Simulation of a Symmetric Binary Mixture of Charged Dendrimers Under Varying Electrostatic Interactions: Static and Dynamic Aspects

A symmetric binary mixture of terminally charged trifunctional-core/difunctional-branched dendrimers of the third and the fourth generation is examined in explicit solvent solution by means of molecular dynamics simulations. The static and dynamic response of the components is monitored under a varying strength of electrostatic interactions. The response of the dendrimer constituents shares common features as the intensity of Coulombic interactions increases, but characteristic differences are noted in the individual structural arrangement and their dynamic response. An effective-charge modulation develops across the dendritic structure and at the immediate vicinity of each molecule. The asymmetry in size and in the overall charge between the two components affects the packing properties of the molecules resulting in different morphologies compared to the respective single component systems. In addition, individual translational and rotational motion of the dendrimers exhibits distinct behavior in different Coulombic regimes. The motional contrast between the two components differentiates their relative dynamic response as the electrostatic interactions grow stronger. The increase of Coulombic interactions drives the components of the mixture to a dynamically arrested state, but the eventual vitrification takes place at different levels of electrostatic interactions depending on dendrimer generation. The findings of the present study elucidate several aspects of the behavior of these charged soft-colloidal materials and offer new insight toward the control of their long-range order and of their dynamic properties.