A soluble electron conjugated polymer for fast electrochromism and exceptional metal ion detection

The design of soluble electrochromic materials with fast responsivity for use in flexible displays and electronic papers remains a challenge. Most of the materials explored properties such as excellent contrast and rich color variation, while fast responsivity is also one of the key properties, which together push electrochromic materials into everyday life. Here we report a soluble electron conjugated polymer PDT-BTz, i.e., poly[3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1], [4]dioxepine-alt-(2-(heptan-3-yl)benzo[d]thiazole], which was designed to be highly redox active polymeric backbone for electrochromism and constructed to engineer with chelating sites for metal ion detection, via direct (hetero)arylation polymerization of 3, 4-propenyldioxythiophene with benzothiazole derivative. The resultant PDT-BTz exhibited a pair of distinct redox peaks in the range of 0.41–––1.20 V, corresponding to a clear color change in the visible region between yellow and light green as revealed by cyclic voltammetry. PDT-BTz is easily casted into thin film and is highly responsive to visible light to achieve a very short response time of only 0.21 s, which is much far superior to other polymers reported so far. Remarkably, this electrochromic PDT-BTz is highly luminescent and enables to selectively detect iron Fe (III) and Ru (III) ions, via built-in C–S and C = N chelating units, with exceptional rate constants and detection limits. Together with the high thermal stability, the electron polymer opens a way to a novel class of soluble conjugated polymer that can merge dual functions of electrochromism with ion detection capability into one material.