Preparation of Bis-Polydiacetylene with Reversible\nThermochromism and High Sensitivity toward Pb<sup>2+</sup> Detection

The\nfabrication of stimulus-responsive polydiacetylene (PDA) materials\nwith thermochromic reversibility is highly valuable for displays,\noptoelectronic devices, and sensors. Herein, a type of bis-diacetylene\nmonomer (bis-DA) covalently linked by 1,4-phenylene diisocyanate was\nsynthesized. Owing to the strong hydrogen-bonding interactions, a\nreversible color transition can be realized for the polymerized bis-diacetylene\n(bis-PDA) film in the temperature range from 30 to 150 °C. The\nexcellent linear relationship between the colorimetric response values\nand temperature (from 90 to 150 °C) with an <i>R</i><sup>2</sup> value of 0.992 demonstrated that the as-prepared bis-PDA\nsensor can be used for the quantitative analysis of temperature. Meanwhile,\nthe bis-PDA film displayed a reversible thermochromic property upon\nexposure to 980 nm near-infrared light at a relatively high power\ndensity. In addition, hybrid PDA vesicles that consist of DA and bis-DA\nmonomers with a molar ratio of 1:1 can be utilized as sensitive, specific,\nand visual sensors for the detection of Pb<sup>2+</sup> ions, with\na satisfactory limit of detection of 0.15 μM. This work not\nonly offers a fundamental understanding of the mechanism of the thermochromic\nproperty of PDA but also may broaden the applications of PDA-based\nsensors.