Study On The Preparation And Properties Of Novel Second-Order Nonlinear Optical Chromophores And Hybrid Materials

Recently, various novel and high performance second-order nonlinear optical (NLO) organic polymer materials, owing to their wide application in electro-optical (E-O) modulated devices and advantages superior to inorganic materials, have been prepared and investigated by numerous scientists. It is still considered to be a challenge for researchers to prepare novel polymer lattices with macroscopically non-centrosymmetric structure and in which chromophoric dipolar molecules arranged with orientation. A lot of molecules with large hyperpolarizabilities and excellent thermal and chemical stabilities were designed and synthesized. And organic-inorganic hybrid materials, which were fabricated by incorporating the NLO chromophores into the inorganic matrix by covalent bonds, capitalize on the unique properties offered by the two components to generate noval materials with desired characteristics. Therefore, they are considered as promising candidate for NLO device applications and have been the subject of Non-linear Optical materials. The theory and development of these types of NLO organic molecules and hybrid film materials have been reviewed in chapter 1. In this dissertation, we have provided some promising attempts to fabricate novel high performance and thermal stability thiophene-containing and"spinle-like"NLO organic chromophores and hybrid films, respectively.In chapter 2, we have synthesized and characterized a series of new chromophores derived from thiophene moiety by the Vilsmeier reaction and Knoevenagel reactin with high yield(>80%). They have the same N-methyl-N-hydroxyethyl phenylamine as electro-donor, and different electro accepters, malononitrile, cyanoacetic acid, ethyl cyanoacetate, p-nitrobenzene, and 1-cyanomethyl-4-nitrobenzene and 2-(3,5,5-trimethylcyclohex-2-enylidene) malononitrile. They have been confirmed and characterized using IR, 1HNMR, HPLC-Ms, et al. Their UV-Visual spectrum showed that they have maximum absorption in the range of 400-600nm. Studys with DSC, TGA can be included that they all have good thermal stability and high decomposition temperature, respectively. The non-linear optical properties of the chromophores are studied using solvatochromic method(SC) and Disenty Functional Theory(DFT), the results indicated that they all have large first-order hyperpolarizabilities(β0), some of them are even upto 550×10-30esu . Their second-nonlinear optical (NLO) response of doped and poled polymethyl methacrylate (PMMA) films were measured with simple-reflection technique at 1.3μm, and exhibit large electro-optical (E-O) coefficient (r33 >30pm /V).In chapter 3, The alkoxysilane functionalized chromophores were synthesized by coupling with isocyanatopropyltriethoxysilane (ICTEOS), and their matrix hybrid materials have been fabricated via sol-gel methodology copolymerized with tetraethyl orthosilicate (TEOS). The resulting hybrids exhibit good solutability in usual solvent, which offers ease of processibility in the preparation of sol-gel hybrid films. Their properties were fully characterized by Atomic force microscopy (AFM), UV-vis absorption spectroscopy and thermogravimetric analyzer (TGA). The results indicated that the hybrid films have high thermal stability and glass-transiton temperatures(Tg). The electro-optical (EO) coefficient (r33) of 10-20 pm/V have been obtained using simple reflection technique. This film exhibits excellent thermal stability of dipole alignment at elevated temperature. The r33 value has an onset temperature around 120℃, and remains at 95% of its initial value after heating at 80℃for 50 hours.In chapter 4, A series of novel spinle-like chromophores with high hyperpolarizabilities, based on 2,5-diphenyl-1,4-distyrylbenzeneπ-conjugating bridge, N,N-dimethyl and triphenyl amino donors, and Tricyano -vinyldihydrofuran(TCF), 1,3,3-trimethyl-5-dicyanovinyl-1-cyclohexene (TDC) acceptors, have been designed and synthesized successfully for the first time. The moieties on the 2,5-positions of theπ-conjugaters were varied to be thienyl, 4-methoxyphenyl and 4-trifluorophenyl in order to study the substituted effect on their linear and nonlinear optical properties. They were fully characterized by NMR, FT-IR, elemental analysis, and differential scanning calorimeter (DSC) methods. These chromophores have good thermal stabilities, some of them even exhibit the highest decomposition temperature(Td>375oC) to the best of our knowledge. And the nonlinear optical properties were evaluated theoretically(densitiy functional theory, DFT) in addition to recording relevant thermal data. The results show that, the hyperpolarizability of the chromophores exhibit the same trends with the increase of the withdraw ability of the substitutent group on theπ-conjugating bridge, one of the chromophores exhibit very largeβvalue (823×10-30esu). An up to 60nm blue-shift is realized as theπ-conjugating bridge changed from 1,4-distyrylbenzene to 2,5-diphenyl-1,4-distyrylbenzene. These results had shown that these chromophores have a great potential for the application of nonlinear optical materials.