Effective interactions between charged dendrimers

We perform monomer-resolved computer simulations of fourth-generation charged dendrimers at various conditions of charging (full, terminal and neutral) and for different values of the spacer length P connecting the branching nodes, from P = 1 to P = 6. We examine the sizes, overlaps and effective forces between the centers of mass of the dendrimers with and without added monovalent and divalent salt. For neutral dendrimers, we find that all effective interactions for the various spacer lengths can be scaled on a universal curve. Adding charge to the dendrimers leads to increased repulsions between them, which can be tuned by the spacer length P and become softer as the latter increases. Addition of monovalent salt of various concentrations leads to no visible effects on the effective interaction, in contrast to divalent salts, which cause a dramatic reduction of the effective repulsion as the salinity increases.