Molecular assembled structure and nonlinar optical property of azobenzene dendrimers

Nonlinear optical dendrimers were synthesized, and their conformation properties and molecular nonlinear optical properties were clarified by second-order nonlinear optical measurements. The synthesized dendrimers were modified by azobenzene chromophore. The molecular hyperpolarizability was measured by the hyper-Rayleigh scattering method. The molecular hyperpolarizabilities of dendrimer were much higher than that of the azobenzene monomer. The polarized nonlinear optical measurement provided structural information on the dendrimers and indicated that each chromophore unit was oriented noncentrosymmetrically along the molecular axis to become a cone shape. Energetic results by molecular dynamics calculations supported the experimental results, where dendrimers tend to a molecularly assembled structure rather than a spreading and spherical one.