Separation of ethylene-norbornene copolymers using high performance liquid chromatography.

The elution behavior of ethylene-norbornene (EN) copolymers prepared with various catalysts was studied in selected binary solvent gradients using porous graphite (HypercarbTM) as stationary phase. It was found that the elution volumes of the EN copolymers correlated with their average norbornene content. For a series with norbornene content lower than 20 mol % the correlation was positive (i.e. increasing elution volumes with increasing norbornene content), whereas for a series with norbornene contents above 20 mol % it was negative (decreasing elution volumes with increasing norbornene content). It is known that EN copolymers have complicated microstructures that depend on norbornene content and the catalyst system used for synthesis. Thus, it is supposed that the opposing trends in the elution behavior of the EN copolymers are caused by differences in their microstructure, ultimately governed by the norbornene content. Our conclusions are supported by results from NMR spectroscopy, which revealed the microstructure, and differential scanning calorimetry (DSC).

Characterization of functionalized polyolefins by high-temperature two-dimensional liquid chromatography.

High-temperature two-dimensional liquid chromatography (HT 2D-LC) was developed for the separation and characterization of functional polyolefins. Therefore, the key experimental parameters, namely the injection volume, the mobile phase composition, the flow rate in SEC and the time and phase of sampling into the second dimension, were systematically varied and their influence on the resolution of separation were studied. The HPLC separation of ethylene-vinylacetate waxes was realized using silica gel as stationary phase and a solvent gradient decalin→cyclohexanone, while SEC separations were realized in the chromatographic system polystyrene divinyl benzene column/1,2,4-trichlorobenzene. By choosing suitable experimental parameters, the run time needed for one complete 2D-LC analysis of a polymer sample was shortened from about 200 min to 100 min. However, the developed method failed to adsorb polypropylene and ethylene/1-butene copolymers grafted with 13 or 3 mol.% of methyl methacrylate respectively. Using porous graphite as a stationary phase and a solvent gradient 1-decanol→1,2,4-trichlorobenzene as mobile phase 2D-LC separations of both grafted polyolefins were realized.