Non-planar polyimides with monomer containing four triphenylamines for near-infrared electrochromism and TNP detection

By using triphenylamine (TPA) with a propeller structure connected to the planar fluorene unit as monomer, three novel polyimide (PI)s were prepared through chemical imidization of N,N"-(9,9-bis(4-(diphenylamino) phenyl)-9H-fluorene-2,7-diyl)-bis(N-(4-methoxyphenyl) benzene-1,4-diamine) (TPAF-NH2) with three kinds of dianhydrides. The three dimensional configurations are designed to decrease molecular stacking rising from strong imide bond, and for faster ion transport in cavity of PIs. All the three PIs have good performance of electrochromic(EC) and sensor. With the voltage increasing from 0 to 1.2 V, the color of P2 film changes from original yellow to red to blue with the response time of only 2.3 s (colored time [t(c)]) and 2.8 s (bleached time [t(b)]). The coloring efficiency (CE) of P2 reaches 310 cm(2) C-1, with optical contrast (?T) of 54%. Especially, the electroactivity of P3 does not decrease significantly after 6000 s cycle. Additionally, there are dual-band in near-infrared (NIR) area after the PI being oxidized. P1 with photoluminescence (PL) quantum efficiency (f(PL)) of 48% can detect trinitrophenol (TNP) effectively. The novel PIs have promising prospect in NIR EC and TNP detection devices.