Sequence distributions of vinyl chloride‐vinyl acetate and vinyl chloride‐vinyl propionate copolymers

Abstract

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.

300-MHz Proton NMR and 25-MHz carbon-13 NMR investigations of sequence distributions in vinyl alcohol-vinyl acetate copolymers

“…For a structurally related polymer, vinyl chloride-vinyl acetate copolymer, the NOEs emd spin-lattice relaxation times for the different types of carbons (excluding the carbonyl carbon) in or near the copolymer main chain have been measured. 9 The NOEs for all proton-bearing c arbons agree within experimental error with the theoretically calculated maximum value. No differential NOEs were observed for the methylene carbons.…”

Compositional sequence distribution, cotacticity, and second-order Markov statistics in vinyl chloride-vinyl acetate copolymers

“…The values for the methine, methylene, and methyl carbons are (VA = 0.22) 0.12, 0.06, and 0.80 s, respectively, and increase slightly with increasing VA content. 1 Bearing this in mind, we have run these copolymers with a long delay time (5 s) and calculated the copolymer composition via measurements of methyl and methine carbon peak areas and via measurements of the VCand VA-centered methine carbon peaks separately. The results are identical with those obtained via NMR.…”