Synthesis, Film-Forming, and Electronic Properties of o-Phenylenediamine Copolymers Displaying An Uncommon Tricolor

Novel electrochromic copolymers from o -phenylenediamine ( o PD) with aniline (ANi) were facilely synthesized by a chemical oxidative polymerization. The synthesis, structure, and properties of the copolymers were systematically studied by changing o PD content and polymerization temperature. The dependence of the polymerization yield at 70 °C on the o PD content is quite different from that at 17 °C, indicating that the copolymerization between the o PD and ANi comonomers varies significantly with polymerization temperature, whereas the conductivity and solubility of the copolymers obtained at 17 and 70 °C demonstrate similar dependency of the o PD content. The reactivity ratios, r o PD and r ANi, of o PD and ANi were found to be 9.70 and 2.74, respectively, implying a stronger homopolymerization tendency than copolymerization between them. The copolymers exhibit stronger formability and uniformity of the film, much higher electroactivity, and better tricolor electrochromism than o PD and ANi homopolymers. The copolymer film, containing 50 mol % o PD unit is red at −0.5 to 0 V vs SCE, turns to green at 0 to +0.6 V vs SCE, and blue at +0.6 to +1.35 V vs SCE. Possible assignments of the macromolecular structures of the copolymers in different potential ranges are proposed. The difficulty of synthesizing electrochromic o PD/ANi copolymers could be overcome to some extent by the oxidative polymerization at 70 °C. Particularly, the copolymer has an uncommon combination of strong film formability, high electroactivity, and unique tricolor electrochromism, which could not be achieved by both homopolymers themselves.