Imaging with Functional Group Maps Using Infrared Microspectroscopy

The interface of a two-dimensional computer-controlled stepper-motor-driven microscope stage with an infrared microspectroscopy system is explained in terms of its usefulness in performing microscopic imaging. Images are obtained by reducing spatially specific infrared spectra to functional group maps. The maps are constructed at a given infrared absorption frequency and are a function of the intensity versus x and y spatial coordinates. The use of the technique is demonstrated through two examples of polymer characterization. Transmittance infrared spectra reduced to five images based on absorptions at 1735, 1241, 1016 (ester functionalities), 1892 (crystalline band), and 908 (vinyl unsaturation) cm−1 show that a polyethylene film contains an inclusion of an acetate-containing material. Reflectance infrared spectra reduced to an image based on a ratio of the absorptions at 1738 cm−1 (ester carbonyl) and 1705 cm−1 (acid carbonyl) show that the streak in a film of an ethylene-acrylic acid/ethylene-methacrylate copolymer blend on aluminum foil contains more of the ester component of the blend.