Analysis of Vinyl Acetate-Ethylene Copolymers by High Resolution NMR

Several samples of vinyl acetate (VA)-ethylene (E) copolymers (PEVA) having different monomer compositions were prepared by solution polymerization in ethyl acetate. A quantitative method for determining the ethylene contents in PEVA was examined by high resolution NMR spectroscopy and the results were compared with those of analyses on a method of alkaline hydrolysis. The NMR spectra of PEVA were measured at 100 MHz. in several different solvents. For the solvent of PEVA, cis-1, 2-dich-l oroethylene was chosen since the resonance peaks of acetoxymethyl protons and methylene protons were most clearly resolved in this solution. The results by the NMR spectroscopy showed good agreement with analyses by the alkali ne hydrolysis. The NMR method can be used for quantitative analysis of PEVA without any addition of intensity reference material. The sequence distributions of monomer units in the series of PEVA can be also determined by the NMR method. Run-numbers (Robs), distributions of monomer diads and sequence lengths of monomer units were measured. These PEVA were found to have statistically random sequence distrib utions of monomer units.