Two-dimensional Fourier-transform Raman and near-infrared correlation spectroscopy studies of poly (methyl methacrylate) blends 1. Immiscible blends of poly(methyl methacrylate) and atactic polystyrene

Fourier-transform (FT) Raman and near infrared (NIR) spectra have been measured for poly(methyl methacrylate) (PMMA) and its immiscible blends with atactic polystyrene (PS) of small PS contents from 1 to 10 wt.%. Generalized two-dimensional (2D) correlation spectroscopy has been applied to analyze the composition-dependent FT-Raman and NIR spectral variations of the immiscible blends, The synchronous 2D FT-Raman correlation analysis separates the Raman bans of the minority PS from those due to the majority PMMA. It detects the bands due to PS at 2900, 2856, 1562, 1494, 1201, 1184, 1156, 1130, 1097, 1069, 964, 903, 796, and 759 cm(-1), which are too weak to be observable from the one-dimensional blend spectra. The synchronous 2D Raman-NIR hetero-correlation analysis further separates NIR bands of PS from those of PMMA. It detects the bands at 6082, 5972, 5937, 5920, 4834, and 4663 cm(-1) due to PS, which are virtually unidentifiable from the one-dimensional blend spectra. These results are further proved by the synchronous 2D NIR correlation analysis. (C) 2000 Elsevier Science B.V. All rights reserved.