Elution behavior of polypropylene with different tacticity

High-temperature liquid chromatography (HT-HPLC) using solvent gradients enables to separate polypropylene (PP) according to tacticity. Varying the combination of adsorption and desorption promoting solvent the three stereochemical variants iPP, aPP and sPP can be selectively retained in a HypercarbTM column. Two new desorption promoting solvents, namely 1-chloronaphtalene and 2-chlorotoluene, were tested. Among these 2-chlorotoluene was found to improve the selectivity of the separation of the atactic variant from the syndiotactic one. Linear polyethylene (PE) was retained in the column in the majority of the tested solvent/sorbent systems. Thus, several HPLC systems described in this paper enable the separation of blends consisting of PE and PP, as well as the realization of selective HPLC separations of polypropylene according to its tacticity.