Energy transfer in supramolecular assemblies of oligo(p-phenylene vinylene)s terminated poly(propylene imine) dendrimers

Poly(propylene imine) dendrimers have been functionalized with pi-conjugate d oligo(p-phenylene vinylene)s (OPV's) through an amide linkage and are ful ly characterized. In solution the dendrimers behave as globular entities wi thout specific interactions between the OPV units. The OPV dendrimers have an amphiphilic nature and self-assemble at the air-water interface forming stable monolayers in which the dendritic surfactants presumably adopt a cyl indrical shape; all the OPV's are aligned perpendicular to the water surfac e, and the dendritic poly(propylene imine) cores face the aqueous phase. Op tical spectra taken from Langmuir-Blodgett films show a small blue shift in dicative of interactions between the OPV units. Spin-coated homogeneous thi n films could be obtained from solutions containing dendrimers loaded with dyes. The optical properties of these films are similar to the Langmuir-Blo dgett films which points to the same type of organization of the OPV's. The OPV dendrimers are effective extractants of anionic dye molecules from wat er to organic solvents. Ratios between dye and dendrimer can be easily tune d by varying the concentration of dye in the water layer. The host-guest as semblies show not complete energy transfer from the OPV units to the encaps ulated dye molecules in solution. The energy transfer is very efficient in spin-coated films of dendrimer/dye assemblies and the emission wavelength c an be adjusted by using a variety of dye molecules. The dendrimer/dye syste ms mix very well with poly(p-phenylene vinylene)s (PPV's) forming good qual ity thin films in contrast to films obtained from dye/PPV without dendrimer . The OPV units in the dendrimer act as a compatibilizer in these systems a nd energy transfer is observed from the organic PPV polymer to the dye. It gives the possibility of tuning the emission wavelength of the PPV thin fil ms by using the appropriate encapsulated dye.