Functionalised polyphenylene dendrimers and their applications

In this chapter is described the development of polyphenylene-based shape-persistent dendrimers as functional materials. Functional groups can be incorporated into such dendrimers in the core, in the scaffolding, or on the periphery. The rigidity and shape-persistence of the structure means that the functional groups are in well-defined spatial relationships to each other, which is advantageous for both the control of and the study of energy and charge transfer processes between them. Electrophoric and chromophoric units, including conjugated polymers, have been used as functional cores and the dendronisation has been found to have effects upon their opto-electronic properties. Efficient energy transfer occurs between dyes attached at the surface, in the scaffold and at the core, offering possible applications in light-harvesting systems. Dendrimers bearing biologically active moieties such as peptides or biotin have been made for bioassay applications, and as agents for RNA transfection. Attachment of suitable substituents, e.g. poly(ethylene oxide) chains, on the surface enables core-shell systems to be made with possible applications as supports for catalysts. Desymmetrisation opens the way to bifunctional nanoparticles, for example a dendrimer bearing both a biotin for binding to streptavidin and dye chromophores for visualisation.