Design, manufacturing and application of hybrid inorganic-organic nanomaterials.

Dendrimers are well defined, symmetrical polymers which have potential for a lot of different applications, ranging from catalysis to contrast agents and drug delivery. The high number of functional surface groups, which is increasing exponential with increasing dendrimer generation (size), makes them very suitable as building block for new nanomaterials and for systematic investigations. Here, positively charged polyamidoamine (PAMAM) dendrimers are encapsulated in the core of complex coacervate core micelles by complexing them with a negative – neutral block copolymer. The formed dendrimicelles have a hydrodynamic diameter of around 50 nm and a core size of 33 nm. Förster Resonance Energy Transfer (FRET) was utilized to prove the controlled incorporation of up to four different types of dendrimers into a single micellar core, thereby illustrating the versatility of the hierarchical building up of these micelles. In addition, FRET showed that the exchange dynamics of dendrimicelles can be controlled by using different dendrimer generations or by changing the pH. Furthermore, by exploiting dendrimicelles as a template to confine and organize the dendrimers, discrete dendrimer superstructures can be formed. After micelle formation, the dendrimers inside the micellar core are covalently cross-linked. Removal of the block copolymer from the assembly by increasing the salt concentration then leads to well-defined superstructures, coined dendroids, with a diameter of around 30 nm and a molecular weight of approximately 2.5 MDa. Depending on the crosslinker used, dendroid formation can be reversible. By incorporating dendrimer-encapsulated gold nanoparticles (AuDENs), the aggregation number of dendrimers inside dendroids is determined by counting the nanoparticles in TEM micrographs. TEM performed at different tilt angles and AFM analysis corroborate formation of stable, three-dimensional structures.