(699d) Chromogenic Vapor Sensors Enabled By Novel Shape Memory Polymers

Here we report a new type of chromogenic vapor sensor that exhibits an abrupt change from a transparent color to a striking iridescent color when exposed to a large variety of organic vapors, such as acetone, ethanol, and toluene. Importantly, these chromogenic vapor sensors enable the specific detection of different vapors – i.e., different vapors can trigger different colors which can be distinguished by our naked eyes or by using a conventional smart phone. They can also be reused for hundreds of times with no apparent degradation in their chromogenic performance. These smart sensors integrate scientific principles drawn from two disparate fields that do not typically intersect - the fast-growing shape memory polymer (SMP) and photonic crystal technologies. Shape memory polymers can memorize and recover their permanent shape in response to an external stimulus, such as heat, light, and solvent, while photonic crystals can control the flow of light in miniature volume. The striking chrmogenic effect (from transparent to iridescent) is induced by a disorder-order transition of the macroporous SMP photonic crystals. These reusable and inexpensive chromogenic vapor sensors that show easily perceived color changes are useful for environmental monitoring (e.g., monitoring toxic vapors in buildings), homeland security (such as detecting explosives), and healthcare screening (e.g., breath testing the aount of acetone for diabetes screening).