Poly(N‐isopropylacrylamide) microgel‐based etalons for determining the concentration of ethanol in gasoline

A device composed of a poly (N‐isopropylacrylamide)‐based microgel layer sandwiched between two thin gold layers was used as a platform for determining the amount of ethanol in gasoline (octane number of 87). This device, also known as an etalon, has unique optical properties, which depend on the diameter of the microgels that make up the device. We show that the optical properties of the device depend on the concentration of the ethanol in gasoline samples. Specifically, as the reflectance peaks shift to higher wavelength, the visual color of the device changes from green to red up to 12% (v/v) ethanol. We show that the response was consistent from sample to sample and that the devices are reusable at least three times. We went on to show that the response did not depend on the source of the gasoline, and that the etalon's response is specific to ethanol compared to other common solvents found in gasoline. The performance of these devices make them potentially useful for detecting ethanol in gasoline at the time of gasoline purchase, to determine if the gas being purchased has been adulterated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42106.