Fine tuning the color-transition temperature of thermoreversible polydiacetylene/zinc oxide nanocomposites: The effect of photopolymerization time

• Polydiacetylene/zinc oxide (PDA/ZnO) nanocomposites are prepared by varying photopolymerization time.
• These PDA/ZnO nanocomposites exhibit reversible thermochromism.
• Increase of photopolymerization time causes systematic decrease of color-transition temperature.
• Color-transition temperature ranges from about 40 to 85 °C.
• This simple method can provide a library of materials with controllable thermochromic behaviors.

An ability to control the thermochromic behaviors of polydiacetylene (PDA)-based materials is very important for their utilization. Recently, our group has developed the PDA/zinc oxide (ZnO) nanocomposites, which exhibit reversible thermochromism (Traiphol et al., 2011). In this study, we present our continuation work demonstrating a rather simple method for fine tuning their color-transition temperature. The PDA/ZnO nanocomposites are prepared by varying photopolymerization time, which in turn affects the length of PDA conjugated backbone. We have found that the increase of photopolymerization time from 1 to 120 min results in systematically decrease of the color-transition temperature from about 85 to 40 °C. These PDA/ZnO nanocomposites still exhibit reversible thermochromism. The PDA/ZnO nanocomposites embedded in polyvinyl alcohol films show two-step color-transition processes, the reversible blue to purple and then irreversible purple to orange. Interestingly, the increase of photopolymerization time causes an increase of the irreversible color-transition temperature. Our method is quite simple and cheap, which can provide a library of PDA-based materials with controllable color-transition temperature.

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