Influence of crystalline and amorphous microscopic morphology on the capacitance performance and electrochromic phenomenon of triazine-based polyimides

In this paper, two series of polyimides TPI-Ns and TPI-Ds containing triazines were prepared using NMP and DMF as precursor solvents respectively. Through the characterization of XRD, FT-IR and SEM, it was found that the secondary structures of the two types of TPIs were significantly different. The former shows a higher crystallinity while the latter shows an amorphous state. The two types of polyimides were respectively prepared into gel polymer electrolytes (GPEs) and applied to capacitor devices with ITO as the electrode. It was shown that the charge–discharge rate of the two types of devices differed significantly with the concentration of TPI added in GPEs system. Compared with the former, the latter showed a stronger linear correlation, and the equation of the relationship between charge and discharge time t and TPI addition quantity c was fitted. In addition, it was found that the electrochromic device prepared with TPI-D-2 as the active layer could change the color between white, amaranth (coloring state) and green (fading state) with additional voltage (< 4.5 V) was applied. All the above indications show that the short-range ordered structure of TPIs can affect its microscopic morphology and is directly related to its capacitance performances and electrochromic activity.