Preparative temperature rising elution fractionation of polyolefin elastomer and its chain microstructure

Polyolefin elastomer (POE) has very weak crystalline ability, consequently, applying the conventional preparative temperature-rising elution fractionation (P-TREF) to separate is challenging. Here, a unique, home-built P-TREF apparatus with an extensive range of temperatures from −80°C to 150°C is applied to first fractionate POE depending on its crystallizability. The main fractions are eluted at 0°C, 8°C, 15°C, 20°C, 25°C, 30°C, and 35°C. The corresponding weight percentages of fractions are 8.31, 13.38, 15.59, 12.05, 13.39, 17.30, and 10.53 wt%, respectively. The chain structures of fractions are further analyzed by high-temperature gel permeation chromatography (HT-GPC), ¹³C-nuclear magnetic resonance spectroscopy (¹³C-NMR), differential scanning calorimetry (DSC), and successive self-nucleation and annealing (SSA). The crystallinity of the fraction grows continually as the elution temperature rises. The 1-octene comonomer concentrations within the fractions decreases from 13.8 to 7.9 mol% when the elution temperature rises from −10°C to 40°C. These findings enable for the detailed recognition of the chain microstructure of POE resin and the extension of the TREF approach to POE resins. This lays the groundwork for fundamental studies and practical uses in industry.