Symmetric bis-polyacetylene linked with aromatic amides targeting medium-high temperature thermal monitoring.

Polyacetylenes (PDAs) with superior thermochromic properties serve as effective safeguards against equipment overheating and personal safety hazards. However, their responsiveness to medium-to-high temperature ranges still poses a significant challenge. In this study, a series of thermochromic bis-polyacetylenes (Bis-PDA-1, Bis-PDA-2, and Bis-PDA-3) linked with symmetric aromatic amides consisting of benzene, biphenyl and bipyridine at the center have been developed. These polymers can undergo multi-step color transitions in response to thermal stimulation ranging from 80 °C to 110 °C, and after multiple heating and cooling cycles, the samples still show reversible thermochromic characteristics. The thermochromic Bis-PDAs exhibit exceptional sensitivity with instantaneous color transitions (<1 s) at 110 °C. The temperature-dependent high-contrast chromatic variations significantly improve visual discernibility in practical applications. In particular, Bis-PDA-1 displays thermochromic behavior when heated up to 110 °C, which presents a higher color transition temperature than Bis-PDA-2 and Bis-PDA-3. This is attributed to the low steric hindrance of Bis-PDA-1 at the molecular center, which enhances the intermolecular hydrogen bonding. The Bis-PDAs designed in this work present superior practicability in the field of thermal management, which also provide a guideline for the tuning of color-transition behaviors of thermochromic materials.