Working Mechanism of IHMEG (IMAGE)
Caption
The underlying mechanism of IHMEG. 2D-FTIR correlation spectra in the 3700–3000 cm−1 wavenumber region: a) synchronous; b) asynchronous contour maps for IHMEG samples when exposing in the air. The pink area and blue area denote the positive and negative correlation peaks, respectively. c) The water diffusion difference between the top and the bottom surface of hydrogel by 2D Raman mapping after 120 min. d) Photos of the experiment for visualizing the dynamic change of the moisture-induced ionic diffusion process. A piece of the hydrogel is sandwiched between the open ends of two cylindrical containers, the upper tube has two open ends and the bottom one has one open end and one closed end. They are filled with bromophenol blue/isopropanol solution. Water is added into the upper tube through the open end. The color change in the two tubes indicates the dynamic diffusion of dissociated protons with water diffusion. e) Schematic plot of the setup for the Kelvin probe force microscope (KPFM) test and f) the potential change of hydrogel. A piece of hydrogel (250 μm thickness) absorbed moisture from one side and the other side was covered without wetting. The potentials of the two sides are detected by KPFM. The scan range is 5 × 5 μm. The lower right picture shows the potential increment of the hydrogel after water diffusion from the wetting side to non-wetting side from 15 to 30 min. g) The proposed mechanism of moisture-induced ionic diffusion process.
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