Search

This paper describes the gelation of symmetric dendrimers based on building blocks constructed from L-lysine. These dendrimers form gel-phase materials in nonpolar organic solvents. The thermal properties and concentration dependence of the gelation were investigated, and it was found that there was a clear dendritic effect on the behavior of the soft materials formed, with higher generation dendrimers giving rise to more thermally stable gels. Variable temperature 1H NMR studies indicated that this behavior was probably a consequence of more extensive interdendrimer hydrogen bonding occurring between the peptidic groups in the higher generation dendrimers. The supramolecular aggregates were found to have a fibrillar structure, with the dimensions and alignment of the fibers being dependent on dendritic generation. Circular dichroism measurements confirmed that these fibers possessed chiral organization of the peptidic groups on the supramolecular (nano) scale, assigned as helicity. This paper indicates that dendritic functionalization provides a useful way of tuning gel-phase materials properties, with clear dendritic effects on gel formation being quantified for the first time, hence illustrating the way dendritic functionalization can play a positive role in the formation of highly functional organic materials with desirable properties.

A series of gold nanoparticles stabilised by ‘Newkome-type’ dendritic branching has been synthesised and fully characterised. In particular, the properties and behaviour of these hybrid materials are compared with those of a previously reported set of nanoparticles stabilised by dendrons constructed using l -lysine building blocks. The rates of cyanide-induced nanoparticle decomposition were determined, and it was found that the rate of decomposition increased on the introduction of dendritic branching. Furthermore, ‘Newkome-type’ dendrons were significantly more effective at protecting the encapsulated gold nanoparticle than the l -lysine based dendrons. It is proposed that this observation can be explained on the basis of more effective packing and surface coverage by the ‘Newkome-type’ dendrons. Importantly, this study therefore demonstrates that the organic chemical structure of dendritic ligands plays a crucial role in controlling the reactivity of self-assembled hybrid nanostructures.

Gold nanoparticles with diameters of ca. 13 nm were synthesised by UV irradiation of a supramolecular organogel into which HAuCl4 and tetraoctylammonium bromide had been diffused—the gel network plays an essential role in nanoparticle stabilisation.