The symmetry of functionalized poly(propylene imine) dendrimers probed with hyper-Rayleigh scattering

Dendrimers are well-defined highly branched macromolecules that emanate from a central core and are synthesized through a stepwise, repetitive reaction sequence. In this study, different generations of a poly(propylene imine) dendrimer have been functionalized with second-order non-linear optical chromophores. The non-linear optical properties of these macromolecules have been investigated using the hyper-Rayleigh scattering technique. The sensitivity of this technique to molecular symmetry is exploited. The measurements show, in a unique way at the molecular level, that the dendrimers in solution form globular structures at generations with 32 and 64 4-dimethylaminophenylcarboxamide end-groups with restricted mobility of the end-groups.