Properties of Dendrimers with Flexible Spacer-Chains: A Monte Carlo Study

Abstract

We study the properties of starburst dendrimers with flexible spacers in good solvent using Monte Carlo simulations based on the bond fluctuation model by systematic variation of dendrimers’ generation number G and spacer length S. Our simulations support the dense-core picture of dendrimers due to a substantial decrease of monomer densities with the radial distance from the dendrimers’ center of mass. The interior of dendrimers is penetrated by the terminal groups due to finite values of the end-group densities in that area indicating backfolding of the terminal groups toward the molecules’ interior. The mean instantaneous shape of dendrimers changes monotonously from oblate to spherical as the increase in their molecular weight N is caused by an increase in G, while for fixed G it is hardly affected by variations of S. Using a mean-field model for the dendrimer extension reveals spacers as nearly unperturbed linear chains in good solvent and the dendrimer’s conformation is a result of rearrangement of spacer chains up to a limiting generation of about G = 9. In particular, the radius of gyration follows the predicted scaling behavior of Rg/Sν ∼ (N/S)1/5G2/5. Upon appropriate rescaling of length scales, extension measures, monomer distributions, and shape factors display spacer-length scaling. As a result dendrimers in good solvent display universal properties with respect to the length of spacers up to a rather high number of generations.