The imidization of poly(styrene-co-maleic anhydride) with amines may improve some of its end-use properties. The objective of this study was to examine the mechanism and kinetics with aniline (ANL) as an amine of the preparation of poly(styrene-co-N-phenyl maleimide). The reaction was carried out in a tetrahydrofuran solution at 25-55 degrees C and in an ethylbenzene solution at 85-120 degrees C. The extent of the reaction was determined by conductance titration, a new and simple method. Two consecutive reactions were involved in the imidization: ring opening to produce an acido-amide group and ring closing to form a corresponding imide group. The imidization rate was greatly influenced by the reaction temperature and the molar ratio of ANL to the anhydride. A model for the imidization kinetics over a wide range of reaction temperatures and concentration ranges was developed and validated. (c) 2006 Wiley Periodicals, Inc.