Universal scaling of the diffusivity of dendrimers in a semidilute solution of linear polymers

TL;DR

This study uses simulations to reveal universal scaling laws for dendrimer diffusivity in semidilute solutions, showing they are more spherical and dense than linear chains, with unique diffusion behaviors that differ from nanoparticles.

Contribution

It introduces a new scaling law for dendrimer diffusivity accounting for their size reduction with increasing concentration, and compares their behavior to nanoparticles and linear chains.

Findings

Dendrimers and linear chains follow universal scaling laws for size and diffusivity.

Dendrimers are more spherical and have dense cores compared to linear chains.

Dendrimers exhibit subdiffusive behavior with higher exponents than nanoparticles.

Abstract

The static and dynamic properties of dendrimers in semidilute solutions of linear chains of comparable size are investigated using Brownian dynamics simulations. The radius of gyration and diffusivity of a wide variety of low generation dendrimers and linear chains in solution follow universal scaling laws independent of their topology. Analysis of the shape functions and internal density of dendrimers shows that they are more spherical than linear chains and have a dense core. At intermediate times, dendrimers become subdiffusive, with an exponent higher than that previously reported for nanoparticles in semidilute polymer solutions. The long-time diffusivity of dendrimers does not follow theoretical predictions for nanoparticles. We propose a new scaling law for the long-time diffusion coefficients of dendrimers which accounts for the fact that, unlike nanoparticles, dendrimers shrink with an increase in background solution concentration. Analysis of the properties of a special case of a higher functionality dendrimer shows a transition from polymer-like to nanoparticle-like behaviour.