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

Herein, we report improving the electrochromic (EC) properties of metallo-supramolecular polymers (MSPs) via forming nanocomposite with a layered inorganic-imidazoline covalently bonded hybrid (LIIm). Polymer-based nanocomposites exhibit improvements in mechanical, optical, gas barrier properties, etc. Clay minerals and organoclays are beneficial additives in synthesizing nanocomposites. However, only a few investigations of their EC properties have been reported. We have prepared the nanocomposites of Ru(II)-based metallo-supramolecular polymer (polyRu) and LIIm by mixing them in various polyRu/LIIm ratios in methanol. Then, the EC properties and structural features of the resulting red nanocomposites (polyRu-LIIm composites) were analyzed. The polyRu-LIIm composites exhibited strong metal-to-ligand charge transfer (MLCT) absorptions at similar to 530 nm with a slight red shift (4-7 nm) than that of pristine polyRu. The MLCT absorptions of polyRu-LIIm composites were more intense than that of polyRu. Spin-coated polyRu-LIIm composite films showed a reversible pair of redox waves at half-wave potentials (E-1/2) of 0.9 V in cyclic voltammetry (CV) curves and reversible EC changes between red and pale green caused by the redox of Ru(II/III) upon applied potential. The E-1/2 and peak currents do not drastically change compared to those of polyRu. Furthermore, the composite thin films exhibited coloration efficiencies (CE) of 640-810 cm(2)/C higher than the 597 cm(2)/C of polyRu. The high optical contrasts (Delta T) of >70% and fast switching times were maintained. Scanning electron microscopy (SEM)-energy-dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses revealed the characteristic structural features of polyRu-LIIm composites where polyRu-coated LIIm forms agglomerate (200 nm-10 mu m), which varied with the polyRu/LIIm ratios. Furthermore, the EC memory times were improved to 26 min for one of the polyRu-LIIm composites from 170 s of polyRu.