| Photorefractive hyper-structured molecules(HSM) are molecules that combine different functional photorefractive components such as charge transporting group(CT) and nonlinear optical chromophore(NLO) together to form a complex molecule, and realize its photorefractive effect through the synergy among the components. In this paper, five small functional molecules were synthesized, then they were introduced into the MCRA core to prepare seven photorefractive HSM. This method can avoid the problems that the NLO chromophores is difficult to introduce and determine its contents.Firtly, the hydroxyl-containing functional molecules Cz-OH and Cz CSN were synthesized, then four HSM CRA-CSNx-Cz(100-x)(where x = 100, 75, 50, 25 represents the molar ratio of Cz CSN and carboxyl groups of MCRA) containing both NLO chromophore and CT were prepared via esterification reaction between carboxyl-containing MCRA core and hydroxyl group-containing functional molecules, respectively. Their chemical strutures were characterized by 1H(13C) NMR, FT-IR, EA, etc. GPC results show that the synthesized HSM have narrow PDI distribution. The element analysis results of CRA-CSN100-Cz0 show that the average introuduced number of CSN chromophores into MCRA core are about 4.6, and the esterification rate is about 57.5%. With the increase of CSN chromophores content, their thermal stability are increased.In the second part, in order to further investigate the effects of different choromophores on the PR properties of HSM, the other three hydroxyl-containing NLO functional molecules Cz MN, Cz SN and Cz CMA were synthesized. Then, three CRA-Meth.(where Meth.= MN, SN, CMA represent choromophores with different structure) were synthesized using the same method as CRA-CSN100-Cz0. Their chemical structures were confirmed by 1H(13C) NMR, FT-IR, EA, etc. The average number of introduced chromophores calculated from EA results are about 4-5, and the esterification rates are 50% to 62.5%. CRA-Meth.(Meth.=CSN, MN, SN, CMA) have a good solubility in common solvents such as THF, CHCl3. Their maximum absorption wavelength of UV-Vis absorption spectra are related to the structures of the chromophores. The decomposition temperatures measured by TG of the synthesized HSM are all higher than 225℃.Finally, the photorefractive properties of HSM were evaluated by two-beam coulping(TBC) experiments. All of the HSM showed significant TBC signals. Compared with methylene small molecules, all the photorefractive properties of corresponding HSM have been improved. Their TBC gain values are largely influenced by the concentration of chromophoresin molecules, the length of conjugated chromophores and the asymmetry of methylene molecular structure. Among the seven HSM doped photorefractive system, CRA-CSN100-Cz0 doped system has the best photorefractive performance, which TBC gain value is 78.2cm-1. |
