Temperature rising elution fractionation (TREF) is a characterization technique widely used to estimate chemical composition distribution (CCD) of semicrystalline copolymers. Although several mathematical models have been previously proposed to elucidate the TREF fractionation mechanism, all previous TREF models assume equilibrium fractionation; thus, they cannot describe important kinetics effects observed in TREF experiments. In this work, a new TREF model is developed incorporating crystallization and dissolution kinetic models during the fractionation process. The proposed model describes the effects of molecular weight, comonomer content, cooling rate, heating rate, and solvent flow rate on experimental TREF profiles for both polyethylene and ethylene/1‐olefin copolymers very well.

Summary Linear olefin block copolymers (OBCs) have statistical multi‐block structures and exhibit unique properties that are different from those of other polyolefin elastomers. In this work, the microstructure details of OBCs were investigated using a Monte Carlo model. Theoretical TREF profiles for these materials were simulated using a modified version of the TREF model previously developed in our group. Effects of polymerization parameters on OBC microstructures and TREF profiles were investigated. Distinctions among chemical composition distribution, longest ethylene sequence distribution, and TREF profiles were observed and discussed.