FT-IR Studies of Ionomers
Perhaps the most widely accepted model of ionomer superstructure is the multiplet-cluster concept advanced by Eisenberg [1,2]. This framework has dominated the interpretation of many vibrational spectroscopic studies to the extent that specific infrared bands and Raman lines have been separately assigned to multiplets or clusters. We were no exception to this general rule and our initial FT-IR studies of the sodium and calcium salts of ethylene-methacrylic acid copolymers were interpreted in terms of Eisenburg’s model [3,4]. Specific sharp bands in the spectra of quenched films or films held at elevated temperatures (in the range 70 to 130°C) were assigned to multiplets. Broad bands observed upon annealing these films for extended periods of time at room temperature were assigned to clusters. However, as a result of subsequent work on the salts of other group I and group II elements, we were forced to reevaluate these somewhat simplistic initial assignments . In addition, even trace amounts of water can be shown to have a profound effect on the spectrum . Because our publications in this field are, in effect, a series of successively modified interpretations, we will take this opportunity to present an overview of our work, with emphasis on the sensitivity of infrared spectroscopy to the local order found in these systems.
KeywordsCoordination Number Carboxylate Anion Calcium Salt Symmetry Analysis Zinc Cation
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