Solid‐State Nuclear Magnetic Resonance Studies of Ions in Protective Coatings III : Sodium, Lithium, and Cesium Ions in Polyimide and Epoxy‐Polyamide Coatings

Abstract

Sodium, lithium, and cesium ions were cathodically implanted into polybutadiene coatings previously and their chemical environments were examined by solid‐state nuclear magnetic resonance (NMR) techniques.1,2 Herein, these ions were implanted into polyimide and epoxy‐polyamide coatings in order to extend earlier findings. The ions were present in two types of environments when exposed to water in the polyimide coating. The cesium ions in polyimide generally yielded two peaks in the 133Cs NMR spectrum, while two species of sodium and lithium ions were inferred from relaxation data. The majority of the ions was associated with those present in the free volume sites of the polymer, while the remainder was associated with those present in pathways (defects). The NMR data showed that lithium, sodium, and cesium ions were present as a single species when implanted into the epoxy‐polyamide coating. In all three cases, a single peak occurred in the NMR spectra and a single component exponential decay curve was determined from the spin‐spin relaxation data. The most probable location of these ions is in pathways (defects) as inferred from the relaxation data. Lithium and sodium ions associated with the carboxyl groups present in the matrix when the coatings were dried.