Microstructure determination of N-vinyl-2-pyrrolidone/butyl acrylate copolymers by NMR spectroscopy

The copolymer composition of N-vinyl-2-pyrrolidone/butyl acrylate (V/B) copolymers was determined from the quantitative ¹³C{¹H} NMR spectra. The monomer reactivity ratios for N-vinyl-2-pyrrolidone (V) and butyl acrylate (B) were found to be r_V=0.11±0.07, r_B=0.54±0.19, using the Kelen–Tudos and non-linear least-square error-in-variable (EVM) methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers are overlapping and complex. The complete spectral assignment of the carbon and proton NMR spectra were done by employing distortionless enhancement by polarization transfer (DEPT) and two-dimensional (2D) ¹³C–¹H heteronuclear single quantum correlation spectroscopy experiments. The 2D total correlation spectroscopy (TOCSY) (¹H–¹H homonuclear TOCSY) NMR spectrum was used to ascertain the various geminal and vicinal couplings in the copolymer.