Christian Rossner

Planet–Satellite Nanostructures Made To Order by RAFT Star Polymers

The investigation and application of complex nanostructures requires the hierarchical arrangement of distinct domains on a small scale. Herein, we report a method to prepare planet-satellite arrangements using RAFT polymers. Our approach is based on star polymers decorated with trithiocarbonate groups on their outer periphery that attach to gold surfaces and thus provide the polymer with the ability to connect (larger) gold nanoparticle planets with (smaller) gold nanoparticle satellites. By adjusting the molecular weight of the polymeric linker, nanostructures with tailored planet-satellite distances, as evidenced by transmission electron microscopy, are obtained. This strategy offers a straightforward way to prepare gold nanoparticle scaffolds with multiple reactive functionalities at defined distances from the central core.

The Structure of Gold-Nanoparticle Networks Cross-Linked by Di- and Multifunctional RAFT Oligomers

Gold nanoparticle (AuNP) network structures featuring particles from the two-phase Brust-Schiffrin synthesis and linear RAFT oligomers of styrene with two and multiple trithiocarbonate (TTC) groups along their backbone have been investigated in detail. Insights into the internal structures of these particle networks could be obtained from small-angle X-ray scattering experiments, showing that primary AuNPs are cross-linked by the employed molecular linker. The extent of AuNP network formation was investigated by means of dynamic light scattering and UV/visible extinction spectroscopy, showing an abrupt attenuation of network formation after a critical degree of polymerization of the cross-linker is exceeded. Analysis of transmission electron micrographs indicated a three-dimensional shape of the particle superstructures, which is evenly filled with the primary AuNPs. From the results obtained in this study, guidelines for the fabrication of nanoparticle networks from the self-assembly with macromolecular cross-linkers are suggested.

Nanocomposites and Self-Assembled Structures via Controlled Radical Polymerization

We report recent findings on the formation of nanocomposites and self-assembled hybrid nanoarchitectures, in which controlled radical polymerization plays a key role. Specifically, we address how macromolecular design via these controlled methods can be used to flexibly guide the formation of hybrid nanoarchitectures in a rational and predetermined fashion. To this end, the role of polymeric architecture in tuning polymer/inorganic nanocomposite structures is examined.

Uniform Distance Scaling Behavior of Planet–Satellite Nanostructures Made by Star Polymers

Planet-satellite nanostructures from RAFT star polymers and larger (planet) as well as smaller (satellite) gold nanoparticles are analyzed in experiments and computer simulations regarding the influence of arm number of star polymers. A uniform scaling behavior of planet-satellite distances as a function of arm length was found both in the dried state (via transmission electron microscopy) after casting the nanostructures on surfaces and in the colloidally dispersed state (via simulations and small-angle X-ray scattering) when 2-, 3-, and 6-arm star polymers were employed. This indicates that the planet-satellite distances are mainly determined by the arm length of star polymers. The observed discrepancy between TEM and simulated distances can be attributed to the difference of polymer configurations in dried and dispersed state. Our results also show that these distances are controlled by the density of star polymers end groups, and the number of grabbed satellite particles is determined by the magnitude of the corresponding density. These findings demonstrate the feasibility to precisely control the planet-satellite structures at the nanoscale.