## 2 Results and Discussion  
### Polymerization Kinetics  
The kinetics of the polymerizations carried out in this study are shown in Figure 1. This figure describes the evolution of instantaneous (\(x_{i}\)) and global conversions (\(X\)) as a function of the relative time (\(t\)). Here, \(x_{i}\) is the fraction of added monomer up to time \(t\) that has changed into polymer; \(X\), the fraction of monomer (compared to the total amount to be added) converted to polymer at time \(t\), whereas \(t_{r}\) is the ratio of a given time \(t\) divided by the total addition time. The values of \(x_{i}\) and \(X\) as a function of \(t\), and consequently, of \(t_{r}\) were calculated by the gravimetric method and using the following equations, obtained from a simple mass balances:  
\[x_{i}(t) =\frac{w_{pol}}{tF_{0}X_{m}} \tag{1}\] \[X(t) =\frac{tF_{0}x_{i}}{M_{t}} \tag{2}\]  
where \(w_{pol}\) is the amount of polymer produced up to time \(t\), \(F_{o}\) is the organic phase dosing rate, \(X_{m}\) is the monomer concentration in the organic phase and \(M_{t}\) is the total weight of monomers to be added.  
In Figure 1 and in the following figures, (a) and (b) correspond to the results of lower and higher organic-phase dosing rate, respectively. Given that in this case toluene is an inert component, it would be also appropriated to say lower and higher monomer dosing rate or simply lower and higher dosing rate hereinafter. The behavior of the \(x_{i}\) curves in Figure 1 is that typically observed in a polymerization carried out in presence of a surfactant at contents higher than its critical micellar concentration by adding the monomer in a semicontinuous fashion to operate under monomer starved conditions [16; 17; 18]. In a typical behavior \(x_{i}\) values are relatively low during the first stages of polymerization before rising with the reaction time, attaining values higher than 90%-95% under highly monomer starved conditions. In our case it should be noted that the higher \(x_{i}\) values correspond to the polymerization carried out at the higher value of \(F_{o}\). Taking into account that the only difference between the two polymerizations is \(F_{o}\), this result contravenes the expected behavior in polymerizations performed under monomer starved conditions. In accordance with the literature the inverse relationship between \(x_{i}\) and monomer dosing rate, while maintaining unchanged the rest of variables, is the very well-known fact [16; 17; 18; 21]. When the monomer dosing rate decreases the monomer concentration inside particles decreases, which leads to a reduction in the propagation rate, resulting in a diminution in the particle volumetric growth. The result is an increase in the particle number density (\(N_{p}\)). The increase in the number of places in which the monomer consumption is carried out, that is to say, the particles, overwhelms the drop in the monomer concentration in the particles, leading to an increase in \(x_{i}\). The use of a porogen and a crosslinking agent in this study could be the origin of the unexpected relationship between \(x_{i}\) and \(F_{o}\). In the following, an explanation for this unexpected finding will be provided.