## 3 Results and Discussion
### Toughening  
The most common method to enhance rigid polymers' toughness is by melt blending with elastomers or block copolymers. In addition, the toughening effect depends on the phase morphology, elastomer-block copolymer content, and interfacial adhesion, just like the evaluated properties [59,60]. As observed in Figure 8, the processing method, content of SBS, and copolymer architecture were decisive in increasing or decreasing the impact resistance of the PPE/HIPS/SBS blends. Comparing processing methods, all blends compounded by TSE (except PPE/HIPS/SBS411R-24-TSE) exhibited higher impact resistance due to superior dispersive action, see Figure 8, as mentioned before [12,37]. The impact resistance of the PPE/HIPS/SBS processed by TSE was higher for the blends prepared with SBS411R, the radial block copolymer with the highest M\({}_{\rm w}\). However, the blends made by IM, especially SBS416R with radial copolymer with medium M\({}_{\rm w}\), produced the highest impact resistance. For example, PPE/HIPS/SBS411R-18-TSE showed the highest impact resistance with 44.2 kJ m\({}^{-2}\). In contrast, the exact blend prepared by IM presented only 24.68 kJ m\({}^{-2}\). Thus, the TSE distributes the soft phase more homogeneously; consequently, the blocks of PB behaved as a more effective toughener or in situ reinforcing agent [61,62]. Nevertheless, the decrease in the impact resistance for PPE/HIPS/SBS411-24-TSE, PPE/HIPS/SBS416-24-TSE, PPE/HIPS/SBS4301L-18-TSE and PPE/HIPS/SBS4301L-24-TSE blends was due to poor miscibility between the blocks of PPE and PB as the content of SBS increased, suggesting that the increment of PB caused PS (at some concentration) not to support or be compatible with PB. Compared to PPE/HIPS/SBS blends, PPE/HIPS-40, the PPE/SBS416R-40 or PPE/SBS4301L-40 blend exhibits a negative effect on the impact resistance resulted, despite the rise at 40 wt% SBS and regardless of the architecture (radial or linear), Figure S6 [32]. Figure 8: Izod impact resistance of PPE/HIPS/SBS-X-Y-Z blends vs. PPE/HIPS-22-IM or PPE/HIPS-22-TSE: (**a**) PPE/HIPS/SBS411R-Y-TSE or IM; (**b**) PPE/HIPS/SBS416R-Y-TSE or IM; and (**c**) PPE/HIPS/SBS4301L-Y-TSE or IM. Therefore, the causes of the negative effect of the impact resistance were the lack of compatibility and poor interfacial adhesion between the two components since PB and PPE are not miscible. Moreover, PPE/HIPS/SBS411R-TSE and PPE/HIPS/SBS416R-TSE blends (except PPE/HIPS/SBS411R-24%-TSE) exhibited excellent impact resistance compared to those with the SBS linear block copolymer. Due to the presence of an extensive number of physical cross-linking sites in the radial than in the linear copolymers triggered improved mechanical properties in the ternary blends [32; 33; 34]. As known, the size and substructure of the dispersed rubber modifier play a crucial role in determining the ultimate toughening effect and the deformation mechanism [63; 64]. In addition, surface homogeneity improves impact resistance because of a similar shape, particle size, and acceptable rubber particle dispersion [65]. The evidence indicated that the IM could not distribute the SBS411R properly due to its high M\({}_{\rm w}\) and viscosity. In contrast, it was possible by TSE, which involves a significant dispersive action. Since SBS416R has a medium M\({}_{\rm w}\), IM was able to distribute it properly; therefore, it behaved as an adequate toughener by this method. The PPE/HIPS/SBS411R-24-TSE blend presented the lowest impact resistance of all the blends, including those prepared by IM. Meanwhile, for the PPE/HIPS/SBS4301L-TSE blends, the impact resistance started to diminish at 18 wt%. Despite the rise of PB in the PPE/PS matrix and the independence of the SBS architecture, a negative effect on the impact resistance arose. Thus, the compatibilization must be within the optimal range to achieve the super-toughness of a polymer blend [59; 66].