For the simulations, BrC was assumed to be capable of transporting between the two phases as describe in Shiraiwa, PCCP 2013. The justification for this assumption is discussed in the supplementary material (section S4). The initial molar concentration of the two different condensed phases was assumed to be equal, and the activity coefficients of BrC in both condensed phases was assumed to be 1, resulting in equal concentrations of BrC in both condensed phases at equilibrium. However, we also varied this assumption, and found the lifetime of BrC were not sensitive to the relative concentrations of BrC in the two phases (sections S3.1).