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

Abstract

SUMMARY: Copolymers of styrene and ethyl acrylate are prepared by radical polymerization and analysed with respect to microstructure by means of nuclear magnetic resonance. Using 13 C 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-1 H 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.

Molar Mass and Microstructure Analysis of PI‐b‐PMMA Copolymers by SEC‐NMR

“…The possibility to obtain CCD information by SEC‐NMR has been shown both for block5, 6, 18, 19 and random copolymers 18. Further studies deal with the chemical heterogeneity of random copolymers20 or stereocomplexes built from mixtures of isotactic and syndiotactic PMMA 21. It was also demonstrated that microstructure analysis with respect to retention time could be done by SEC‐NMR, delivering insight into the corresponding polymerization process 5, 16, 22…”

On-line coupling of high temperature GPC and 1H NMR for the analysis of polymers

“…In further studies on copolymers, gradient HPLC-NMR was used for the analysis of the CCD of random poly(styrene-co-ethyl acrylate) copolymers [13]. The same copolymer system was also studied by GPC-NMR [14].…”

A Critical Overview of Sensors for Monitoring Polymerizations

“…Another step151 proved that plots of intensities of the α ‐proton resonances versus elution time could show the variation of tacticity with molecular weight changes in the sample. Afterwards, Ute et al154, 155 studied stereocomplexes of isotactic and syndiotactic poly(MMA) samples using the same approach and Kramer et al156 looked at the microstructure of high‐conversion STY/EA copolymers using on‐line coupled GPC/NMR. Pasch and Hiller157 studied the chemical structure and degree of polymerization of poly(ethylene oxide) (PEO).…”