Ac. Kolbert et Jg. Didier, CHARACTERIZATION OF MECHANICALLY SHEARED ETHYLENE-PROPYLENE COPOLYMERS BY HIGH-RESOLUTION NMR, Journal of polymer science. Part B, Polymer physics, 35(12), 1997, pp. 1955-1961
We report high-resolution solution-state NMR experiments on chain ends
generated in ethylene-propylene copolymers by mechanical shearing in
an extruder. The use of the higher resolution of the C-13-NMR spectrum
, in a two-dimensional H-1-C-13 chemical shift correlation experiment,
has allowed the complete resolution and assignment of the olefinic ch
ain-end region of the H-1-NMR spectrum. Simultaneously, the assignment
s of the C-13 olefinic resonances, previously identified [A. C. Kolber
t, J. G. Didier, and L. Xu, Macromolecules, 29, 8591 (1996)] are confi
rmed. An iterative method for calculating the average molecular weight
, based on quantitative measurements of the olefinic 1H-NMR peak inten
sities is introduced and these results are compared with measurements
from C-13-NMR and size exclusion chromatography and correlated to redu
ced viscosities. (C) 1997 John Wiley & Sons, Inc.