Mössbauer and infrared spectroscopic studies of novel mixed valence states in cobaltous ferrocyanides and ferricyanides

Novel mixed valence states have been obtained by the treatment of cobaltous ferrocyanides (Co⁺²Fe^II) and ferricyanides (Co⁺²Fe^III) in an ozone flow. The CN stretching bands occur at 2085 cm^–1 for Co⁺²Fe^II and at 2160 cm^–1 for Co⁺²Fe^III. After the ozonization process of Co⁺²Fe^II, an intense band approximately at 2125 cm^–1 is detected. This intermediate band must correspond to a mixed valence state of the type: Fe^II–CN–Co²⁺–NC–Fe^III Mössbauer spectra recorded in situ during the ozonization of Co⁺²Fe^II show the presence of two components: a doublet with isomer shift and quadrupole splitting values close to the cobalti ferricyanide and a very broad line for the mixed valence state. From the Mössbauer and infrared spectra of the aged samples of the Co⁺²Fe^II after ozonization, a relaxation process to the initial state of the samples is observed but the mixed valence state is stable.     

Infrared microspectroscopic study of the thermo-oxidative degradation of hydroxy-terminated polybutadiene/isophorone diisocyanate polyurethane rubber

Hydroxy-terminated polybutadiene/isophorone diisocyanate (HTPB/IPDI) polyurethane rubber which was aged in air at elevated temperatures has been studied by infrared microspectroscopy. Spectra were collected in transmission mode on microtomed samples. Analysis of sets of spectra taken across the sectioned material showed that most of the degradation occurred in the polybutadiene part of the polymer and that the urethane linkage was essentially unchanged. The trans isomer of the polybutadiene appears to be preferentially degraded compared with the vinyl isomer. The IR technique does not provide significant information about the cis isomer. The IR spectra indicated that likely degradation products included acids, esters, alcohols, and small amounts of other products containing a carbonyl functional group. Band area ratios, supported by a principal components analysis, were used to derive degradation profiles for the material. These profiles were steep-sided indicating an oxygen diffusion limited process.