Infrared spectroscopic analysis of complex polymer systems

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Abstract
A procedure has been developed for the analysis of complex polymer systems, using infrared spectroscopy. Its application to the analysis of styrene–butadiene–styrene triblock copolymers hydroxylated in the solid phase by reaction with peracetic acid is described. Twenty‐two frequencies of analytical interest were found sufficient to describe the infrared spectrum of the reacted polymer and were used to estimate the concentrations of the 12 components (functional groups) found to be present. A least‐squares solution of the Lambert‐Beer law equations was used to determine the 12 concentrations of interest. The errors associated with the regression and with the uncertainties in the determination of the absorptivities were determined using model compounds with the functional groups in approximately similar environments to those found in the polymer. With this procedure, the concentrations of the major components could be determined to within ±30%, which was sufficient to determine the effects of diffusion on the solid‐phase reaction process.