Novel D-A-D conjugated polymers based on tetraphenylethylene monomer for electrochromism

Abstract A monomer (E)-4′,4‴-(1,2-diphenylethene-1,2-diyl)bis([1,1′-biphenyl]-4-carbaldehyde) (DDBC) with AIE properties and two novel DDBC-basing polyazomethines (coded as P1 and P2) were prepared. They were gained in short time, low cost and mild reaction conditions by a straightforward synthetic path. Fluorescent testing shows that DDBC owns an intense aggregation-induced emission (AIE) characteristics. But unfortunately, the polymers based on DDBC do not have AIE effect. It may be attributed that the molecules in the excited state consume light energy in the form of electron transfer, reducing the proportion of energy outputted from light, thus causing the disappearance of macroscopic fluorescence. Another guess is that the tetraphenylethylene (TPE) unit takes part of the conjugated backbone of the polymer. However, P1 have high coloration efficiency (346.94 cm2 C−1) and P2 have short response time (the color switching time is 3.43 s and the bleaching time is 1.41 s at 470 nm). Moreover, P1 has electrochromic properties in the near-infrared field. Thus, these features demonstrate that these two novel polymers have great potential as electrochromic materials in optoelectronics applications.