Study On The Synthesis And Preparation Method Of The Novel Second-order Nonlinear Optical Films

The second-order nonlinear optical (NLO) materials are gaining more attention due totheir extensive application prospect in information processing, broad bandwidthtelecommunication, and high-density optical storage. Comparing with inorganic materials,organic NLO materials with attractive features, such as larger electro-optical coefficient,faster response, lower dielectric constant, higher laser damage thresholds, low cost andeasy to process, are extremely important for addressing the present encountered limitationsin optical interconnect technologies. However, a huge challenge for the scientists now is toobtain macroscopical non-centrosymmetric and thermal stable materials. The commonways to make chromophoric arranged with orientation in the organic polymer are listed asfollows： electric-field poling technique, Langmuir-Blodgett (LB) film technique,Layer-by-Layer (LBL) assembly technique. The NLO polymer can be classified to poledpolymer materials，NLO LB materials and NLO assembly film materials considering thedifferent ways to make chromophores distribute in the organic polymer.In chapter1, a brief introduction about the basic principle and new development ofNLO materials, as well as description and summary about the development of three generaltypes of NLO materials mentioned above, from which drawn out the studying ideas of the whole paper, have been presented.In chapter2, we proposed the semi-main-chain structure of the phenolic resinNLO materials, in which the chromophores are partly connected to the polymermain chain, and partly perpendicular to the polymer main chain. It can effectivelyprevent the relaxation of the chromophore after poling. Owing to the introduction ofepoxy group, the phenolic resin can be slowly solidified at a lower temperature inthe presence of amine when the NLO films are in a high DC electric field. Thismethod is able to preserve the poling-induced polar order of organic materialsagainst thermal relaxation. All the intermediate and final products werecharacterized by IR and UV spectrurm. TGA determination showed that thesecond-order nonlinear optical materials have a high thermal stability. Theelectro-optic coefficient (r33) optical film measured with simple reflection methodcan reach up to10.42pm/V It remains at95%of the initial value even after beenplaced at80℃for100hours.In chapter3, we discuss a thermosetting phenolic resin and the chromophoremolecules with simple structure. The guest-host systems can solve these problemsmentioned above while obtaining high thermal stability of second-order nonlinearoptical materials. The second–order nonlinearity of the polymers was measured withsimple reflection technique at1.3μm wavelengths. The values of electro-opticcoefficient (r33) of the different chromophore concentration systems were4.82,6.50,11.10,12.62,16.32pm/V respectively and they were both stabilized around95%oftheir initial values after100h at80℃. All the chemical structure of theintermediates and final products were characterized by IR and UV-vis spectrurm.TGA determination showed that the second-order nonlinear optical materials were ofhigh thermal stability.In chapter4，we designed NLO LBL film based on the charger-transfer interaction, in which carbazole group is the electron donor while dinitrobenzenegroup is the electron acceptor. More importantly, the electron donor and electronacceptor are connected to the same polymer to complete the process ofself-assembly by themselves with time going. All the chemical structure of theintermediates and final products were characterized by IR and UV-vis spectrum.According to the UV-track, both the assembly processes of the two films can besmooth, continuous and controllable. In chapter4we also design a NLO LBL filmbased on the electrostatic attraction interaction, the novelty of the design is that thediazonium salt and the carboxyl group are connected to the same polymer tocomplete the process of self-assembly by themselves with times. All theintermediate and final products are characterized by IR and UV-vis spectrum.According to the UV-track, both the assembly processes of the two films can besmoothly and with good continuity and controllability.