Structural Colored Balloon Composed of Temperature-Responsive Polymers Showing LCST Behavior

Structural colored balloons (SCBs) consisting of polymer thin film developed structural color by thin-layer interference on the shell. Thermoresponsive SCBs were prepared with poly(diethylene glycol monomethyl ether methacrylate)- co-poly( N-phenylacrylamide), which shows lower critical solution temperature (LCST) behavior. When cooling gelatin aqueous solution in which osmotic pressure was not operated, only hydration of the copolymer progressed due to LCST transition. The optical path length of the SCB increased due to swelling by water and subsequently decreased due to dissolution. The structural color changed according to the change in optical path length. In cold pure water, in addition to the hydration, osmotic pressure was operated to induce an influx of the outer solvent and the resulting diameter change also affected the shell thickness. The structural color change was analyzed to reveal that the dissolution of the polymer had significant effect on the developed structural color.