Abstract
The infrared spectra for a series of random styrene-acrylonitrile (SAN) copolymers of various compositions were analyzed to determine the dependence of the individual spectral peaks on the copolymer composition. Correlations were established to relate changes in the peak positions and intensities to changes in the copolymer composition and monomer sequence distribution. It was found that a number of peaks shift to higher frequencies as the amount of acrylonitrile in the SAN copolymer is increased while others shift to lower frequencies. It was also found that some peak positions are unaffected by changes in the copolymer composition. The intensities of the spectral peaks were also analyzed as a function of the copolymer content by plotting changes in the intensity values against the number fraction of each of the possible monad, dyad, and triad structures. A peak was then determined to result from a given microstructure if there exists a positive linear relationship between the peak intensity and the number fraction of this microstructure.
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