ATR spectroscopy applied to photochromic polymer analysis

This work reports the use of infrared spectroscopy in the Attenuated Total Reflection (ATR) mode to analyze the interactions between polymeric bases and the spiropyran. Infrared spectroscopy helps to understand the interactions between the different molecules, spiropyran polymeric base and the solvent. Polymethyl methacrylate and cellulose acetate as polymeric base and the spiropyran 1, 3, 3 trimethyl indoline-5-nitro benzopyrane were used. Thin films of different concentrations (0.25%, 0.5%, 1%, 2% and 5%) of spiropyran were deposited in each type of polymeric base. The infrared spectra show the frequencies associated with the chemical bonds of each molecule. A decrease in intensity of absorbance was observed for the C = O stretching mode of the acetate group located at 1720 cm^{- 1} and for the C = C and C = N stretching modes at 1642 cm^{- 1} associated with spiropyran. A shift in the intensity of the peaks was also observed due to solvent and polymeric base effects on the final film.