## 4 Conclusions  
We utilized modified the Segmental Repulsive Potential (mSRP) Dissipative Particle Dynamics (DPD) approach to simulate the phase separation coupled with hydrosilylation in binary and ternary blends. Our approach introduces the first approach to capture hydrosilylation reaction along with the phase separation of preceramic precursors on the mesoscale. Our results shows that the phase separation between polyhydromethylsiloxane (PHMS) and the vinyl-terminated polydimethylsiloxane (\(v\)-PDMS) is arrested due to the hydrosilylation reaction. We characterized the dynamics of binary PHMS/\(v\)-PDMS blends undergoing hydrosilylation and ternary blends in which a fraction of the reactive sacrificial component (\(v\)-PDMS) is replaced with the non-reactive sacrificial component. As the sacrificial non-reactive component in these ternary blends, we chose methyl-terminated PDMS (\(m\)-PDMS), polyacrylamide(PAN), and poly(methyl methacrylate) (PMMA). Our results clearly demonstrate that the morphology of the sacrificial domains in the phase-separated network can be tailored by tuning the composition, chemical nature, and the degree of polymerization of the sacrificial component. Our results show a decrease in the characteristic length scale of the sacrificial domains with either an increase in the fraction of \(v\)-PDMS chains or a decrease of the degree of polymerization of these chains. We also show that an addition of a non-reactive sacrificial component introduces facile means to control the morphology by varying the fraction, degree of polymerization, or the chemical nature of this component. In particular, a decrease in affinity between the non-reactive sacrificial component and the preceramic precursors results in a decrease in the characteristic length scale of the sacrificial phase in ternary blends. Figure 6: Ternary systems with \(f_{\rm{0-PDMS}}=0.4\), \(f_{\rm{PHMS}}=0.5\), \(N_{\rm{PHMS}}=30\), \(N_{\rm{v-PDMS}}=N_{\rm{X}}=60\), where \(X=\) PAN, PMMA, \(m\)-PDMS. (**a**) Simulation snapshots upon equilibration. All beads are shown in the top row (beads of both sacrificial components are in green); and only beads of the non-reactive component (X) are shown in the bottom row. (**b**) Equilibrium characteristic length scale, \(\bar{l}\). **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/nano12183117/s1](https://www.mdpi.com/article/10.3390/nano12183117/s1)]([https://www.mdpi.com/article/10.3390/nano12183117/s1](https://www.mdpi.com/article/10.3390/nano12183117/s1)), Table S1: Solubility parameters and molar volumes of chosen monomers; Table S2: The group molar attraction parameters; Table S3: Flory-Huggins interaction parameters \(\chi_{ij}\) (T = 25 \({}^{\circ}\)C); Table S4: Repulsion parameters \(a_{ij}\) between all the types of beads; Figure S1: Phase separation in the non-reactive blend with \(f_{\rm{v-PDMS}}=0.5\) and \(N_{\rm{v-PDMS}}=100\) (no hydrosilylation reactions); Figure S2: Comparison between characteristic length scales defined by \(l\) and \(l_{min}\) in the system shown in Figure 2 of the main text (\(f_{\rm{v-PDMS}}=0.5\) and \(N_{\rm{v-PDMS}}=100\)); Figure S3: Effects of reaction probability, \(P_{\rm{c}}\); Figure S4: Snapshots of sacrificial domains in the blends with \(N_{\rm{v-PDMS}}=60\) and various \(f_{\rm{v-PDMS}}\); Figure S5: Shifted RDFs in ternary systems corresponding to Figure 6 at equilibrium. References [52; 57; 68; 69; 70; 71; 72; 73; 74] are cited in the supplementary materials. **Author Contributions:** Conceptualization, Y.X., C.K.C., R.K.B. and O.K. ; Data curation, Y.X. ; Formal analysis, Y.X., C.K.C. and R.W. ; Funding acquisition, R.K.B. and O.K. ; Investigation, Y.X., C.K.C., R.W., R.K.B. and O.K. ; Methodology, Y.X., C.K.C. and V.P. ; Software, V.P. ; Supervision, O.K. ; Validation, Y.X. and C.K.C. ; Writing--original draft, Y.X. ; Writing--review & editing, Y.X., C.K.C., V.P., R.K.B. and O.K. All authors have read and agreed to the published version of the manuscript.