DETERMINATION OF MICROSTRUCTURE AND COMPOSITION IN BUTADIENE AND STYRENE BUTADIENE POLYMERS BY NEAR-INFRARED SPECTROSCOPY

Transmission spectroscopy In the near-infrared region (1100-2500 nm) is used to determine the microstructure and the composition of poly(butadiene) (PBD) polymers and styrene-butadiene (SBR) copolymers in bulk and in carbon tetrachloride solution. The multivariate method of classical least squares (CLS) is used to analyze near-infrared spectra of polymers with NMR-determined microstructures and compositions. Although the near-Infrared spectra of the pure analytes (cis-1,4-butadiene, trans-1,4-butadiene, 1,2-butadiene, and styrene) are highly overlapped, the CLS method provides accurate predictions of analyte concentrations, because all available spectral frequencies are used for quantitation. The results Indicate that the near-infrared spectrum in the first-overtone CH stretching region (1570-1850 nm) can be used to predict 1,2-butadiene within 0.947% (mass), cis-1,4-butadiene within 1.03%, trans-1,4-butadiene within 1.15%, and styrene within 1.38% in PBD and SBR polymers. The second-overtone CH stretching region (1100-1350 nm) and the CH combination band region (1950-2500 nm) are also very useful. The sensitivity of near-Infrared spectroscopy to intermolecular interactions and neighboring-group effects in these polymers is demonstrated. © 1990, American Chemical Society. All rights reserved.