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Unsaturation Characterization of Polyolefins by NMR and Thermal Gradient NMR (TGNMR) with a High Temperature Cryoprobe
Author(s) -
Zhou Zhe,
Cong Rongjuan,
He Yiyong,
Paradkar Manjiri,
Demirors Mehmet,
Cheatham Mike,
deGroot A. Willem
Publication year - 2012
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.201100015
Subject(s) - degree of unsaturation , polyolefin , proton nmr , carbon 13 nmr , characterization (materials science) , chemistry , materials science , nuclear magnetic resonance spectroscopy , analytical chemistry (journal) , organic chemistry , nanotechnology , layer (electronics)
Summary: It is important to identify the types of unsaturation and to quantify the amount of unsaturation in polyolefins for understanding chain termination mechanisms of polymerization with different catalysts. Unsaturation is also closely related to processibility, weatherability of polyolefin products and the level of antioxidants to be added for stabilizing purposes. However, it can be very challenging to accurately measure samples with a low level of the unsaturation within a reasonable amount of NMR acquisition time, along with some challenging technical issues, such as dynamic range with 1 H NMR. This paper reports a new method to accurately quantify unsaturation by using multi peak presaturation 1 H NMR with a high temperature NMR cryoprobe. The limit of quantification can be less than 1 unsaturation/1,000,000 carbons with about 30 min NMR acquisition. This paper also introduces a new technique, temperature gradient NMR (TGNMR) with or without substrates, to characterize unsaturation distribution directly in NMR tube upon temperature change.