Described is the construction of an ultrafast electrochromic window. One electrode of this window is based on a transparent nanostructured TiO 2 (anatase) film (4.0 µm thick) supported on conducting glass (F-doped tin oxide, 10 Ω cm -2 , 0.5 µm thick) and modified by chemisorption of a monolayer of the redox chromophore bis(2-phosphonoethyl)-4,4′-bipyridinium dichloride. The other electrode is based on a transparent nanostructured SnO 2 film (3.0 µm thick) supported on conducting glass (F-doped tin oxide, 10 Ω cm -2 , 0.5 µm thick) and modified by chemisorption of a monolayer of the redox chromophore [β-(10-phenothiazyl)propoxy]phosphonic acid. The electrolyte used is LiClO 4 (0.2 mol dm -3 ) in γ-butyrolactone. The excellent performance of a 2.5 cm × 2.5 cm window over 10 000 electrochromic test cyclessswitching times (coloring and bleaching) of less than 250 ms, coloration efficiency of 270 cm 2 C -1 , steady-state currents (colored and bleached) of less than 6 µA cm -2 , and memory of greater than 600 s (time required for low end transmittance to increase by 5%)ssuggest a practical technology.

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Elastomers with excellent mechanical properties are in substantial demand for various applications, but there is always a tradeoff between their mechanical strength and stretchability. For example, partially replacing strong covalent crosslinking by weak sacrificial bonds can enhance the stretchability but also usually decreases the mechanical strength. To surmount this inherent tradeoff, a supramolecular strategy of introducing a zipper‐like sliding‐ring mechanism in a hydrogen‐bond‐crosslinked polyurethane network is proposed. A very small amount (0.5 mol%) of an external additive (pseudo[2]rotaxane crosslinker) can dramatically increase both the mechanical strength and elongation of this polyurethane network by nearly one order of magnitude. Based on the investigation of the relationship between molecular structure and mechanical properties, this enhancement is attributable to a unique molecular‐level zipper‐like ring‐sliding motion, which efficiently dissipates mechanical work in the solvent‐free network. This research not only provides a distinct and general strategy for the construction of high‐performance elastomers but also paves the way for the practical application of artificial molecular machines toward solvent‐free polyurethane networks.

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