Investigation of the microstructure of metallocene-catalyzed norbornene-ethylene copolymers using NMR spectroscopy

Abstract

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

Influence of the Polymer Microstructure on the Thermal Properties of Cycloolefin Copolymers with High Norbornene Contents

“…The reason for which was quoted as being the result of differences in the polymer microstructures. Finally, Bergström et al, [11,12] hypothesised that the presence of blocks of norbornene along with alternating norbornene units result in higher T g 's due to an increased stiffness in the copolymer backbone. In conclusion, all these results insinuate that there are other factors which influence the glass transition temperature.…”

Microstructure of Copolymers of Norbornene Based on Assignments of 13C NMR Spectra: Evolution of a Methodology

“…Although in the case of poly-norbornene and of its higher oligomers, due to strong steric interactions between non-adjacent units, which induce large deformations of the torsional angles and of the ring geometry, the results of molecular mechanics show that dimers and trimers are poor models [21]. [22].…”

“…The thorough microstructure investigation of E-co-N copolymers has taken several years [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. A number of groups dedicated great efforts to assign the 13 C NMR spectra of E-co-N copolymers.…”

Solid‐state NMR study of cyclo‐olefin copolymer (COC)

“…[3][4][5][6][7][8][9][10] The polymerization temperature was controlled at 66°C with a catalyst/cocatalyst ratio ranging from 3000 to 7000, and the ethylene pressure was maintained at 19 -21 psi. The total volume of the system was 60 -65 mL during the 2 h of polymerization time.…”