Naphthalenediimide bridged D-A polymers: Design, synthesis and electrochromic properties

We have synthesized two new D-A electrochromic polymers; poly(N,N’-bis(2-hexyl)-2,6-dithiophene-1,4,5,8-naphthalenediimide) (PTNDI) and poly(N,N’-bis(2-hexyl)-2,6-(3,4-ethylenedioxythiophene)-1,4,5,8-naphthalenedimiide) (PENDI) bearing a naphthalenedimiide chromophore in the backbone. Structural characterization of initial compounds and products were carried out by using FT-IR and 1H-NMR spectroscopies. The optical and electrochemical properties of these polymers were investigated by UV-Vis absorption spectroscopy and cyclic voltammetry, respectively. The results of spectroelectrochemical studies indicate that both polymers reveal various colors due to ambipolar redox behavior at cathodic and anodic regime. Both polymer films have reasonable redox stability (in the range of 75-80% after 1000 cycles), coloration efficiency (in the range of 80-100 cm2 C−1), and response time (approx. 1s). Moreover, it is clearly seen that replacing donor unit from thiophene to EDOT results in change only in neutral state color.

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