【作者】 朱维菊；

【导师】 徐洪耀；

【作者基本信息】 安徽大学 ， 无机化学， 2010， 博士

【摘要】 近年来,具有较大双光子吸收截面的有机共轭材料在三维光信息存储、双光子荧光显微和成像、频率上转换激射、光学微加工、光限幅以及光生物学等方面显示出的良好应用前景,使得设计合成综合性能优良的有机双光子材料越来越受到人们的重视。现有的有机双光子吸收材料存在着一些不足,如：热性能好且双光子吸收截面大的材料较少；分子结构和双光子吸收性能之间的关系还不完全清楚;高分子双光子材料的品种研究较少等。因此,如何推动双光子吸收材料的实用化进程,研制出综合性能良好的双光子吸收材料是各国研究者们密切关注的焦点问题。偶氮苯、二苯乙烯及其芴类衍生物作为有机光电材料已被广泛的应用在非线性光学、光开光、光存储、光限幅及液晶等研究领域。为了改善有机小分子双光子材料的实用性能,我们设计合成了一系列含有偶氮苯和二苯乙烯非线性生色团的末端炔功能性单体,然后将这些末端炔有机共轭小分子单体以[Rh(nbd)Cl]2为催化剂通过均聚反应引入高分子体系,合成了一系列含有偶氮苯和二苯乙烯的长共轭侧链的聚炔共轭高分子,并详细探讨了材料结构与双光子吸收性能间关系。主要工作内容如下：1.简述了双光子吸收的原理及双光子吸收截面的测试方法,详细介绍了双光子吸收材料的研究进展,并针对材料研究与应用中存在的不足,提出课题研究内容。2.以[Rh(nbd)Cl]2-Et3N为催化剂,成功的将含长共轭链的偶氮炔化合物进行聚合,合成了含不同末端取代基长共轭侧链的溶解性及热稳定性较好的聚炔共轭高分子。对聚合物的热性能研究发现,引入刚性的偶氮苯基团到聚炔中赋予聚合物良好的热稳定性,其热稳定性的增加是由于芳香的生色团侧链的“夹克效应”导致的。利用Z-扫描技术,在450 fs脉宽,780 nm波长条件下测试了三种聚合物的双光子吸收截面(σ2)分别为659、1 220和2040 GM。双光子吸收截面和光限幅性能研究的结果显示,偶氮侧链生色团的引入赋予了功能聚炔高分子较大的双光子吸收截面、较好的光限幅性能和良好的光稳定性。它们的非线性光学性能受到分子结构的影响明显,与侧链具有吸电子基团NO2的偶氮苯聚炔相比,含供电子的CH3结构及未取代的H显示了较小的双光子吸收截面以及较差的光限幅性能,主要是由于吸电子基团的引入增加了共轭链的有效长度,从而使分子的双光子吸收性能增强。光限幅机理可能主要来自于分子的双光子吸收。3.以[Rh(nbd)Cl]2-Et3N为催化剂,成功的将含长共轭侧链的苯乙烯功能基团进行聚合,合成了含不同末端取代基的长共轭侧链的溶解性及热稳定性好的聚炔共轭高分子。聚合物的固体荧光测试显示,荧光强度与激发光强之间的近二次方关系,表明该过程中的荧光发射是由双光子吸收引起的。利用Z-扫描技术,在450 fs脉宽,780 nm波长条件下测试了三种聚合物的σ2分别为644、909和1140GM。结果表明侧链含有硝基取代基聚合物的σ2大于含有甲基及未被取代的聚合物的σ2,造成这种差异主要是由于在含有硝基的侧链中含有吸电子取代基使得共轭体系中有更多的电子参与共轭增加了共轭链的有效长度,从而使离域强度增强。光限幅测试结果表明目标聚合物具有较好的光限幅性能,且聚合物的光限幅性能优劣性和σ2一致,这主要是由于在含有硝基的侧链中分子结构具有最大的电子离域效应引起的,光限幅的机理可能主要来自于分子的双光子吸收。4.以[Rh(nbd)Cl]2-Et3N为催化剂,成功的将含长共轭侧链的含有芴基的苯乙烯及偶氮苯功能基团进行聚合,合成了含不同共轭桥末端为芴取代基团的长共轭侧链的溶解性及热稳定性好的聚炔共轭高分子。结果显示芴基上引入柔性的烷基链有效的提高了聚合物的溶解性。对聚合物的热性能研究发现,引入不同共轭桥末端为芴取代基团的长共轭侧链到聚炔中赋予聚合物良好的热稳定性,其热稳定性的增加是由于芳香的生色团侧链的“夹克效应”导致的。聚合物的固体荧光测试显示,荧光强度与激发光强之间的近二次方关系,表明该过程中的荧光发射是由双光子吸收引起的。采用Z-扫描技术,在450 fs脉宽,780 nm波长条件下测得两种聚合物的σ2分别为2010和3950 GM。结果表明含N=N共轭桥的σ2大于含C=C共轭桥的,造成这种差异的主要原因是含有偶氮侧链中由于偶氮基团中有更多的电子参与共轭,使π共轭程度升高、π电子云密度增加,离域强度增强,从而使其共轭双键体系增大,即电荷能在其中进行更好地转移。光限幅测试结果表明两种聚合物具有较好的光限幅性能,且含有偶氮芴基侧链的聚合物光限幅性能优于含苯乙烯共轭桥侧链的,这主要是由于前者的分子结构具有较大的电子离域效应引起的,光限幅的机理可能主要来自于分子的双光子吸收。5基于Schweig非线性光学的理论,二阶非线性有机生色团可有效提高共轭高分子的三阶非线性光学性能,我们通过分子设计将二阶非线性系数较大的偶氮苯、二苯乙烯和芴基生色团连接到共轭聚炔高分子中,增加材料的非线性,并期望产生新颖的非线性光学性能。我们设计合成了含不同的末端取代基相同共轭桥及相同的末端取代基不同共轭桥的长共轭侧链的共轭聚炔高分子双光子材料,分别研究了分子结构的不同对它们的热稳定性、双光子吸收及光限幅性能的影响。该研究不仅丰富了功能聚炔衍生物体系,而且为可溶、高热稳定新型高分子双光子材料的分子设计奠定基础。更多还原

