How stable are amphiphilic dendrimers at the liquid–liquid interface?

By means of molecular dynamics simulations the free energy of adsorption of model dendrimer characterized by monomers of different chemical affinity is predicted as a function of the number and position of the monomers. The results show that modifying the affinity of the only end-monomers with one of the two solvent components (amphiphilic dendrimer) is enough to remarkably increase the stability of the molecule at the interface. The results also indicate that the so called Janus-dendrimer, where only half of the end-monomers are modified, does not show a higher interfacial stability compared with standard amphiphilic one. These findings compare well with simulation results obtained from atomistic simulations performed on polyaminoamide dendrimer at the air–water interface. The free energy profiles have also been compared with those obtained from simpler models which treat the dendrimer molecule as a rigid sphere showing that such simplification is acceptable in poor solvent but not in good solvent where the flexibility of the dendrimer molecule plays a major role in its stability at the interface. These calculations will help in the design of new amphiphilic dendrimers and in predicting their properties at liquid–liquid interface.