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A rutile microstructure with a novel cross-medal morphology was prepared via a hydrothermal method by using a Tantalum foil as both the doping source and the substrate. This rutile cross-medal prefers to grow along an unprecedented preferential orientation of <110> directions from the substrate, which is very different from the traditional c-axis. The new material exhibits highly enhanced field emission (FE) properties.

Flexible electrochromic supercapacitors (ECSCs) are currently under considerable investigation as potential smart energy storage components in wearable intelligent electronics. However, the lack of a suitable strategy for precisely judging its real-time energy storage status has hindered its development toward practical application. Herein, an optical-energy feedback strategy based on electrochromic contrast as a quantitative indicator of the state of charge (SOC) in flexible ECSCs has been developed using a polypyrrole (PPy)-based electrochromic electrode: carbon nanotubes (CNTs)/Au/PPy/poly­(ethylene terephthalate) (PET). A linear dependence of real-time electrochromic contrast on the SOC is established, enabling a quantitative, accurate, and on-site visualization of the energy level from digitized information. Benefiting from the inherent high color-to-color contrast in PPy during electrochromism, the strategy shows a high detection sensitivity and resolution during charging/discharging. Moreover, the good flexibility, high capacitance of the electrode, and asymmetric device design can synergistically benefit the energy storage performance of the flexible ECSC, resulting in a high energy density of 4.03 μWh cm–2 and high electrochemical stability under deformations. This work largely explores the potential and advantages of PPy for fabricating a high-performance flexible smart supercapacitor and opens up an alternative methodology for realizing a convenient, low-cost, and nondestructive SOC self-monitoring ability in flexible energy storage devices.

Abstract. Cationic, hydrophobically associating polyacrylamide (PDA) was synthesized via the inverse miniemulsion polymerization in the presence of template. Dimethyloctane(2-acrylamidopropyl)ammoniumbromide (DOAB) was synthesized via quaternization reaction and used as the hydrophobic monomer. Polyacrylic acid (PAA) was used as template for the oppositely charged DOAB. The distribution of DOAB in the inverse miniemulsion and the solution viscosity behaviors of PDA were investigated. The results showed that the complexes of DOAB and PAA were located not only at the interface of the inverse miniemulsion droplets and oil phase but also in the interior of inverse miniemulsion droplets. PDA prepared with template exhibited remarkable enhancement of solution viscosity (thickening ability). And the optimal thickening ability was obtained when the aqueous phase pH was 6.5 and the ratio of DOAB to PAA was 1. The thickening ability of PDA was improved with increasing DOAB content. PDA prepared with template showed stronger association ability than that prepared without template for its longer hydrophobic block structure, which was further supported by the plots of fluorescence spectra.

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