Measuring compositional heterogeneity in polyolefins using size-exclusion chromatography/ fourier transform infrared spectroscopy

This chapter provides an introductory overview for using size exclusion chromatography (SEC) and on-line, Fourier transform infrared spectroscopy (FTIR) to characterize comonomer content across the molecular weight distribution in polyolefins. The basic spectral aspects of the method, considerations for FTIR as an on-line detector, and the use and limits of on-line SEC-FTIR to detect polymer compositional heterogeneity are addressed. Although on-line SEC-FTIR is a rapid and powerful tool to detect trends resulting from catalyst and process changes, the method's ability to discern a sample's compositional heterogeneity is dependent upon the extent to which the molecular weight distributions of its components overlap. In some cases, SEC-FTIR cannot fully elucidate a sample's compositional heterogeneity. Other techniques such as analytical temperature rising elution fractionation (ATREF) must then be used.