Synthesis and unexpected electrochemical behavior of the triphenylamine‐based aramids with ortho‐ and para‐trimethyl‐protective substituents

Two series of new organosoluble polyamides with methyl‐substituted triphenylamine (MeTPA) units showing anodically electrochromic characteristic were prepared from the phosphorylation polyamidation reaction of two diamine monomers, 4,4′‐diamino‐2″,4″,6″‐trimethyltriphenylamine (Me₃TPA‐diamine; 2 ) and 4,4′‐diamino‐4″‐methyltriphenylamine (MeTPA‐diamine; 2 ′), with various dicarboxylic acids, respectively. These polymers were readily soluble in many polar solvents and showed useful levels of thermal stability associated with relatively high glass‐transition temperatures (T_g) (314–329 °C) and high char yields (higher than 62% at 800 °C in nitrogen). In addition, the polymer films showed reversible electrochemical oxidation, high coloration efficiency (CE), low switching time, and anodic green electrochromic behavior. The unexpected electrochemical behavior of higher oxidation potential and lower electrochemical stability of Me₃TPA‐polyamides I than MeTPA corresponding polymers could be attributed to the higher steric hindrance of ortho‐substituents in Me₃TPA moieties, thus made the resonance stabilization of cation radical much more difficult for the Me₃‐substituted phenyl ring. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010