Preparation of thin film containing thermochromic polydiacetylene vesicles

Abstract

Thermochromism properties of polydiacetylenes derived from vesicles of 10,12-pentacosadiynoic acid (PCDA) and its amide derivatives were investigated by colorimetric method using a temperature controlled UV-Vis spectrometer comparing to the color change observed by eyes. The condensation reaction of PCDA with 5 and 0.25 equivalents, ethylenediamine yielded the corresponding mono- and diamide derivatives, AEPCDA and EBPCDA, respectively. The color transition, from blue to red, of poly(PCDA) vesicles observed by eyes was 65-70 °C corresponding to 70% colorimetric response (%CR) obtained from the spectrometer. The color transition temperatures are in the order of poly(AEPCDA) < poly(PCDA) < poly(EBPCDA). The color transition of poly(EBPCDA) exhibited excellent reversibility while those of poly(PCDA) and poly(AEPCDA) were irreversible. N-(2-stearamidoethyl)pentacosa- 10,12-diynamide (SEPCDA) was also synthesized from the condensation reaction between N-(2-aminoethyl)stearamide and 10,12-pentacosadiynoyl chloride. The color transition of poly(SEPCDA) vesicles is also reversible but with less recovery of the blue color comparing to that of poly(EBPCDA). Mixing of stearic acid with PCDA during the vesicle preparation can be used to lower the transition temperature of poly(PCDA) vesicles by the maximum of 10 °C. Thermochromic films were conveniently prepared from the mixtures of polydiacetylene vesicles and aqueous solution of polymer matrixes such as polyvinyl alcohol or a polyacrylic-acrylate latex. The thermochromic properties of these films can be easily detected by eyes and the color transition temperature can be tuned by changing the types of lipid monomers or mixing of lipids that offers great potential applications in indicative labeling for varieties of temperature concerned products.