Transmission spectra polystyrene film

Figure 20-29 Fourier transform infrared spectrum of polystyrene film. The Fourier transform of the background interferogram gives a spectrum determined by the source intensity, beamsplitter efficiency, detector response, and absorption by traces of H20 and C02 in the atmosphere. The sample compartment is purged with dry N2 to reduce the levels of H20 and C02. The transform of the sample interferogram is a measure of all the instrumental factors, plus absorption by the sample. The transmission spectrum is obtained by dividing the sample transform by the background transform.

Figure 2.4 Example of the processes involved in producing an FT-IR transmission spectrum from a matt polystyrene film. FFT, fast Fourier transform algorithm. Reproduced by permission of The Royal Society of Chemistry from Industrial Analysis with Vibrational Spectroscopy, J. M. Chalmers G. Dent (1997).

To demonstrate the usefulness of the ATR method for measuring infrared spectra from hard materials, the ATR spectrum in absorbance of a pellet of polystyrene is shown in Figure 13.11a, and compared with the absorbance spectrum recorded in transmission from a thin polystyrene film shown in Figure 13.11b. The film was formed from the pellet by using a hot compression molding press. Comparison of these two spectra clearly indicates that the relative intensities of bands toward higher wavenumbers in the ATR spectrum are weaker than those in the transmission spectrum, and conversely the relative... 

Figure 15.9 Absorbance spectrum of a thin polystyrene film at30°C recorded using a transmission measurement.

Figure 12 (A) A 3.1 x 3.1 pm shear force image of a thin polystyrene film deposited on a glass cover slip. The full-scale z-range is 62 nm. (B) Near-field IR transmission spectrum of a thin polystyrene film in the aromatic C-H stretching region. The inset is the laser output over the same spectral range in the absence of polystyrene absorption. Reproduced with permission of Stran-ick SJ, Richter LJ, Cavanagh RR and Michaels C, unpublished results.

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