Design, Synthesis And Properties Of Novel Second-Order Nonlinear Optical Organic Chromophores

Organic second-order nonlinear optical (NLO) materials have attracted much attention in the past two decades due to their huge potential applications in many different fields and many advantages over inorganic materials such as large nonlinearities, ultrafast response, high optical damage threshold, low dielectric, good processbility, integrability etc. One of the major challenges in this research is to design and synthesize second-order NLO chromophores possessing simultaneously large first-order molecular hyperpolarizability (β), good transparency and thermal stability; another is multifunctionalized polymeric NLO materials heralded as promising for application in high-tech.Chapter 1 gives a brief introduction on nonlinear optics, and recent progress of organic second-order nonlinear optical chromophores are reviewed from three aspects: the synthesis of new chromophores with large β value, the synthesis of new chromophores with large β value and good thermal stability, the synthesis of new chromophores with large β value and good transparency. Then the research strategy of the thesis is presented.In chapter 2, eight novel chromophores, in which N-hexylindole acts as an electron donor and furan or thiophene ring as a part of the conjugation bridge, are synthesized and characterized by ~1H-NMR, IR, UV-Vis spectra and elemental analysis.In charpter 3, eight new two-dimensional NLO chromophores containing triphenylamine with A type structure are designed and synthesized, and the corresponding one-dimensional NLO chromophores (common D—π— A type) are also synthesized for comparison. Their structure has been verified through the characterization of ~1H-NMR, IR, UV-Vis spectra and elemental analysis.Chapter 4 briefly describes the principle of Hyper-Rayleigh Scattering (HRS) method, which is used to determine the μβ values of NLO chromophores. Then the linear optical and thermal properties of the chromophores, which are synthesized and characterized in Chapter 2 and Chapter 3, are discussed. UV-VIS absorption phenomena of the four indole-based furan chromophores show 26~30nm blue-shifted absorption when compared with 5-[2-(4-diethylaminephenyl)vinyl]furan analogues. And this fact confirms our initial designing thought that indole-based chromophores can exhibit better transparency when compared with similar dialkylaniline-based chromophores. TGA results show that indole-based chromophores and triphenylamine-based chromophores are thermally stable up to 337℃ and 340℃, respectively. The measurement of these chromophores' nonlinear optical properties is now in progress.