Monitoring time and temperature by methylene blue containing polyacrylate film

The redox characteristic of methylene blue in polyacrylate film has been investigated for applications in monitoring time and temperature. This monitoring capability is based on a color change from colorless to blue under exposure to air. The oxidation process is controlled by the air diffusion which is affected by the chemical structure of the polyacrylate. The activation energy of diffusion, which was calculated by Arrhenius equation, goes up with increasing the rigid structure of the polyacrylate. The results correlate well with the glass transition temperature of different polyacrylates. The unique feature of the methylene blue to change color under oxidation, can be used for the fabrication of low cost visual sensors for monitoring time and temperature.