Multistable molecular chain magnet in electrospun polymer fibers

Abstract

New composite materials with multi-switchable thermochromic and vapochromic properties have been produced by the incorporation of a coordination chain {NH₄[Ni(cyclam)][Fe(CN)₆]·5H₂O}_n (cyclam = 1,4,7,11-tetraazacyclotetradecane) into the electrospun fibers of poly(ε-caprolactone) (PCL) or poly(2-vinylpyridine-co-styrene) (P2VP-PS). The embedded coordination compound is characterized by reversible metal-to-metal charge transfer, which can be triggered by changes in temperature, humidity, or pressure, and under ambient conditions, it can exist in three phases differing in color and magnetic susceptibility. However, its crystalline form is brittle and easily damaged by contact with liquid water. The composite mats combine the switchability of the coordination chain with the favorable mechanical properties of the organic polymer matrix. Most importantly, the use of the hydrophobic PCL polymer provides full protection from water damage. The morphology of the mats and the influence of the polymer matrix on the properties of the embedded compound have been studied by electron microscopy (SEM and TEM), X-ray absorption (XAS) and Raman spectroscopy, PXRD, dynamic vapor sorption (DVS), and magnetic measurements.