Eur. Phys. J. B (2015) 88: 283
https://doi.org/10.1140/epjb/e2015-60417-6

Regular Article

A novel analysis for the NMR magic sandwich echo in polymers: application to the α-relaxation in polybutadiene

¹ CNR, Istituto Nanoscienze, v. Campi 213/A, 41125 Modena, Italy
² Rutherford Appleton Lab, Dept. Comp. Sci., Didcot OX11 0QX, Oxon, UK
³ Dipartimento di Fisica “A. Volta”, Università di Pavia, 27100 Pavia, Italy

^a e-mail: marco.pieruccini@nano.cnr.it

Received: 16 December 2014
Received in final form: 25 May 2015
Published online: 2 November 2015

Abstract

On the basis of a method to describe the relaxation dynamics in an ensemble of spin pairs, an analytical expression is derived for the magic sandwich echo refocusing efficiency of ¹H-NMR signals from systems where dipolar interaction dominates. At the sake of illustration the method is applied to the analysis of the α-relaxation in poly(butadiene). The Vogel-Fulcher-Tammann behaviour of the central relaxation rates, derived by fitting the refocusing efficiency as a function of the temperature, follows very well independent measurements performed with stimulated echo ²H-NMR experiments. Comparison with literature data worked out by broad band dielectric spectroscopy also shows very good agreement. In the framework of an Havriliak-Negami representation of the distribution of correlation times, information about width and asymmetry of the frequency profile is also provided by the analysis. This novel method is believed to represent a suitable path to extract basic information on the motional distribution in a variety of similar systems.