Slow motions detection in polybutadiene through novel analyses of MSE refocusing efficiency and spin-lattice relaxation

TL;DR

This paper introduces novel NMR analysis methods to study slow relaxation motions in polybutadiene near its glass transition, revealing how MSE efficiency and relaxation times reflect alpha-process dynamics.

Contribution

It applies a new model to analyze dipolar NMR signals without the Anderson-Weiss approximation, providing insights into alpha relaxation in polymers.

Findings

MSE refocusing efficiency reveals alpha relaxation features.

Temperature dependence of spin-lattice relaxation supports the analysis.

New model captures slow motions without traditional approximations.

Abstract

Novel methods to analyze NMR signals dominated by dipolar interaction are applied to the study of slow relaxation motions in polybutadiene approaching its glass transition temperature. The analysis is based on a recently developed model where the time dependence in an ensemble of dipolar interacting spin pairs is described without resorting to the Anderson-Weiss approximation. The ability to catch relevant features of the $\alpha$ relaxation process is emphasized. In particular, it is shown that the temperature profile of the Magic Sandwich Echo efficiency carries information on the frequency profile of the $\alpha$-process. The analysis is corroborated by the temperature dependence of the spin-lattice relaxation time.