A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
NMR Studies of Thermotropic Polymers
Abstract As already emphasized by some review articles, among the various techniques that are used to study polymers, NMR spectroscopy has proved to be of particular interest in the case of thermotropic polymers.l,2 The tensorial interactions such as the chemical shift anisotropy, homonuclear couplings in the case of 1H NMR, heteronuclear dipolar couplings in the case of 1 3C NMR, and quadrupolar couplings in the case of spins higher than 1/2 such as in 2H nuclei, are averaged to zero by the rapid Brownian motions of molecules in solution. However, they are not or are only partly averaged in a polymer below its glass transition or in a mesophase. Importantly, all the physical interactions listed above are orientation dependent. They may also be partly averaged by molecular motions. Therefore, measurement of their intensities provides information which can be used in the investigation of orientational phenomena, molecular dynamics and organization in the solid state. Differences in intensity of the physical interactions also result in differences in relaxation times which can be used to perform discriminatory experiments, leading to the selective observation of nuclei having some well-defined characteristics.
NMR Studies of Thermotropic Polymers
Abstract As already emphasized by some review articles, among the various techniques that are used to study polymers, NMR spectroscopy has proved to be of particular interest in the case of thermotropic polymers.l,2 The tensorial interactions such as the chemical shift anisotropy, homonuclear couplings in the case of 1H NMR, heteronuclear dipolar couplings in the case of 1 3C NMR, and quadrupolar couplings in the case of spins higher than 1/2 such as in 2H nuclei, are averaged to zero by the rapid Brownian motions of molecules in solution. However, they are not or are only partly averaged in a polymer below its glass transition or in a mesophase. Importantly, all the physical interactions listed above are orientation dependent. They may also be partly averaged by molecular motions. Therefore, measurement of their intensities provides information which can be used in the investigation of orientational phenomena, molecular dynamics and organization in the solid state. Differences in intensity of the physical interactions also result in differences in relaxation times which can be used to perform discriminatory experiments, leading to the selective observation of nuclei having some well-defined characteristics.
NMR Studies of Thermotropic Polymers
Lauprêtre, Françoise (author)
1992-01-01
39 pages
Article/Chapter (Book)
Electronic Resource
English
Thermotropic Side Chain Liquid Crystal Polymers
| Springer Verlag | 1992
Thermotropic Main Chain Liquid Crystal Polymers
| Springer Verlag | 1992
| British Library Online Contents | 1996
| British Library Online Contents | 1995