Preparation And Polarization Of Nonlinear Optical Materials Containing Six-branched Chromophores

Nonlinear optical (NLO) materials have been recognized for several decades as a promising field in the domain of optical switching, optical information processing, and electro-optic modulation. Compared with inorganic materials, organic polymers are currently attracting considerable research interest for their large nonlinear optical coefficients, low dielectric constants, and excellent of processing. To date, a lot of typical D-π-A chromophores that are endcapped with electron donor units and electron acceptor units have been explored at highβvalues up to now. However, the conversion from quite highβvalues of chromophores to large macroscopic optical nonlinearities is difficult to realize, mainly due to the very strong inter-chromophore dipole-dipole interactions. In order to solve this problem, dendritic structures have been used in NLO materials, and dendronized organic nonlinear optical materials have been the subject of research.In this paper, the theories of NLO effect and second-order nonlinear optical materials are briefly introduced, the poled polymer are also reviewed. Different types and recent progress of dendronized organic NLO materials are described in detail. A series of multi-branched chromophores were synthesized which were guided by the theories of reactions. The films containing multi-chromophore dendrimers were fabricated through a handy way and poled via efficient methods. The second-order nonlinearities of films were also investigated.Bichromophore DN and six-branched chromophore SN were produced through esterification reactions. Chromophore N1 and bichromophore DN were fabricated to be polymer films and the neat film containing six-branched chromophore SN with excellent optical property was prepared successfully. The second-order nonlinear optical activity of poled films showed the second harmonic generation (SHG) coefficients (d33) of Film-SN. Film-DN and Film-N1 were 208 pm/V.39 pm/V and 25 pm/V. solving the decline of nonlinear optical property from the strong electrostatic interactions between chromophores and providing the experience for the preparation of NLO materials containing multi-chromophore molecules.On basis of isolation theory, six-branched chromophores S1, S2, S3 with different isolation substituents were gained via esterification reactions and the films were manufactured from 1-3 types of chromophores directly. The neat thin films containing six-branched chromophores displayed enhanced nonlinear optical coefficient (d33 values were 113 pm/V,142 pm/V and 136 pm/V). compared with the polymer films doped corresponding azo chromophores, with about 2-3 times improvement. And the mixed films showed the largest d33 values among all films. The results showed six-branched construction could boost the nonlinear optical activity dramatically, and further improvement could be obtained when isolation groups were introduced, especially the rigid spacers. The mixed films enhanced more than other films in second-order nonlinear optical property.