| The application of two-dimensional (2D) infrared correlation spectroscopy to the characterization of polymer blends has been studied. This work includes the application of generalized 2D infrared correlation spectroscopy using chemical (composition) and thermal perturbations, as well as the application of mechanical perturbation based 2D infrared correlation spectroscopy.; The nature of cross correlation analysis applied in generalized 2D correlation spectroscopy was first investigated. For composition-dependent studies, three kinds of polymer blends have been considered in this thesis: immiscible blends, like polystyrene (PS) and poly(methyl methacrylate) (PMMA); miscible blends with relatively weak molecular interactions, such as PS/PPO (poly(2,6-dimethyl-1,4-phenylene ether) and PS/PVME (poly(vinyl methyl ether)) blends; and miscible blends with strong molecular interactions, hydrogen bonded poly(vinyl phenol) (PVPh)/poly(methyl methacrylate) (PMMA) blends. In principle, asynchronous spectra should not be obtained from immiscible blends, but usually are, as a result of bandwidth changes, peak shifts and/or deviation from linear change between intensity and composition. Bandwidth change results in the appearance of a rotated four-leaf-clover like pattern in the asynchronous spectra. Peak shift gives rise to the formation of two bands, which are actually the splitting of the original band along the diagonal. Similar phenomena have been observed in miscible polymer blends with relatively weak molecular interactions, such as PS/PPO and PS/PVME blends. The new features found in asynchronous plots have previously been interpreted in terms of the detection of hidden bands, specific interactions and conformational changes. It is shown here that these new features correspond to maximum/minimum points or points of inflection in the difference spectra, which are used to calculate the 2D plots. They do not necessarily correspond to real infrared absorption bands at all. This conclusion is further verified by the experimental results from hydrogen bonded PVPh/PMMA blends, where the difference spectra and therefore the 2D plots are dependent on the data set used. The same types of changes were also observed in a temperature-dependent study of N-methylacetamide (NMA), a model amide to study the structure and interactions in biomacromolecules, such as polypeptides and proteins.; Finally, hydrogen bonded PVPh/PMA (poly(methyl acrylate)) blends have been studied by Dynamic Infrared Linear Dichroism (DIRLD) experiments. Because noise, interference, etc., has a strong influence on the quadrature spectra, several repeatable measurements were carried out to ensure the acquisition of reliable dynamic spectra. As in generalized 2D correlation IR spectroscopy, some new features revealed are due to band shifts. However, on a more positive note, it has been found that “free” and hydrogen bonded C=O groups respond in-phase with applied strain when the Tg of a PVPh/PMA blend is relatively high, due to the elastic response of the material. Although hydrogen bonded C=O groups still tends to respond in-phase with strain, the response of “free” C=O groups has an out-of-phase component, if the Tg of a PVPh/PMA blend is little bit higher than room temperature, where a visco-elastic response of the material is observed. When the Tg of the blend is at room temperature, the “free” C=O groups respond largely out-of-phase to strain, displaying a viscous behavior. |
