Preparation And Properties Of Semiconductor Nanocomposites ZnS/PMMA Based On The "Diels-Alder" Reversible Reaction With High Thermal Stability Of Cross-linking Of Electro-optic Polymer

Organic second-order nonlinear optical (NLO) materials have been intensively studied in the past decade and made a great progress. Just to referring to the nonlinear response, the electro-optic (EO) coefficient value of the polar polymer which has been synthesized had already gone beyond higher than the number which inorganic crystal could obtained. For example, to the LiNbO3 crystal which had been applied for the EO modulator device and its EO coefficient r3 3got about 32pm/V. Compared with it, the organic polar polymer which had been reported by Dalton and Alex research group could achieve to 200pm/V. So the organic polar polymer materials had possessed the potential application ability to take the place of inorganic crystal. However it deserved to be specially noted that though the macroscopic EO activity had already worked out satisfactorily, to obtain a device-quality material the organic polymer materials should be satisfied with the strict requirement of high thermal stability of poling induced EO activity and the low optical loss beside the large EO coefficient.At the present time to achieve the purpose of thermal stability of poling-induced chromophore dipole alignment, the most commonly used solution was highly desirable to covalent incorporation of functionalized NLO chromophore into polymer systems and hardened through heat crosslinking reactions which caused the materials glass temperature improved. However, in the traditional chromophore-polymers systems, the lattice-hardening and poling process are often proceed together. With the increase of the temperature, the cross-linking rigidity of polymer is strengthened. But the poling ability of chromophore in the matrix become difficult as the lattice-hardening, what is called"nonlinearity-stability tradeoff".To solve the"nonlinearity-stability tradeoff", in this thesis we studied the"Diels-Alder"[4+2] cycloaddition reaction to realize the poling efficiency without compromise the lattice hardening. And the main work is as follow: (1) Based on the study of international research achievement, two new type of azo chromophore owned the main structure-triphenylamine as the donor were designed and synthesized. Both of them had not been reported in literatures. One of them was measured the EO coefficient ( r3 3) by simple reflection method.(2) Designed and synthesized a new type side-chain polymer system based on the"Diels-Alder"[4+2] cycloaddition crosslink contain dienophile a furan-capped maleimide and diene furan-3-carboxylic acid. They are attached onto the poly (4-vinylphenol) backbone as side chain to afford the cross-linkable NLO polymers. By control the temperature can realized whether lattic-hardening or not. The retro-DA would happen at the temperature 150℃and at the condition the chromophore in the matrix was orientated efficiently in the electric field. After the poling procedure finished, the temperature dropped to about 60℃, the DA reaction happened and the polymer lattice would harden and preserve the chromophore thermal stability. TGA and DSC research the process carefully.(3) Making use of the DA reaction to realize the purpose of covalent incorporation of functionalized NLO chromophore into polymer systems. Compared with the conventional covalent incorporation methods, such as azo coupling, kneovengel condensation or catalyzed esterification, by DA reaction no catalyst required that made the materials more pure and it quantitative conversion with minimum byproducts and the reaction conditions was mild. What's the important was we could control randomly the content of chromophorre in the polymer matrix as we needed.(4) According to the reported while F atom substituted the H atom, the material optical loss caused by C-H bond vibration would lower, especially in the communication wavelength 1310nm and 1550nm. Based on this result, we synthesized 3,5-bis(perfluorobenzyloxy)benzoic acid and they are attached onto the poly (4-vinylphenol) backbone contain dienophile a furan-capped maleimide as side chain which possess of high decomposition temperature. The decomposition temperature was 310℃. (5) Dendrimer was a relatively new class of macromolecules and was different from the conventional linear, crosslinked or branched polymer. The large dendron-chain could decrease the static interaction between chromophore effectively. To get to a dendrimer the chromophore should contain active multi-function group. Firstly designed and synthesized a new thiopheneπ-conjugate bridge which contained two -OH group: 2, 2'-(thiophene-3, 4-diylbis (oxy)) diethanol. And it provided a new avenue to achieve the dendrimer purpose.The major work as follow (The second part):(1) Found the ZnCl2 had a good solubility in the methyl methacrylate (MMA) in the condition of a little the methacrylic acid being exist. Pro-polymerization method preparation the ZnS/PMMA nanocomposite materials. And it was found the materials can have the high transparency by controlled the H2S reaction time.(2) Synthesize the polymer of Zn(MA)2 (ZnP). Prepared the ZnS/PMMA materials by swelling methods respectively through the mixture of ZnP/MMA and the mixture ZnCl2/MMA. The UV-vis spectrum was used to research the ZnS growth process in the matrix. In the comparison with the pro-polymerization, the swelling method was more favorable to the conversion of the Zn2+ ion. On the other hand it was not only had the higher converseon efficiency than ZnP but also more rapidly speed when using the ZnCl2 as the Zn2+ source.