Low-field rheo-NMR: A novel combination of NMR relaxometry with high end shear rheology

Abstract

Time-domain NMR is a well known tool for assessing the molecular dynamics in soft matter by measuring the excitation and subsequent decay of 1H nuclear magnetization. It is widely used, e.g., to quantify the composition of heterogeneous soft matter systems like semicrystalline polymers or emulsions. Further applications, known from academic research and industrial application, include measuring the moisture content in solids, the residual magnetic dipolar coupling for quantifying molecular motion in crosslinked systems, or diffusometry. We report the integration of a permanent magnet based pulsed NMR spectrometer into a modern, commercially available high-end shear rheometer. The setup allows for the first time to simultaneously conduct time-domain 1H NMR and steady shear or dynamic rheological measurements on one sample and to directly correlate the results from both, without concerns about differences in the sample history or temperature calibration. Moreover, the new in-situ combination allows the full usage of the rheometer to apply nonlinear deformation, under steady shear or large amplitude oscillatory shear, and directly measure the effect on the time evolution of the sample properties. This publication introduces the technical setup of this novel instrument combination and describes the shear induced crystallization of polyolefins to demonstrate its capabilities. Further potential applications are outlined.