Abstract: Because of the background absorbance of stearyl poly(ethylene oxide), big errors arise when normal UVspectrometry is used to determine the polystyrene content of polystyrene-g-stearyl poly (ethylene oxide) (PS-g-SPEO).In order to eliminate the interference of SPEO, we developed the first derivative UV spectrometry for the quantitative composition determination of PS-g-SPEO.It was discovered that the undesirable background absorbance mentioned above could be completely eliminated and the compositions of PS-g-SPEO copolymers determined from the first derivative spectrometry coincide quite well with the data derived from elementary analysis.The results indicate that the nrst derivative UVspectrometry is a feasible and accurate method for the composition determination of polystyrene-based copolymers.

Key words: The derivative UV spectrcmetry, Composition determination of copolymers, Polystyrene-based copolymer