Synthesis And Nonlinear Optical Properties Of Hybrid Films Containing Heterocyclic Chromophores

Over the past two decades,nonlinear optical(NLO)materials have been of great interest due to their potential applications in the fields of optical information processing,optical sensing,and telecommunications.Inorganic-organic hybrid material through sol-gel strategy offers the great opportunity for the development of the NLO materials.In the latter,the NLO chromophores are incorporated into the inorganic matrix by one or more covalent bonds.These hybrid materials capitalize on the unique properties offered by the two components to generate novel materials with desired characteristics,therefore,they are considered as promising candidate for NLO device applications and have been the subject of NLO materials research.In this thesis,the basic theories of NLO and molecular design theory are briefly introduced,the research progress of second order NLO materials are also reviewed. Base on this,three kinds of heterocyclic chromophores are synthesized and further react with 3-isocyanatopropyl-triethoxysilane(ICTES)to give alkoxysilane dyes (ASD)via a urethane reaction.Theβ_CTμ_g values of the chromophores EBTC,EBOC and FS are evaluated by solvatochromic method which display 7438×10^-30, 5689×10^-30and 3599×10^-30esu·D respectively,more higher than DR1.Molecular structures of the resultants are confirmed by elemental analysis,FTIR and ¹H-NMR. The transparencies and thermal stabilities of the compounds are detected by UV-Vis, TGA,and DSC.The thermal decomposition temperatures of these three chromophores are all over 220℃.Followed by a sol-gel process of the alkoxysilane dyes,the inorganic-organic hybrid nonlinear optical(NLO)films are successfully prepared.The second harmonic coefficients(d₃₃)of the hybrid films are measured by in situ second harmonic generation(SHG)measurement,respectively.The hybrid films exhibit large optical nonlinearity.The d₃₃values of hybrid films containing EBTC and EBOC are 23.7 pm/V and 9.27 pm/V respectively.And the hybrid films exhibit good thermal stability.The half-decay temperatures are at 150℃.The results reveal that the hybrid film containing benzothiazole exhibited better properties than it's analogue containing benzoxazole.A series of hybrid films with different matrix are also prepared by using the precursors ASD-FS,tetraalkoxysilane(TEOS)and 3-(trimethoxysilyl)propyl methacrylate(TSPM)in various molar ratios.Transparent films are only fabricated with the sol containing high concentration of TSPM.Higher concentration of TSPM is found useful to abate dipolar chromophore interactions and consequent aggregation problems.Second-order NLO properties and temporal stability of sol-gel films are also investigated by virtue of in situ second harmonic generation (SHG).