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Synthesis Two-dimensional Spindle-type Chromophores And Preparation Materials

Posted on:2012-11-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:X L ZhangFull Text:PDF
GTID:1101330335452945Subject:Polymer Chemistry and Physics
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Second-order nonlinear optical (NLO) materials have attracted considerable attention due to their potential applications in broad bandwidth telecommunication, information processing, and high-density optical storage, etc. Electro-optic (EO) materials, which possess large and rapid NLO responses, low dielectric constant, high laser damage thresholds, low cost, superior chemical flexibility and ease of process, have been predicted to be the NLO polymers closest to commercialization. Especially organic second-order nonlinear chromophore acquired an enormous progress. A lot of molecules with large hyperpolarizabilities and excellent thermal and chemical stability were designed and synthesized. Before their commercialization, it is a challenge to synthesize EO polymers with large NLO effects, high thermal stability of the dipole moment after poling and low optical loss to fit the requirements of EO apparatus.In this dissertation, we have provided some promising attempts to synthesize novel organic chromophores. We present the synthesis of a series of two-dimensional spindle-type chromophores. The chromophores were used to prepare host-guest doped second-order nonlinear optical films. We designed and synthesized a series of PU based on spindle-type chromophores, and the PU/Poly(MMA-co-GMA) doped cross-linked films were prepared. We have successfully synthesized novel photo-cross-linked NLO materials (PU/PMMA) containing spindle-type chromophores. Second-order nonlinear optical organic/inorganic hybrid film containing two-dimensional spindle-type chromophores was successfully prepared via sol-gel process.In chapter 2, we present the synthesis, characterization of two-dimensional spindle-type chromophores STC-1 to STC-4. The two-dimensional spindle-type chromophores were accomplished by three different strategies:Suzuki cross-coupling reaction, Wittig reaction, Knoevenagel condensation reaction. All of the compounds were characterized by 1H-NMR spectrum and IR spectrum. Thermogravimetric analysis showed that two-dimensional spindle-type chromophores exhibited good thermal stability. All of the absorption wavelengths (λmax) of chromophores were less than 480 nm, which proved that the chromophores possessed good transparency in the visible region. The host-guest doped second-order nonlinear optical films were prepared by the chromophores and Poly(GMA-co-MMA). The cross-linked network structure formed in films after poling process. The EO coefficients of the guest-host doped films were measured with the Teng-Man setup. The temporal stability of EO response was found to be good, as the r33 value of the films maintained more than 85% of their original value after holding at 80℃in air over 200 h.In chapter 2, we also present the synthesis of two-dimensional fluorinated spindle-type chromophores STC-1F and STC-2F. Dimethylamine was used as electron donor and 3,4,5-trifluorophenyl was used as side groups for chromophores STC-1 and STC-2 investigated. Chromophore STC-1 with TDC as electeron acceptor and chromphore STC-2 with 4-nitrobenzylcyanid as electeron acceptor were investigated. Two-dimensional fluorinated chromophores were characterized by 1H-NMR,19F-NMR and IR spectrum. Thermogravimetric analysis showed that the chromophores displayed high thermal stability. The maximum absorption wavelength (λmax= 482 nm) of fluorinated chromophore STC-1 was blue shift 8 nm in comparison with the nonfluorinated chromophore (λmax= 490 nm) in chloroform, which increased the optical transparency in the visible region. The guest-host doped films were prepared by the chromophores and PMMA. To further explore the alignment of the chromophore moieties in the chromophores/PMMA poled films, the order parameter (Φ) was measured. STC-1 F/PMMA doped films exhibited very highΦvalues, up to 0.26 higher than 0.17 for STC-2F/PMMA doped film. The testedΦvalues were well in accordance with their r33 values.In chapter 3, we designed and synthesized a series of PU based on spindle-type chromophores. All of the copolymers were characterized by 1H-NMR and IR spectrum. The molecular weight and molecular weight distribution were determined by gel permeation chromatography-refractive index-multi-angle laser light scattering detection techniques. DSC thermograms showed that polyurethanes generally have different Tg with different content of chromophores. PU-4 and PU-DR19 have the same content of chromophores, but the Tg of PU-4 is higher than PU-DR19. The relatively higher Tg of PU-4 might be caused by its rigid main-chain structure. In order to enhance the thermal and temporal stabilities of the NLO materials, the PU/Poly(MMA-co-GMA) doped cross-linked films were prepared. The surface morphology of the films was characterized by the AFM images. The surface of the films was extremely flat before poling. But the surface of the films resulted in numerous hills and valleys after poling, which caused by the chromophore moieties alignment in the poling direction. The EO coefficient of PU-2/Poly(MMA-co-GMA) cross-linked film was obtained up to 32 pm/V. Compared with their analogue copolymer containing DR-19, they displayed much better EO coefficient and thermal stability due to their large hyperpolarizability and unique structure. In chapter 4, we synthesized PU with double-ended photo-cross-linkable groups containing spindle-type chromophores. A preliminary study of the NLO properties of the cross-linked film is presented. The PU was prepared by 2-hydroxyethyl methacrylate (2-HEMA) and NCO-terminated chromophore, which was obtained from an addition reaction of spindle-type chromophore with an excess amount of 4,4'-Methylenebis (cyclohexyl isocyanate). The chemistry reaction course was characterized by IR spectrum. TGA thermograms showed that the temperature of the 5% weight loss was 212℃and 228℃for before and after photo-cross-linking, respectively. This result indicated that the cross-linked network structure can be benefited its stability against heating. The second-order optical property of the prepared film was measured by Teng-Man technique and achieved a high EO coefficient up to 41 pm/V. The thermal and temporal stability of the film was improved by photo-cross-linking. The functionalized alkoxysilane dye (ICTES-STC) was formed by the reaction of two-dimensional spindle-type chromophores (STC) with 3-isocyanatopropyltriethoxysilane (ICTES). Second-order nonlinear optical organic/inorganic hybrid film containing two-dimensional spindle-type chromophores was successfully prepared via sol-gel process. The thermogravimetric analysis showed that the initial decomposition temperature of the hybrid film is 269℃. This result indicates that the covalent linkage between the chromophore and silica matrix could prevent the decomposition of the chromophore. After corona poling, the EO coefficient of the hybrid film was calculated to be around 12 pm/V. The results showed that the hybrid film exhibited excellent thermal stability and NLO property.
Keywords/Search Tags:Nonlinear optics, Spindle-type chromophore, EO coefficient, Cross-linked optical film
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