Photoacoustic infrared spectroscopy has been applied to undoped polyacetylene powders and films and the results are compared to transmission infrared spectra obtained on both types of samples. the photoacoustic technique has been found to be particularly suitable for the study of polyacetylene powders which are more sensitive to air exposure than films, due to their higher surface area. The method yields spectra whose major features are essentially identical to transmission spectra, but allows more flexibility with respect to sample thickness, size, and shape. A band near 1920 cmminus;1, also observed but not discussed in previous studies, is assigned to the presence of cumulative carbon double bonds. Bands observed near 1375 and 890 cmminus;1on films and, more prominently, on powders are assigned to the incorporation of small amounts of oxygen during preparation and handling, resulting in inadvertent doping. The large surface area of powders also results in more pronounced oxidation of the polymer backbone.
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