ABSTRACT:The high-resolution 1H-NM R spectra of poly(ethylene-vinyl acetate) with low vinyl acetate content were measured by the use of tris (l,l,l,2,2,3,3-heptafluoro-7,7-dimethyl-l,4,6-octanedionato)europium(III) as a shift reagent. As a result, the peak assigned to the acetate methyl protons was split into a triplet, and the peak assigned to the methine proton was split into a quintet and a broad peak. These split peaks were tentatively assigned to the acetate methyl and the methine protons of the central vinyl acetate unit in the triad sequences, respectively. Since the samples were determined to be random copolymers from their 1H-NM R measurements in benzene-d6, the triad concentrations were calculated by means of the random copolymerization theory. These calculated concentrations were compared with the observed concentrations for the above split peaks in the acetate methyl and methine proton signal, and the former were in close agreement with the latter.
KEY WORDSPoly(ethylene-vinyl acetate) / 1H-NM R / Shift Reagent / Eu(fod)a / Run Number / Robs / Rrand /
Abstract13C‐NMR spectroscopy was used in a detailed study of vinyl chloride‐vinyl acetate and vinyl chloride‐vinyl propionate copolymers. The NMR spectra of the methylene carbon region showed three split peaks whose intensities changed with composition of the copolymers. These peaks were assigned to diad sequences and the observed diad concentrations were in good agreement with the calculated concentrations in terms of the random copolymerization theory. For the methine carbon spectra of vinyl acetate or vinyl propionate units in the copolymers the degree of splitting of the signal was improved by the addition of tris(1,1,1,2,2,3,3‐heptafluro‐7,7‐diemthyl‐1,4,6‐octanedinata)‐praseodymium as a shift reagent. Four peaks assigned to the methine carbon were interpreted in terms of triad sequence distribution and tacticity.
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