Figure 5 Mass distribution of polybutadiene considering two catalytic sites.
Comparing Figures 4 and 5, it is noted that Figure 5 presents a bimodality, while Figure 4 does not. This is expected, since the presence of two active centers with different kinetic constants generates polymer chains with different growths, which leads to the widening of the distribution and the appearance of bimodality. This bimodality can be seen in the polydispersity index, which jumped from 2 to 3.25 due to the presence of another active center. The preparation of the catalyst strongly influences the presence of the active centers, since the choice of reagents, the preparation time, the preparation method, the reaction temperature, the storage temperature and the order of the reagents determines the formation of the active centers of the catalyst .
In addition, when comparing the average molar masses of the simulation with one active centre with that with two active centres, an increase in the average molar masses is observed, mainly in the weight-average molecular weight, which greatly increases the polydispersity index. This increase is still not very significant in the general context of polybutadiene, because of that, a further simulation was carried out now with three active sites, which is shown in Figure 6.