The Janus Character of Heterogeneous Dendritic Nanoparticles.

graphical abstract
Chute, J.A.; Hawker, C.J.; Rasmussen, K.O.; Welch, P.M.;
44, 1046- 1052.

We present a computational and theoretical study of dendrimer-based nanoparticles composed of two linear chain types attached to the terminal groups of a core dendrimer. The chains were coupled to the dendritic core in both topologically Janus and alternating configurations. We find that a straightforward extension of the well-known scaling theory for the size of star polymers due to Daoud and Cotton works well for these classes of molecules. This suggests that the chains preferentially stretch radially from the molecular center. As a result, we find that topological connectivity alone suffices to ensure the stability of a Janus configuration. Chemical mismatch that drives phase separation in melts of these chains does not dramatically affect Janus structures when they are topologically constrained and can only produce frustrated conformations in alternating assemblies in the molecular weight range studied herein. We also demonstrate that contrast variation scattering experiments are ideally suited to detecting the presence of Janus structures. Specifically, we propose a scalar metric based upon contrast variation scattering studies on a single class of nanoparticles that can capture the extent of their Janus nature.