Nanocomposites of Fe(II)-Based Metallo-Supramolecular Polymer and a Layered Inorganic–Organic Hybrid for Improved Electrochromic Materials

Abstract

Fe-based metallo-supramolecular polymer (polyFe), composed of Fe(II) ions and bis(terpyridyl)benzene, is known as a good electrochromic (EC) material. For the first time, to improve the EC properties, we prepared nanocomposites comprising polyFe and a layered inorganic–imidazoline covalently bonded hybrid (LIIm) by simply mixing them in methanol and then examined the effect of the nanocomposition on EC properties. The obtained blue/purple-colored composites (polyFe/LIIm composites) were demonstrated by scanning electron microscopy (SEM) to comprise a structure of LIIm nanoparticles coated with amorphous polyFe. Interestingly, X-ray diffraction (XRD) measurements suggested that there was no intercalation of polyFe in the interlayer space of LIIm. Ultraviolet-visible (UV-vis) spectroscopy measurements demonstrated that light absorption close to 600 nm was attributed to metal-to-ligand charge transfer (MLCT) from the Fe(II) ion to the bisterpyridine ligand and was influenced by LIIm in the composites. The composites exhibited a pair of redox waves, assigned to the redox between Fe(II) and Fe(III), in the cyclic voltammograms; moreover, the composites were estimated to be diffusion controlled. Thin composite films demonstrated reversible EC changes, triggered by the redox reaction of the metal. Furthermore, the results show that the nano-scale composition of the metallo-supramolecular polymers with LIIm can effectively improve the memory properties without reducing the contrast in transmittance (ΔT) of 70–76% in EC changes after applying 1.2 V vs. Ag/Ag+. The EC properties varied with varying ratios (3/0.1, 0.5, 1, and 5) of the polyFe/LIIm, and the ratio of 3/1 exhibited the longest memory and largest MLCT absorption peak among composites. The results show that the polyFe/LIIm composites are useful EC materials for dimming glass applications, such as smart windows.

Electrochromic Ru-Based Metallo-Supramolecular Polymer with a Layered Inorganic−Organic Hybrid Nanocomposite for Improved Electrochemical Properties

“…The π–π* transition absorption peaks shifted only ±1 nm. The red shifts in the MLCT were smaller for polyRu – LIIm composites than that for the previously reported polyFe – LIIm composites (up to 15 nm) in comparison with each pristine polymer . The red shifts suggest that the MLCT bandgap energy of polyRu decreased by adding LIIm .…”

“…Considerable efforts have been made for preparing polymer composites via adding inorganic materials because the composites have been expected to exhibit improvements in the mechanical, thermostable, optical, gas barrier properties, etc. of the polymeric materials. − Clay minerals and organoclays have been mixed as additives with polymers, such as polyamide, polypropylene, − polystyrene, , polyimide, polylactate, , and polyfluorene, to synthesize polymer–clay nanocomposites. − Organoclays are intercalation compounds comprising clay minerals and organic molecules, such as alkylammoniums, which are immobilized within the interlayer space of the clay minerals and are expected to exhibit good miscibility with polymers. The polymer–clay nanocomposites have been synthesized via intercalating ,, polymers into the interlayer space or polymerizing the intercalated monomers within the interlayer space of the layered materials, i.e., clay minerals and organoclays. ,, Furthermore, the layered materials are reported to exfoliate in some of the polymer–clay nanocomposites.…”

“…have been improved for the composites of polyFe covering a layered inorganic-imidazoline covalently bonded hybrid ( LIIm , Scheme ). These previous investigations led us to speculate that the composites of the EC polymers covering the additives (inorganic and inorganic–organic hybrid materials) will exhibit improved EC properties while maintaining high Δ T . Because the structures and compositions affect the properties of materials, controlling them is important to improve the targeted properties without decreasing other important properties.…”

“…The red shifts in the MLCT were smaller for polyRu− LIIm composites than that for the previously reported polyFe−LIIm composites (up to 15 nm) in comparison with each pristine polymer. 21 The red shifts suggest that the MLCT bandgap energy of polyRu decreased by adding LIIm. Previous studies have also reported red shifts for organic dyes and complexes immobilized on solid 49 and dense solutions, wherein they associated red shifts to structural changes, mobility restriction, and stabilization by the surrounding solids similar to that of solvation.…”

“…Some polymer–clay nanocomposites have been investigated as EC polymers, such as poly(3,4-ethylenedioxythiophen) (PEDOT), polyaniline (PANI), and MSPs, with layered and tubular ,, clay minerals and organoclays to improve EC properties. − The EC materials have become interesting as important materials of electrochemically tinted glasses, i.e., smart windows and antiglare rearview mirrors in cars, EC energy storage systems, and thermal management systems. ,,,,− …”