Determination of Ion Cluster Sizes and Cluster-to-Cluster Distances in Ionomers by Four-Pulse Double Electron Electron Resonance Spectroscopy

Abstract

Double electron-electron resonance (DEER) spectroscopy is introduced as a new tool for the characterization of mesoscopic structures in polymers. This method can characterize distance distributions between spin probes in a range between 1.5 and 8 nm and can be applied to the measurement of ion cluster sizes and intercluster distances in ionically end-capped polymers by using ionic spin probes that attach themselves to the surface of the ion clusters. The results on intercluster distances for systems based on homopolymers are in agreement with earlier results from small-angle X-ray scattering (SAXS), while the cluster sizes can be rationalized by comparison with a force field molecular model of an ion cluster. The DEER experiment could also be applied to an ionically end-capped diblock copolymer for which a SAXS measurement of the intercluster distance failed.

Determination of the Nanostructure of Polymer Materials by Electron Paramagnetic Resonance Spectroscopy

“…Among these advantages, the opportunity to precisely measure spin-spin distances up to at least 5 nm [15] and to characterize distance distributions in a range up to at least 8 nm [16,17] are particularly valuable in the development of nanomaterials as well as in the structural characterization of biopolymers. This Feature Article provides a short overview of the physics behind such measurements and explains the most commonly used experimental techniques.…”

“…[100] If all pulses in the sequence have the same length of 32 ns, r min = 1.5 nm can be assumed. Equation (16) describes a shell factorization that is a good approximation if 4pr 2 DrkG(r k ) s 1 for all r k . The condition is fulfilled for kc f 0.5 6 10 -3 m and r max = 40 nm with Dr f 0.02 nm.…”

PELDOR at S- and X-Band Frequencies and the Separation of Exchange Coupling from Dipolar Coupling

“…Both time spectra were Fourier-transformed after subtracting the background caused by instantaneous diffusion (27). For biradical 5…”

Direct Conversion of EPR Dipolar Time Evolution Data to Distance Distributions

“…Using one of these techniques and suitably functionalized nitroxide spin probes, we have recently succeeded in measuring spin-spin distance distributions between 1.8 and 8 nm (18). We could thus study how the size of and the distances between ionic clusters in block copolymer-based ionomers depend on polymer chain length (19).…”