Temperature sensing using reversible thermochromic polymeric films

Temperature sensing membranes using Nafion® as the polymeric support matrix have been prepared incorporating common pH indicators and stains as visible indicators. These simple systems depend on the temperature sensitivity of the acid–base equilibria between the indicator and the acidic Nafion®. The films are able to sense temperature change through a change in film colour resulting from the equilibrium shift between different forms of the indicating dye. The dyes (phenolphthalein, methylene blue, safranin-O and crystal violet) studied covered a temperature range from 4 to 70 °C.