Analysis methodAnalytical method for determination of microstructures of solution styrene-butadiene copolymers using 2-phenylpropene/styrene ratio of pyrolysis products

Raw and cured solution styrene-butadiene rubbers (S-SBRs) with different microstructures were pyrolyzed and the pyrolysis products were analyzed using gas chromatography/mass spectrometry. 2-Phenylpropene (2-PP) was newly found to be formed from butadiene-styrene heterosequence. Formations of 2-PP and styrene were competitive and their relative intensities varied depending on the microstructure. Intensity ratios of 2-PP/styrene were plotted as a function of the 1,2-unit, 1,4-unit and styrene contents in order to employ the 2-PP/styrene plots as calibration curves to determine microstructure of unknown S-SBR samples. The 2-PP/styrene plot as a function of the 1,2-unit content had better correlation coefficients than those of the styrene and 1,4-unit contents. Correlation coefficients of the 2-PP/styrene plots were improved by correction with the 1,2-unit mole fraction. Microstructures (1,2-unit, 1,4-unit, and styrene contents) of unknown S-SBR samples could be determined using the 2-PP/styrene calibration curves.