ISSN:
0887-624X
Schlagwort(e):
cyclic olefin copolymers
;
norbornene
;
metallocene catalysts
;
NMR
;
microstructure
;
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Norbornene-ethylene copolymers were prepared using the metallocene catalyst ethylene bis (indenyl) zirconium dichloride with MAO, and their microstructure was characterized with 1H-NMR and 13C-NMR methods. From a Cosy 1H-NMR spectrum it was found that all norbornene units are enchained in the exo-configuration. The sequence distribution of norbornene units was investigated using 13C-1H correlations, hmqc for one-bond correlations, and hmbc for two- or three-bond correlations. It was shown that norbornene diads were formed at a high norbornene content (45 mol %). When further increasing the norbornene incorporation (66 mol %) a number of new signals were obtained. A Cosy 1H-NMR spectrum revealed a new crosspeak which, according to the corresponding 13C-NMR shifts (hmqc), correlated well with a terminal unit of a trimer of norbornene. This means that at very high norbornene contents, norbornene triads can be formed. Because the formation of isotactic norbornene triads is very difficult to understand from a sterical point of view, an epimerization process causing stereoirregularities in the norbornene triad is proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1633-1638, 1998
Zusätzliches Material:
8 Ill.
Materialart:
Digitale Medien
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