Preparation of novel fluorinated highly branched (A3 + B3)-type hyperbranched poly(amide-imides) for electrochromism and iodine adsorption

In this study, a series of (A₃ + B₃)-type fluorinated hyperbranched poly(amide-imides) were successfully synthesized with carbazole and fluorene units as end-capping moieties. All synthesized end-capping hyperbranched PAIs showed over 70% branching as determined by ¹H NMR, demonstrating good solubility and thermal stability (T_gs: 242–263°C, T_10%: 576–629°C). The HOMO and LUMO energy levels of hyperbranched PAI films were measured at 4.65–4.73 and 1.51–1.66 eV, respectively, suggesting favorable reoxidation and reduction characteristics. PAI-2 demonstrates a 46.6% transmittance variation (∆T, 418 nm), along with a coloring/bleaching process time of 2.3 s/1.6 s, a coloring efficiency (CE) of 310 cm²/C, and exceptional redox stability over 100 cycles. Furthermore, the synthesized PAIs containing electron-withdrawing groups exhibited a high iodine adsorption capacity as determined by iodine adsorption tests (PAI-1: 534 mg/g, PAI-2: 579 mg/g, PAI-3: 490 mg/g).