Synthesis and electro-optical properties of aromatic polyamides and polyimides bearing pendent 3,6-dimethoxycarbazole units

• A new diamine monomer with pendent 3,6-dimethoxycarbazole group was synthesized.
• New electroactive polyamides and polyimides were prepared.
• The polymers exhibited enhanced electrochemical and electrochromic stability.
• The polymers are potential anodically coloring electrochromes.

This work deals with the synthesis and characterization of a new m-phenylenediamine-type monomer with pendent 3,6-dimethoxycarbazole group, namely N-(4-(3,6-dimethoxycarbazol-9-yl)phenyl)-3,5-diaminobenzamide (2), and its derived aromatic polyamides and polyimides. New electroactive aromatic polyamides were synthesized from diamine 2 with four aromatic dicarboxylic acids via the phosphorylation polyamidation technique, and the polyimides were prepared from equimolar mixtures of 4,4′-oxydianiline and diamine 2 with four aromatic tetracarboxylic dianhydrides via a conventional two-step procedure. All the polyamides and the 6FDA-derived polyimide were readily soluble in many organic solvents and could afford strong and flexible films by solution casting. The polymers showed useful levels of thermal stability with glass-transition temperatures (Tgs) in the range of 237–313 °C and 10% weight-loss temperatures in excess of 450 °C. All the polyamides and polyimides showed reversible electrochemical oxidation, accompanied by strong color changes. By incorporation of electron-donating methoxy groups on the electrochemically active C-3 and C-6 sites of the carbazole unit, the polymers exhibit greatly enhanced electrochemical stability and electrochromic performance in comparison with the analogs without any substituents on the carbazole unit.

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