We use three-dimensional dissipative particle dynamics to study binary fluids undergoing the reversible reaction $A\rightleftharpoons B$ concurrent with phase separation. The interplay between reaction-induced mixing and interfacial segregation drives the system into nonequilibrium steady states with finite domains. Symmetric reaction rates ($k^f=k^b$) lead to a steady domain size $R\left(t\right)$, while asymmetric rates induce a crossover from bicontinuous networks to droplet morphologies and then saturation in the asymptotic limit. We characterize these domains using correlation functions and growth laws, $R\left(t\right)\sim t^{\theta }$, where $\theta \simeq 1$ and $2/3$ indicate hydrodynamic growth. Growth saturates at a domain size $R_s\sim k^{-\alpha }$ with $\alpha \simeq 1/3$, consistent with scaling predictions and prior studies of reaction-controlled coarsening. Thus, the chemical reaction acts as a competing relaxation channel that gradually shifts the system off criticality, regulates coarsening pathways, and ultimately arrests coarsening.

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• Chemical reactions
• Dynamics of phase separation
• Microphase separation
• Phase separation
• Spinodal decomposition
• Surface-driven phase separation