C-13 NUCLEAR MAGNETIC-RESONANCE INVESTIGATION OF ETHYLENE HOMOPOLYMERS, COPOLYMERS AND MODEL SYSTEMS - CHEMICAL-SHIFTS AND RELAXATION-TIMES

This is a report on the use of **1**3C NMR spectroscopy to study the structure of polyethylenes, polyethylene-olefin copolymers, and polyethylene model systems, through the observation of chemical shifts and spin-lattice relaxation times of individual carbons. Information is obtained on the type and numbers of side chains of polyethylenes from solution spectra at higher temperatures. The level of detectability of side chains is established at 2 side chain carbons per 1000 skeletal carbons. The observed chemical shifts are accounted for well by standard additivity schemes. The low-density polyethylenes show spectra which are distinctly different from high-density polyethylenes.