Determining the composition and microstructure of ethylene–propylene copolymers by pyrolysis–gas chromatography

The average composition and detailed microstructure of copolymers of ethylene and propylene have been studied by pyrolysis–gas chromatography (Py–GC), using a statistical modeling approach to analyze the data. The trimer distribution obtained from Py–GC is used to infer monomer arrangement information, which is quantified in terms of a number-average sequence length for each monomer. These values are used to define the microstructure and to calculate the average composition. Compared with other available techniques, Py–GC provides a simple, quick and reliable approach to study the microstructure and composition of polyolefin copolymers. Details of this Py–GC method are discussed, including an examination of its advantages and disadvantages, and a summary of the qualitative and quantitative analysis aspects of this approach is presented. The combination of a statistical modeling approach with Py–GC to study copolymer composition and microstructure allows one to investigate the complex problem of monomer arrangement in copolymers using a widely available analytical technique. We expect that with further advances in separation technology, especially two-dimensional gas chromatography (GC × GC), research of this type will be become increasingly accurate and reproducible in the near future.