On the theory of proton solid echo in polymer melts

TL;DR

This paper develops an improved theoretical model for proton solid echo in polymer melts, incorporating intermolecular dipole interactions, which enables insights into polymer segment dynamics over millisecond timescales.

Contribution

An enhanced theory of proton solid echo in polymer melts is formulated, accounting for intermolecular dipole-dipole interactions to better understand polymer dynamics.

Findings

Intermolecular dipole interactions influence solid echo signals.

Short-time echo build-up relates to polymer segment displacements.

Potential to probe polymer dynamics in the millisecond regime.

Abstract

Based on a modified Anderson-Weiss approximation (N. Fatkullin, A. Gubaidullin, C. Mattea, S.Stapf, J. Chem. Phys. 137 (2012), 224907) an improved theory of proton spin solid echo in polymer melts is formulated, taking into account contribution from intermolecular magnetic dipole-dipole interactions. The solid echo build-up function defined by the relation , where , and are the respective signals arising from ( ),( ) and ( ) spin echo experiments, where is an operator rotating the spin system on the angle relatively axis , is investigated. It is shown that the intermolecular part of this function at short times , where is a characteristic time for flip-flop transitions between proton spins, contains information about the relative mean squared displacements of polymer segments at different macromolecules, opening up a new opportunity for obtaining information about polymer dynamics in the millisecond regime.