Separation of Linear Polyethylene from Isotactic, Atactic, and Syndiotactic Polypropylene by High-Temperature Adsorption Liquid Chromatography

For the first time polyolefins are separated according to tacticity by liquid chromatography. High-temperature gradient HPLC is shown to be suitable for the separation of polyethylene and polypropylene. As the stationary phase a porous carbon-based material is used; the mobile phase is composed of 1-decanol and 1,2,4-trichlorobenzene. It is shown that at an operating temperature of 160 °C linear polyethylene as well as syndiotactic and atactic polypropylenes are fully adsorbed on the stationary phase from 1-decanol. In contrast, isotactic polypropylene is fully eluted. This behavior provides a novel way for liquid chromatographic separation of polyolefins. After the isocratic elution of isotactic polypropylene with 1-decanol, all retained components are desorbed from the column packing in a gradient of 1-decanol/1,2,4-trichlorobenzene. Nearly baseline-separated peaks are obtained for all components even in the case where the components do not differ in their molar masses.