CHARACTERIZATION OF MECHANICALLY SHEARED ETHYLENE-PROPYLENE COPOLYMERS BY HIGH-RESOLUTION NMR

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.