MOLECULAR-DYNAMICS STUDY OF DENDRIMER MOLECULES IN SOLVENTS OF VARYING QUALITY

The properties of dendrimers (''starburst'' molecules) under varying s olvent conditions are studied using molecular dynamics simulations. Th e dendrimers are found to have a compact (space filling) structure und er all solvent conditions, with a radius of gyration which scales with the number of monomers as R(G) proportional to N-1/3. For high genera tion number dendrimers, there is a distinct region of constant monomer density. The density in this region depends only on the solvent quali ty and is independent of the generation number. When the contributions of the different generations to the overall density profile are separ ated, we find that the monomers which belong to the first few generati ons are stretched and spatially localized. Later generations are less localized and penetrate well into the central regions of the dendrimer . The different primary branches (''dendrons'') of the dendrimers are found to be segregated. The amount of spatial overlap between the diff erent dendrons decreases with increasing generation number of the dend rimer and increasing solvent quality. The relaxation times of the fluc tuations of the internal structure were evaluated as well, to ensure t hat the simulations were run long enough for adequate sampling.