Novel polyamides with fluorene-based triphenylamine: electrofluorescence and electrochromic properties

Abstract

A series of novel polyamides with fluorene-based triphenylamine units in the backbone were prepared from a newly synthesized diamine monomer, N,N-di (4-aminophenyl)-2-amino-9,9-dimethylfluorene, and various dicarboxylic acids via phosphorylation polyamidation technique. These polyamides were amorphous and exhibited excellent solubility in many polar solvents and could be solution-cast into flexible polymer films. They possess good thermal stability with glass transition temperature in the range of 256–316 °C and 10% weight loss in excess of 500 °C in nitrogen. The dilute N-methyl-2-pyrrolidone (NMP) solutions of these polyamides showed strong UV-vis absorption bands at 334–367 nm and the polyamide derived from 1,4-cyclohexanedicarboxylic acid exhibited fluorescence maximum at 441 nm with quantum yields up to 47.1%. Furthermore, the fluorescence can be effectively switched between “on” and “off” states by applying reduction and oxidation potentials, exhibiting a high contrast ratio (I_f/I_f0) of 12.7. The polymer films showed reversible electrochemical oxidation and reduction, enabling an improved stability of electrochromic characteristics with color changing from colorless to green. The anodically electrochromic films had high coloration efficiency (up to 283 cm² C⁻¹ at 860 nm) and after over 500 cycles the polymer films still exhibited continuous cyclic stability of electrochromism.