Results of the Ethylene Polymerizations

The polymerizations of ethylene were performed at two different temperatures and two overall pressures (approximately 10 and 20 MPa). The polymerizations in SCCO2 start homogeneous and rapidly become heterogeneous when the polymer precipitates. In contrast to the experiments performed in SCCO2, the polymerization in dichloromethane remains homogeneous throughout the reaction. The polymers resulting from aU polymerizations are clear and transparent mbbery materials. 

Tempera- Reaction Initial Polymer ture time mass of yield (K) (h) ethylene (g) ig) (kg moL ) Mw (kg moL ) MJMn H 

4 Monitoring Reaction Rate Using SAFT-LKP and SAFT-PR 

The measured pressure-time curves have been combined with the conversion-pressure curves calculated by either the SAFT-LKP or the SAFT-PR model as described in Section 8.4.2.2 to yield the conversion as a function of time (see, e.g., Fig. 8.10 b) [9]. The shape of the conversion-versus-time curves of all polymerizations is similar. At the start of the polymerization, high conversion rates were observed which gradually decrease. The reaction rate does not become zero, which indicates that the catalyst is still active at the end of the experiment. As the volume of the polymer phase is approximately 4—8 vol% according to the SAFT model, the choice for the LKP or PR eos model to describe the supercritical phase largely determines the outcome of the calculations. 

Since the yield is a function of pressure decrease, the calculated yield based on the observed pressure decrease should in principle correspond with the observed yield. Similarly, the calculated pressure decrease using the observed yield should correspond with the observed pressure decrease. The discrepancies then give a good indication of the accuracy of the models. The calculations are summarized in Table 8.9 and Fig. 8.10. The deviations in the model calculations of run El and E3 (relatively high pressure) are very small for the SAFT-LKP model. The SAFT-PR model, however, shows a significant deviation. This is consistent with the deviation in density as a function of pressure for pure components for the PR eos [9]. 

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Racemic, meso, and Cx symmetric divalent organolanthanide complexes can be synthesized by allowing the dipotassium salt of the corresponding ligand to react with Sml2 [51]. Figure 20 shows their structures determined by 1H NMR and X-ray analyses. Table 8 shows the results of the ethylene polymerization with divalent samarium complexes. It is seen that the meso type complex has the... 

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