Tuning of Thermochromic Properties of Polydiacetylene toward Universal Temperature Sensing Materials through Amido Hydrogen Bonding

Mono- and diamides derivatives of 10,12-pentacosadiynoic acid (PCDA) were synthesized from condensation of PCDA with various aliphatic and aromatic diamines. Polydiacetylenes of the amido-PCDA derivatives were prepared by photopolymerization of their molecular assembly homogeneously dispersed in aqueous media. Thermochromic properties of the resulting polydiacetylene sol were studied by temperature variable UV−vis spectrometry along with photographic recording. The color transition temperatures and thermochromic reversibility of the polymers are varied depended on the number of amide groups and the structure of the aliphatic and aromatic linkers. The phenylenediamide and polymethylenediamide PCDA derivatives give polydiacetylenes with complete thermochromic reversibility, while the polydiacetylenes obtained from 1,2-cyclohexylene and glycolic chain diamide derivatives exhibited irreversible thermochromism, whereas the polymers attained from the aromatic monoamide analogues are partially reversible. The variation of the linkers also allows the color transition temperature of the polydiacetylene to be tuned in the range of 20 °C to over 90 °C. The results provide a fundamental idea about the factors affecting the thermochromic properties of polydiacetylenes toward the development of materials for universal thermal indicators.