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

Hyper-Rayleigh scattering has become the technique of choice for the determination of the first hyperpolarizabilities of non-linear optical (NLO) molecules. Moreover, by exploiting the sensitivity of this second-order NLO-technique to molecular and supra-molecular symmetry, this technique was upgraded to a powerful spectroscopic tool. We did this by probing the symmetry of NLO-functionalized dendrimers, measuring the first hyperpolarizability at different generations. These results are compared with measurements on side-chain NLO-funtionalized linear co-polymers with different degrees of NLO-functionalization along the polymer backbone. 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 end-groups with restricted mobility of the end-groups.