## 4 Discussion
### Size of the Microspheres Function of Monomer Type for the Same NP-Gly  
We have investigated the role of the monomer on the size of polymer microspheres obtained by Pickering emulsion polymerization, by keeping the ultrasonication time constant and utilizing the same nanoparticle (NP-Gly). In this case, the variables that change are: (i) the thickness of the monomer/water interface dictated by the solubility of the monomer in water and (ii) the immersion depth of the NP-Gly into the polymer. By plotting the microsphere size distribution of PMM, PBM, and PtBA, Figures 4, S11 and S12, we find that the average microsphere size increases in the order PMM < PBM < PtBA, while we utilize the same NP-Gly in the Pickering emulsion stabilization of MM, BM, and tBA, see Figure 4. The size distribution for PMM microspheres is bimodal, one band with a maximum at ca. 40 \(\upmu\)m and a second one with the maximum at ca. 100 \(\upmu\)m. One possible explanation for the presence of a bimodal distribution only for PMM microspheres is that MM monomer has the highest solubility (7.4 g/L) compared to the other monomers, BM (0.4 g/L) or tBA (1.5 g/L). We hypothesize that during polymerization, the MM monomers dissolved in water could re-absorb into the polymerizing emulsion droplet and consequently generate larger microspheres. This hypothesis is supported in part by the fact that with increase in ultrasonication time, the population of the second band in the bimodal distribution increases, see Figure S9, and its maximum shifts to lower values. Because the position of the first band in the bimodal size distribution for PMM microspheres, with its maximum at 40 \(\upmu\)m, does not shift with the ultrasonication time, we take these as the representative maximum size of the microspheres resulting from the originally formed emulsion droplets stabilized by the NPs. Further, we also observe in Table 3 that the work of adhesion of NP-Gly decreases in the order PMM > PBM > PtBA, which suggests that there is an inverse relationship between the work of adhesion of NPs to the polymer vs. the size of the obtained microspheres.  
At the same time, the difference \(\Delta W\) between the work of adhesion of NPs minus the work of adhesion of NPs to the polymer:  
\[\Delta W=W_{NP/water}^{ adhesion}-W_{NP/P}^{ adhesion} \tag{5}\]  
increases in the order PMM < PBM < PtBA, which suggests a directly proportional relationship with the microsphere size. The calculated values for \(\Delta W\) are given in Table S4.  
As we already alluded above, the immersion depth of the NPs into the polymer is an expression of the affinity of the NP-Gly to the monomer and this is quantitatively expressed by the contact angle of the NPs at the three-phase line, and \(\beta\) with the monomer, which is preserved for the polymer, after the emulsion polymerization. Thus, the contact angle can be experimentally determined from the diameter of the traces left by the NPs on the colloidosome surfaces, and the found values for the NPs with the three polymers PMM, PBM, and PtBA are summarized in Table 4. From the data, the highest contact angle \(\beta\), means that the nanoparticles are least immersed in that polymer, and it appears that they generate the largest oil/water (and after polymerization polymer/water) curvature. To summarize, the experimental data show that there is a relationship of direct proportionality between the magnitude of the contact angle \(\beta\) and the difference in the work of adhesion \(\Delta W\) with the microsphere size.