New irreversible thermochromic polydiacetylenes

New diacetylenic compounds are described. These compounds are unfunctionalised, monoalcohols, diols or monoesters and present irreversible thermochromic behaviour. When heated, these diynes change colour from blue to red in temperature ranging between −50 and +75 °C depending on chain lengths. A relationship between the number of atoms and the thermochromism temperature has been highlighted. Moreover, a mechanism of this thermochromic phenomenon is demonstrated based on Raman spectroscopy, ESR and solid NMR.