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.