Chemical heterogeneity analysis of high-conversion poly[styrene-co-(ethyl acrylate)]s by NMR and on-line coupled SEC-NMR

Abstract

Copolymers of styrene and ethyl acrylate are prepared by radical polymerization and analysed with respect to microstructure by means of nuclear magnetic resonance. Using 13C NMR, the compositional styrene- and ethyl acrylate-centered triads can be determined and compared to theoretical values. Good agreement between experimental and calculated triad concentrations are obtained for styrene-rich copolymers. Ethyl acrylate-rich copolymers exhibit significant deviations from the calculated values in particular for the ethyl acrylate homotriads. Using on-line coupled SEC-1H NMR, the chemical composition across the molar mass axis can be monitored. It is found that ethyl acrylate-rich copolymers exhibit a broader molar mass and chemical composition distribution than styrene-rich copolymers. The results indicate that the block character of the copolymers with respect to ethyl acrylate units increases with increasing molar mass.