Fabrication and topochemically controlled diacetylene-based polymer and its colorimetric application toward HCl detection

The detection of highly toxic HCl fumes in a convenient, fast and reliable manner is essential due to its potential human health hazards. For this purpose, we have used polydiacetylenes (PDAs) due to their unique colorimetric transition of blue-to-red in response to various stimuli. In the present work, we prepared diynediamides (DAs) functionalized with tertiary amines bearing alkylene chains of different lengths. The colorimetric responses of various DAs in the PVC polymer matrix upon exposure to UV light and HCl gas were investigated using UV vis absorption and Raman spectroscopy. The topochemical polymerization of DA monomers was also explored using DFT calculations, and the findings fail to support the odd-even rule. Furthermore, spin coating was used because it allows the rapid and facile preparation of homogeneous thin films, and the time-dependent color transitions in the presence of HCl gas were recorded. Moreover, using an inkjet printer, a single-component ink solution containing DCDA-DMPDA was used to prepare lightweight, inexpensive and flexible sensing systems with tailored patterns. Paper based test strips embedded with poly(DCDA-DMPDA) can be used to detect HCl with lower concentrations up to 0.1 mM.