Premium
13 C NMR Studies of Ethene/Norbornene Copolymers using 13 C‐Enriched Monomers: Signal Assignments of Copolymers Containing Norbornene Microblocks of up to a Length of Three Norbornene Units
Author(s) -
Wendt Ralf Alexander,
Fink Gerhard
Publication year - 2001
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20011201)202:18<3490::aid-macp3490>3.0.co;2-6
Subject(s) - norbornene , copolymer , monomer , metallocene , polymer chemistry , carbon 13 nmr , nmr spectra database , materials science , chemistry , ethylene , polymerization , catalysis , spectral line , organic chemistry , polymer , physics , astronomy
Ethene and norbornene were copolymerized at 0.8 bar ethene absolute pressure using metallocene catalysts that produce microstructures containing norbornene blocks, particularly rac‐ Me 2 Si[Ind] 2 ZrCl 2 /MAO, i Pr[CpFlu]ZrCl 2 /MAO and i Pr[CpInd]ZrCl 2 /MAO. Intensive 13 C NMR spectroscopic investigations of the obtained copolymers were performed and norbornene di‐ and triblock sequences detected clearly. Several copolymerization experiments were carried out by using 13 C 1 ‐enriched ethane, or 13 C 5/6 ‐enriched norbornene, respectively. Thus, resonances of the norbornene carbon atoms C5/C6 and the ethene carbon atoms Ca/Cb, which overlap extensively in the 13 C NMR spectra, could clearly be differentiated. In addition, further copolymerizations with natural monomers were performed at 2 bar ethene excess pressure to investigate the influence of the monomer concentration on the microstructure. By comparing the 13 C NMR spectra of copolymers obtained under different conditions, assignments of most resonances were achieved. These 13 C NMR studies made it possible to assign norbornene triblock resonances with differing stereochemical connections such as meso , meso and rac , meso which have not been mentioned in previous works. The results led to new insights about the copolymer microstructure and allow development of a scheme showing the ethene/norbornene microstructures depending on the various catalyst systems utilized, including the metallocenes i Pr[(3‐ i Pr‐Cp)Flu]ZrCl 2 and i Pr[(3‐ tert ‐But‐Cp)Ind]ZrCl 2 which have been applied in previous publications.