Two-Dimensional Correlation Vibrational Spectroscopy Study on Intermolecular Interactions in Polymer Blends

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Two-dimensional infrared, Raman, near-infrared (2D IR, 2D Raman, 2D NIR) correlation spectroscopy and hetero 2D correlation spectroscopy have been applied to the studies of the conformational changes and specific interactions in various polymer blends such as those of atactic polystyrene (PS) and poly(2,6-dimethyl-1,4-phenylene ether)(PPE), It was found that 2D vibrational correlation spectroscopy is powerful in detecting bands which are not readily identified in onedimensional spectra. The 2D synchronous correlation analysis separates the NIR bands of PS from those of PPE.The 2D asynchronous correlation analysis produces cross peaks that are indicative of the specific interaction or the conformational change in the blends. It is concluded from the 2D correlation analysis that not only the phenyl rings of PS and PPE but also the CH_3 groups of PPE play important roles in the formation of the blends.The 2D Raman-NIR heterospectral correlation spectroscopy was employed to investigate intermolecular interactions in the blends of poly(methyl methacrylate) (PMMA) and poly(4-vinyiphenol) (PVPh). Ten blends of PMMA/PVPh studied contained small PVPh contents from 1 to10 weight percentages. 2D hetero correlation spectroscopy was first applied to separate the weak vibrational bands of the minority PVPh from the strong bands of the principal PMMA, and then to detect the intermolecular interactions between PMMA and PVPh. The Raman-NIR hetero-correlation analysis detects two bands at 6764 and 4637 cm_<-1> for the hydrogen-bonded hydroxyl group of PVPh, and one band at 5052 cm_<-1> for the hydrogen-bonded carbonyl group of PMMA.All these bands are not identifiable from the one-dimensional spectra.