Polydiaceylene containing amide groups and their chromism properties

Abstract

Amidodiacetylene lipids are prepared from the condensation of 10, 12-pentacosadiynoic acid (PCDA) and diamine compounds in the presence of 1-ethyl-3-(3́-dimethylamino)carbodiimide hydrochloride salt as a coupling reagent. The monoamindodiacetylenes are obtained in moderate yields (47-55 % yield) when using excess amount of diamines. Using the similar reaction with two equivalents of PCDA, the diamidodiacetylene derivatives are obtained in good yields (52-75% yield). The synthesized amidodiacetylene lipids can be dispersed in water by ultrasonication, giving translucent sol. Upon exposure with UV light, the dispersed lipids undergo photopolymerization to generate the desired blue polydiacetylenes (PDAs). The thermochromic properties of the PDAs are observed by UV-Vis spectrometer and photograph recorder. The observation reveals the structural dependence of the color transition temperatures and their reversibility. The PDAs prepared from diamidodiacetylenes with either aromatic ring or aliphatic chain linkers exhibit complete reversibility of the blue-red color transition while those prepared from the corresponding monoamido derivatives display only partial or no reversibility. The diamidodiacetylenes also gave PDAs with higher color transition temperature (70-95 oC) comparing to the monoamido analogues (65-75 oC). The thermochromism of PDAs having cyclohexyl or bis(propylenoxide ethylenoxide) as linkers between the diamide groups is virtually irreversible and has low color transition temperature (25-60 oC). The results suggest that at least two well-developed hydrogen bonds from amide groups are required for complete thermochromic reversibility. This thesis provides useful structural design for controlling color reversibility and tuning color transition temperature of PDAs.