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NMR spectra of polyimides: Interpretation and local chain motion study
Author(s) -
Wang Jianli,
Zhang Jianguo,
Li Binyao,
Ding Mengxian,
Feng Zhiliu
Publication year - 1996
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/macp.1996.021970220
Subject(s) - polyimide , chemistry , imide , phenyl group , polymer chemistry , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , methyl group , crystallography , analytical chemistry (journal) , stereochemistry , group (periodic table) , physics , organic chemistry , alkyl , halogen , layer (electronics)
Three kinds of high‐performance polyimides 1 (poly(ketone‐imide) PKI), 2 (poly(ether‐imide) PEI) and 3 (poly(oxy‐imide) POI) were studied using nuclear magnetic resonance (NMR). The NMR spectra of the polyimides were assigned according to the comprehensive consideration of the substitution effect of different substituting groups, viz. distortionless enhancement by polarization transfer (DEPT), no nuclear Overhauser effect (NNE), analysis of relaxation time, and two‐dimensional correlated spectroscopy (COSY) techniques. The structural units of these three polyimides were determined. Carbon‐13 and proton relaxation times for PEI and PKI were interpreted in terms of segmental motion characterized by the sharp cutoff model of Jones and Stockmayer (JS model) and anisotropic group rotation such as phenyl group rotation and methyl group rotation. Correlation times for the main‐chain motion are in the tens of picosecond range which indicates the high flexibility of polyimide chains. Correlation times for phenyl group and methyl group rotations are more than 1 order of magnitude lower and approximately 1 order of magnitude higher than that of the main chain, respectively.