Anomalous phase behavior of liquid-vapor phase transition in binary mixtures of DNA-coated particles

作者：Martinez Veracoechea Francisco J^*; Bozorgui Behnaz; Frenkel Daan

来源：Soft Matter, 2010, 6(24): 6136-6145.

DOI：10.1039/c0sm00567c

We report a Monte Carlo study of a 1 : 1 binary mixture of particles coated with DNA chains with "sticky" ends. The system was modeled using a coarse-grained representation. In order to map out the phase diagram of this model system we combined biased Monte Carlo simulations with histogram reweighting techniques. We find that, at low temperatures (strong hybridization) this system undergoes a phase separation between a dilute vapor-like phase and a dense network-forming liquid-like phase. We observe a surprising non-monotonic dependence of the coexistence pressure on the temperature, or more precisely, on the reduced hybridization free energy (f(hyb)/k(B)T). This anomalous behavior can be understood in terms of a cross-over between two distinct regimes for the driving force of the phase transition: a hybridization-free-energy-driven regime and an entropy-driven regime. In the former regime, we observe a "normal" vapor-liquid equilibrium where during condensation, the system gains hybridization free energy but loses entropy. In the entropy-driven regime, the phase transition is driven by the increase in entropy due to the re-arrangement of sticky-end bonds in the liquid phase. Finally, we observe that the system can only undergo phase separation if the valence (i.e., the number of DNA-chains per particle) is larger than two. The coexistence region widens markedly as the valence is increased.

• 出版日期2010