Construction and Molecular Understanding of an Unprecedented, Reversibly Thermochromic Bis-Polydiacetylene

A new type of bis‐PDA, in which two PDAs are linked via an intervening p‐phenylene group, is developed. The Bis‐PDA‐Ph displays exceptional thermochromic reversibility owing to the presence of unique hydrophobic interactions between alkyl chains as well as aryl moieties. The Bis‐PDA‐Ph has a well‐packed structure that causes it to display a clear blue to red colorimetric transition at elevated temperatures. To elucidate the molecular origin of the thermochromic response, a theoretical simulation of the new PDA, the results of which successfully explain the thermochromic reversibility phenomenon, is conducted. Furthermore, Bis‐PDA‐Ph‐embedded polymer fibers are used as a thermochromic sensor material. It displays excellent reversibility between 20–120 °C, which is the largest temperature range reported thus far for PDA based sensors. Finally, transient absorption spectroscopy is employed for the first time to analyze the temperature‐dependent fluorescence change of the new PDA. The Bis‐PDA‐Ph (two PDAs are linked via an intervening p‐phenylene group) displays exceptional thermochromic reversibility with a blue to red colorimetric transition at elevated temperatures. To elucidate the molecular origin of the thermochromic response, a theoretical simulation of the new PDA which explains the reversibility phenomenon, is conducted. Furthermore, Bis‐PDA‐Ph‐embedded fibers display excellent reversibility between 20–120 °C.