Synthesis And Chatacterization Of Near-infrared Electrochromic Polyimide

Polyimide has a good ability to adapt to the space environment, and used onthe spacecraft widely. Anthraquinone imide possesses near infraredelectrochromic property. In this paper, we proposed the introduction ofanthraquinone imide into the side chain of polyimide. For this purpose, a diaminemonomer which contains anthraquinone imide moiety was designed andsynthesized. To prove the feasibility of synthetic route that we designed, thestructure of intermediate and monomer we synthesized was analyzed by NMR. Toexplore the monomer and polymer are controllably electrochromism, thematerials were analyzed by cyclic voltammetry and electrochemical spectrum.In the paper, we obtained ketonic acid by using phthalic anhydride ando-xylene as the starting materials in two steps, i.e., intermolecular andintramolecular Friedel-Crafts acylation. Then, anthraquinone-2,3-dicarboxylicacid was prepared through nitric acid oxidation reaction. The monomer ofdiamine was synthesized by amidation, esterification and deprotection reactions.The polyimide hanging of reactive carboxyl was synthesized by using3,5-Diaminobenzoic acid and4,4’-Oxydiphthalic anhydride. The targetpolyimide containing anthraquine imide was successfully prepared by thereaction of reactive polyimide with N-（6-hydroxyl） ethylquinone imide.The cyclic voltammetry results of the diamine monomer and its precursorshow that both of these two compounds have two reversible redox processeslocated at about-0.6V and-1.2V bias, respectively, which are corresponding tofrom radical anion and dianion of anthraquinone groups. However, a new peakemerges in the region of oxidation in the curve of diamine monomer, and theintensity of this peak gradually weakened with the number of cycle increased. Itshould be due to the reaction between two amino of the monomer. Accordingly,the cyclic voltammetry curve of the polymer material also has two reversibleoxidation-reduction processes. Further electrochemical optical curve proved thatthe reduction peak of the two potentials corresponding to the absorption bands ofnear infrared region at600-1200nm and the visible region at400-500nm. Theabsorption peak was increased with the increase of the time of bias voltage. Thisis due to the concentration of the radical anion and dianion in the solution wasincreased with the time increased.