Composition Fluctuation of Reversible Interlocked Polymer Networks on Microscale: Inhomogeneity in Homogeneity

Reversibly interlocked polymer networks (RILNs) were recently developed via topological rearrangement of two cross-linked polymers containing orthogonal reversible covalent bonds. Glass transition temperature measurement and microscopic observation indicated that an interlocked structure throughout the entire material can suppress phase separation between subnetworks regardless of their miscibility, but there is no in-depth study yet about the localized distribution of the subnetworks in the RILNs. In the present work, solid-state nuclear magnetic resonance spectroscopy was employed to investigate the microstructures of specially designed but representative RILNs. It was found that the macromolecular chains from different subnetworks interlaced with each other on the molecular level, while the composition fluctuation still existed and the sample with equal contents of the two subnetworks proved to be the most uniform. The outcomes will not only help to further reveal authentic microstructures of RILNs, but also benefit in the designing of new RILNs.