Synthesis, optical and electrochemical properties of new hyperbranched poly(triphenylamine amide)s

A new triphenylamine-containing AB2 type monomer with one carboxylic acid and two amino groups, 4-(bis(4-aminophenyl)amino)benzoic acid (3), was synthesized and used for the preparation of hyperbranched poly(triphenylamine amide)s. The self-polycondensation of the AB2 monomer (3) afforded hyperbranched poly(triphenylamine amide) with amino end groups. The molecular weight of the hyperbranched poly(triphenylamine amide) was 21,000 Da determined by light scattering. End-capped hyperbranched polyamides were isolated by the chemical modification of unreacted amino groups with various acid chlorides. All the hyperbranched poly(triphenylamine amide)s exhibit excellent solubility in organic solvents such as NMP, DMF, DMSO, and DMAc at room temperature. The viscosities of hyperbranched poly(triphenylamine amide)s are as low as about 0.15 dL/g due to their dendritic structures. Poly(triphenylamine amide)s end-capped with rigid benzene ring have higher thermal stability than those with amino or aliphatic end groups. The photoluminescence of the hyperbranched polyamides is blue-yellow emissions around 430–510 nm. The energy gaps of the hyperbranched poly(triphenylamine amide)s with different end groups are about 2.93 eV and are independent on the end groups, but the HOMO and LUMO energy levels are dependent on the end groups.