The Availability of Neutral Cyan, Green, Blue and Purple Colors from Simple D⁻A Type Polymers with Commercially Available Thiophene Derivatives as the Donor Units.

Lingqian Kong,Xiuping Ju,Jinsheng Zhao,Min Wang,Yan Zhang,Yu Xie

doi:10.3390/polym9120656

Lingqian Kong, Xiuping Ju + Show 4 more

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https://doi.org/10.3390/polym9120656

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Abstract

In this paper, the Stille coupling reaction was used to prepare four donor–acceptor–donor (D–A–D) type monomers. For this purpose, 2,3-bis(4-methoxyphenyl) quinoxaline was used as the acceptor unit, and thiophene derivatives (3,4-ethylenedioxythiophene, or EDOT; 3-methoxythiophene, or MOTh; 3-methylthiophene, or MTh; and thiophene, or Th) were used as the donor units. The monomers were polymerized to the corresponding polymers by the cyclic voltammetry (CV) or potentiostatic method. The band gaps and the adsorption profiles of the polymers were finely tuned with the incorporation of the different thiophene units. All four polymers have low band gaps, and switched between the colored neutral states and the highly transmissive oxidized state. We were successfully able to obtain the valuable neutral colors of cyan, green, blue, and violet for the polymers employing EDOT, MOTh, MTh, and Th as the donor unit, respectively. Furthermore, electrochromic kinetic investigations showed that all four polymers displayed excellent optical contrasts (ΔT%), fast switching times, high coloration efficiencies, and robust stabilities, indicating that these four polymers are probably promising choices for developing electrochromic devices.

Highlights

In recent years, conjugated polymers have been considered potential candidates for the active materials used in the preparation of many types of electrochromic devices, including energy-saving intelligent windows, none-emissive displays, and rearview mirrors for automobiles, as a result of their flexibility, fast color-changing speed, apparent color contrast, and tunable colors by structure modification [1,2,3]
We report on the color dependence of some (D–A–D)n type neutral coloring polymers on the molecular structure of a thiophene derivative as the D unit, and 2,3-bis(4-methoxyphenyl) quinoxaline, a simple electron acceptor unit, as the “A” unit employed
The respective monomer was dissolved in the electrolyte with a concentration of 5 mM, and the Cyclic voltammetry (CV) measurement was conducted with a sand rate of 100 mV/s, until 10 cycles of the CV were completed

Summary

Introduction

In recent years, conjugated polymers have been considered potential candidates for the active materials used in the preparation of many types of electrochromic devices, including energy-saving intelligent windows, none-emissive displays, and rearview mirrors for automobiles, as a result of their flexibility, fast color-changing speed, apparent color contrast, and tunable colors by structure modification [1,2,3]. The accessibility of cathodically coloring ECPs with complete palettes of neutral state colors is a critical factor for the fabrication of high performance display devices, which could be boosted by developing synthetic methods to explore the structure–performance relationships of the polymers [7,8]. According to the statistics within the published literature to date, most of the reported ECPs have presented red or blue colors in their neutral state. Those who have been trying to get neutral green polymers have a great interest in realizing the full color spectrum on the basis of the color-mixing theory, which is based on the RGB color spaces [11]. The neutral cyan polymers are very limited, which restrict the fine tune of the colors over the entire visible regions on the base of the CMKY color space [8,12]

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