HIGH TEMPERATURE ELUTION PEAKS IN TEMPERATURE RISING ELUTION FRACTIONATION (TREF): THE BEHAVIOR OF HIGH MOLECULAR WEIGHT SPECIES

Abstract

The effects of low molecular weight species in the analytical TREF (A-TREF) have been reported. Remarkably, no literature report, describes or even mentions, possible effects of high MW polymers on the TREF mechanism. The appearance of high temperature peaks in TREF elution has been experimentally linked to the presence of high molecular weight species in the case of high density (i.e., unbranched) polyethylene. Baseline resolved peaks or shoulders on the main peak (which main peak is presumably due to lower molecular weight fraction species) were observed with peak maxima as much as ∼10–25°C higher than baseline return of the high temperature side of the main peak. These high temperature peaks are apparently due to high molecular weight species, which undergo delayed dissolution, after melting in the presence of the diluent. These transiently “undissolved” species apparently cause irreproducible A-TREF elution curves, resulting in peaks moving along the temperature axis. These high temperature peaks were observed for a polymer having a highest molecular weight fraction of species with about 10 million molecular weight, but were not observed for another polymer having a highest molecular weight fraction of species with about 1 million molecular weight.