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

Hyper-Rayleigh scattering has become the technique of choice for the detn. of the first hyperpolarizabilities of nonlinear optical (NLO) mols. Moreover, by exploiting the sensitivity of this second-order NLO-technique to mol. and supra-mol. symmetry, this technique was upgraded to a powerful spectroscopic tool. The authors 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-functionalized linear copolymers with different degrees of NLO-functionalization along the polymer backbone. The measurements show, in a unique way at the mol. level, that the dendrimers in soln. form globular structures at generations with 32 and 64 end-groups with restricted mobility of the end-group