The principle and calculation equation of composition distribution measurement for vinyls/ N phenylmaleimide(PMI) copolymer were presented using the information of differential refractometer (DR) and ultraviolet spectrophotometer(UV) detectors connected with the gel permeation chromatography(GPC). With the information of DR and UV detectors, the effects of copolymerization methods and process on the composition distributions of styrene PMI, methyl methacrylate PMI and vinyl chloride PMI copolymers systems were studied. It was found that the composition distribution of copolymer was even at low conversion, but changed with the increasing of conversion. [WT5HZ]
