# Stabilization of Pickering Emulsions by Hairy Nanoparticles Bearing Polyanions
## 3 Results and Discussion
### Salt Concentration  
It was shown that PS@PSS has no response to pH (Table S1 and Figure S3). But the salt concentration would affect the hydrophilicity of polyelectrolytes, and then it may consequently have an effect on formation of Pickering emulsion. Thus, we prepared hexadecane/H\({}_{2}\)O Pickering emulsions under various salt concentrations. The other conditions were ultrasonic power of 150 W and ultrasonic time of 3 min.  
Figure 7 shows microscope images and droplets analysis of hexadecane/H\({}_{2}\)O Pickering emulsions stabilized by PS@PSS nanoparticles under different salt concentrations. Overall, increase in salt concentration (except 100 mM) increased the emulsion droplets from 4.7 \(\upmu\)m to 16.7 \(\upmu\)m (Figure 7b). The volume distribution of emulsion droplets was the narrowest when the salt concentration was 0.1 mM (Figure 7c). However, the amount of Pickering emulsion droplets did not change substantially as the salt concentration increased from 0.01 mM to 1 mM. Particularly, an emulsion could not be prepared when the salt concentration increased to 100 mM. Thus, the response of Pickering emulsions stabilized with PS@PSS to salt concentration was significant: the average size and volume of emulsion droplets showed an evident uptrend with the growth of salt concentration in Figure 7. However, there was no marked change in droplets amount when the salt concentration was adjusted.  
The additional salt concentration shielded the electrostatic repulsive-force between PSS polymer chains. Then PSS chains shrank and tended to get close to the PS core. Correspondingly, the chains length became shorter and the exposed area of PS core would expand. This increased PS@PSS hydrophobicity. Therefore, emulsion droplets size and volume became larger with the increase in salt concentration. Additionally, as salt concentration increased and hydrophobicity of PS@PSS increased, some PS@PSS previously anchoring in hexadecane/H\({}_{2}\)O interfaces entered the hexadecane, while a few PS@PSS in water phase at first could migrate to interfaces. Thus, we could obviously observe the change in droplets size rather than droplets amount.  
Figure 7: (**a**) Microscope images of hexadecane/H\({}_{2}\)O Pickering emulsions stabilized by PS@PSS under different salt concentrations. Here the ultrasonic power is 150 W, water:oil ratio is 1:1, and ultrasonic time is 3 min. The bar is 10 \(\upmu\)m. (**b**) Particle size distribution in number corresponding to microscope images. (**c**) Droplets volume distribution corresponding to microscope images.  
However, once the salt concentration became too high, no Pickering emulsion could be prepared, and the entire system flocculated (Figure 7a). [PERSON] et al. [38] also reported that in Pickering emulsion stabilized by clay, increasing salt concentration lead to turbid dispersions of increased viscosity. Due to the electrostatic shield effect between Na+ and PSS chains, the exposed area of the PS core increased sharply, and PS@PSS nanoparticles became much more hydrophobic. Thus, the nanoparticle migration rate from the hexadecane/water interface to hexadecane was higher than that from water phase to the hexadecane/water interface. PS@PSS in water phase could not exist stably and was flocculated in a mixture with hexadecane that was totally hydrophobic.