The effect of terminal group modification on the solution properties of dendrimers: A molecular dynamics simulation study

摘要

We study the static and dynamic properties of amphiphilic dendrimers of generation 3 through 7 in an explicitly modeled solvent with molecular dynamics. All interior monomers are solvophobic while the terminal monomers are varied from all solvophobic to all solvophilic, with a number of nonuniform solvophobic/ solvophilic terminal monomer arrangements investigated. For generations 6 and 7, crowding at the dendrimer surface forces some solvophilic monomers into the interior of the molecule. The nonuniformly surface-modified dendrimers are studied to examine how different arrangements of terminal monomers might affect dendrimer conformation. In all cases with solvophilic terminal monomers we find the solvophilic monomers congregating at the surface; thus, the dendrimer adopts the form of a unimolecular micelle. For generation 5 and smaller, the terminal monomer arrangement has no effect on the static or dynamic properties. For generations 6 and 7, a minimum number of bonds between the two types of terminal monomers is required to observe all solvophilic terminal monomers at the surface of the molecule. Lowering the simulation temperature, which effectively increases the interaction strength between solvophilic monomers and solvent, eliminates the backfolding tendencies of the solvophilic monomers and increases the asphericity of the generation 6 and 7 dendrimers.