The synthesis of a novel class of diacetylene lipid monomers containing amido or carboxyl head groups with various length methylene spacer (n = 2,3,4) between carbonyl group was accomplished by condensation of 10,12-pentacosadiynamine with various diacids or their cyclic anhydride derivatives. The polymerization and chromic properties of the synthesized polydiacetylenes (PDAs) were investigated. The monomers turned into blue or purple colors in solid state while instantaneously turned colored with different blue shade in film state depending on the alkyl chain length between carbonyl groups indicating the formation of PDAs. After diacetylene lipid monomers were sonicated in various pH of water, they can be dispersed and polymerized by 254 nm UV-irradiation to PDA sols. Thermochromic property of these PDA sols was monitored by UV-vis spectroscopy. For PDA possessing single amide head group, the low n value exhibits the lower transition temperature while PDA having two amide head groups presents the inverse tendency. On the other hand, the increasing of n value enhances the degree of reversibility of one amide PDA. Again, two amide series illustrated the opposite tendency. Fabrication of the PDAs for paper-based colorimetric sensors for 14 organic solvents and 9 types of surfactants were also achieved. As the results, sensors for 11 organic solvents and cationic surfactants by using the statistical discriminating method (Principal component analysis, PCA) were successfully developed for such detection.
