Proton Multiple-Quantum NMR for the Study of Chain Dynamics and
Structural Constraints in Polymeric Soft Materials
Progr. NMR Spectrosc. 51 1-35 (2007).
Proton multiple-quantum NMR is reviewed with respect to its applications to
mobile polymer systems above the glass transition. The method provides direct
access to segmental orientations arising as a consequence of anisotropic chain
motions caused by chemical or topological constraints. In this way, semi-local
structural information on the level of single (sub)chains, as well as the chain
dynamics, becomes accessible and can be related to macroscopic properties.
Multiple-quantum NMR extends the application range of traditional transverse
relaxation methods, mainly because the structural and the dynamic information
can be reliably separated by explicit consideration of the true incoherent
relaxation of the magnetization during the experiment. As a novelty,
distributions are accessible, providing a means to critically test different
models and opening new perspectives for applications. This report emphasizes
studies of permanent networks and swollen gels, and also discusses applications
to polymer melts, grafted and confined chains, and gelling systems.