of the copolymers was monitored by DSC and FT-IR studies. (c) 2007 Wiley Periodicals, Inc.