Measurement of the thickness of thin polymer layers by infrared frustrated total internal reflection spectroscopy

A method is proposed for determining the thickness of thin (0.1–5.0 µm) polymer layers and coatings by means of infrared frustrated total internal reflection (FTIR) spectroscopy. This method is based on an analytic expression derived for the dependence of the intensities of absorption bands in IR FTIR spectra on the thickness of a polymer layer. The method is tested on model samples consisting of a thick film of polyethylene terephthalate with a layer of different thicknesses of polystyrene deposited on it. The advantage of this method is the ability to determine the thickness of thin polymer layers deposited on bulk or opaque polymer substrates.