The thermal cure reactions of phenylethynyl terminated AFR-PEPA-4 oligomer and a model compound N-phenyl-[4-(phenylethynyl) phthalimide] were investigated. The kinetics analysis of the thermal cure of AFR-PEPA-4 was determined using DSC, with modified DiBenedetto equation. The activation energy of thermal cure reaction of AFR-PEPA-4 oligomer is 34.1 kcal/mol with the kinetic order of one, when the reaction conversion is less than 80%. The activation energy of thermal reaction of N-phenyl-[4-(phenylethynyl) phthalimide] is 41.5 kcal/mol with the kinetic order of 0.95. The cure reaction of AFR-PEPA-4 imide oligomer can be described as a fast first-order reaction stage for the formation of polyenes followed by a slow diffusion-controlled crosslinking reaction stage. (c) 2006 Wiley Periodicals, Inc.