Self-Assembly and Waterlike Anomalies in Janus Nanoparticles

We explore the pressure versus temperature phase diagram of dimeric Janus nanoparticles using Molecular Dynamics simulations in the NVT ensemble. The nanoparticles was modeled as a dumbbells particle, with two monomers connect by a rigid bond. The dimetic particle have one monomer that interacts by a standard Lennard Jones potential and a anomalous monomer that is modeled using a two-length scale shoulder potential. Monomeric and dimeric systems modeled by this shoulder potential show waterlike anomalies in bulk and in confinement. In this work, we investigate if a Janus nanoparticle composed by one anomalous monomer and a monomer without anomalous features will exhibit anomalous behavior and self-assembly structures. The influence of the non-anomalous monomer in the dimeric system properties was explored changing the interaction potential from a attractive Lennard-Jones to a purelly repulsive WCA potential. We show that the diffusion anomaly is maintained, while the density anomaly can disappear depending on the non-anomalous monomer characteristics . As well, the self-assembled structures are affected. A lamellar structure was observed, as well different kinds of micelles, as spherical and elongated micelles. Our results are discussed in the basis of the distinct monomer-monomer interactions and on the two-length scale fluid characteristics. The paper was accepted for publication at Langmuir (http://pubs.acs.org/doi/abs/10.1021/acs.langmuir.5b01555).