【Abstract】 There is still a growing interest in organic compounds with large two-photon absorption (TPA) cross-section and excellent up-conversion emission properties due to their potential for application in a wide range of areas such as frequency-up-converted lasing,3-D optical data storage, lithographic micro fabrication, optical-limiting, etc. The existing organic TPA materials still have some shortages, such as low thermal stability and small TPA cross-section; the relationship between molecular structure and TPA property is still not clearly understood; there are some difficulties in synthesizing new polymer TPA materials. Therefore, it’s very important to explore new TPA materials with large TPA cross-section, good comprehensive performance. Azobenzene, stilbene, fluorene and its derivatives possessing longπ-electron conjugated structure have been widely used in nonlinear optics, optical storage, light opening, optical limiting and LCD areas. In order to meeting the requirements of practical applications, stilbene, azobenzene and fluorene were used as NLO chromophores, we designed and synthesized series of conjugated polyacetylenes containing azobenzene, stilbene and fluorene NLO chromophores, respectively, and investigated the relationships between the molecular structure and TPA properties. The main contents consist of the following points:1. The principle of TPA and the testing methods of TPA cross-section and their recent development were systematically reviewed. Based on the existing problems in research and application, the contents of our research were put forward.2. A series of polyacetylene with different functional groups of azobenzene were designed and synthesized by [Rh(nbd)Cl] 2-Et3N. It was found that introduction of azobenzene chromophore pendants effectively increase the thermal stability and TPA cross-section properties of resulting polyacetylenes and endowed the polyacetylenes with novel OL properties. TPA absorption cross section (σ2) were 659, 1 220 and the 2 040 GM by using Z-scan technique, in 450 fs pulse width,780 nmwavelength. The TPA and OL properties were significantly affected by molecular structure, the polyacetylenes having strong acceptor (NO2) as a terminal group exhibites largeσ2 and well OL properties. The OL mechanism may be mainly originated from TPA of molecules.3. A series of polyacetylene with different functional groups of styrene were designed and synthesized by [Rh (nbd) Cl]2-Et3N. It was found that introduction of styrene chromophore pendants effectively increase the thermal stability and TPA cross-section properties of resulting polyacetylenes and endowed the polyacetylenes with novel OL properties. Linear dependence of solid fluorescence intensity on square of the excitation intensity confirms that fluorescence emission is originated from the TPA absorption mechanism. TPA absorption cross section (σ2) were 644,909 and the 1 140 GM by using Z-scan technique, in 450 fs pulse width,780 nm wavelength. The TPA and OL properties were significantly affected by molecular structure, the polyacetylenes having strong acceptor (NO2) as a terminal group exhibited largerσ2 and better OL properties, which is attributed to the largerπ-electron delocalization. The OL mechanism may be mainly originated from TPA of molecules.4. A series of polyacetylenes with the differentπ-electron conjugated bridge structure groups of fluorene were designed and synthesized by [Rh(nbd)Cl]2-Et3N as a catalyst. The results show that long flexible alky] chain increases the solubility and processablity of resultant polymers. It was found that introduction of fluorene chromophore pendants effectively increase the thermal stability and TPA cross-section properties of resulting polyacetylenes and endows the polyacetylenes with novel OL properties. Linear dependence of solid fluorescence intensity on square of the excitation intensity confirms that TPA is the main excitation mechanism of the intense fluorescence emission. TPA absorption cross section (σ2) were 2010 and the 3 950 GM by using Z-scan technique, in 450 fs pulse width,780 nm wavelength. The TPA and OL properties were significantly affected by molecular structure, the polyacetylenes with chromophore group of N=N double bond as conjugation bridge shows better TPA and OL performance than that with C=C asπ-conjugation bridge structure, which is attributed to the largerπ-electron delocalization. The OL mechanism may be mainly originated from TPA of molecules. 5. Based on Schweig’s nonlinear theory, the second-order NLO organic chromophore can effectively enhance the third-order nonlinear optical properties of the conjugated polymer, we designed three series of conjugated poly acetylenes containing large second-order NLO chromophores (azobenzene, stilbene and fluorene) and it was expected to obtain novel polymer two-photon materials. The results show that these compounds possess good optical limiting and largeσ2, which are attributed to the long D-π-A and D-π-D conjugated electron structure of molecules, and theπ-electron conjugated bridge structure or different terminal group affects the nonlinear optical and optical limiting properties of conjugation.compounds. The study not only enriches the functionalized polyacetylene derivatives, but also provides foundation for molecular design of novel soluble polymer two-photon materials with high thermal stability.更多还原