【作者】 谢建达；

【导师】 施文芳；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2008， 博士

【摘要】 近三十年来,有机聚合物非线性光学材料因具有非线性系数高、响应快、带宽大、结构可设计、易加工等优点,在信息领域显示出极大的应用潜力而得到广泛重视。为了达到制备电光设备的实用要求,非线性光学材料必须同时具备较大的光学非线性、优异的取向稳定性、较低的光学损耗和良好的可加工性能。如何使含高一阶超极化率的发色团的聚合物中具有优异的二阶非线性光学性能是人们在优化材料时遇到的主要问题之一。然而发色团偶极间的静电相互作用是影响聚合物非线性光学性能的主要因素之一。最近的理论研究发现,如果使用近似球形或压扁的椭球形分子,可以有效减少发色团之间的接近程度及其相互作用,从而获得更大的二阶非线性光学系数。超支化聚合物是一类高度支化的聚合物,具有不规则的三维准球形结构、大量的分子内孔隙、良好的溶解性、较低的黏度等特殊的物理化学性质,而且它易于合成,可通过一步法制备得到。这些特殊性能为超支化聚合物在非线性光学材料领域中的应用提供了可能。本论文以获得具有高宏观二阶非线性光学活性及热稳定性的聚合物材料为目的,制备了一系列可交联型超支化极化聚合物材料,并对其各项性能进行了研究。一、“A₂+B₃”缩聚法合成超支化聚苯甲酸酯及其二阶非线性光学研究以DR19为A₂单体,以1,3,5-苯三甲酰氯为B₃单体,以三乙胺为吸酸剂,采用“A₂+B₃”溶液缩聚的方法制备了超支化聚苯甲酸酯,并分别用甲醇和缩水甘油对超支化聚合物进行封端。通过核磁共振、红外光谱、凝胶渗透色谱、紫外可见吸收光谱等方法对所得聚合物进行了表征;采用差热分析、热重分析等方法研究聚合物的热性能;用二次谐波产生法研究聚合物的非线性光学性能,其二次谐波系数大于51pm/V,且二次谐波系数起始衰减温度高于130℃。研究表明,用环氧基团封端的超支化聚苯甲酯具有更好非线性光学热稳定性。二、“click”反应“A₂+B₃”缩聚法合成超支化聚三唑以4 4-{N,N’-二（3-叠氮基丙基）氨基}-4’-硝基偶氮苯为A₂单体,1,3,5-三（炔丙氧基）苯为B₃单体利用铜催化环加成反应通过“A₂+B₃”的聚合方式合成了可溶性超支化聚三唑。探讨了催化剂浓度、单体浓度及其投料方式、反应时间等对反应进程以及超支化聚三唑分子结构的影响;通过核磁共振、红外光谱、凝胶渗透色谱、紫外可见吸收光谱等方法对所得聚合物进行了表征,利用NMR法测定超支化聚三唑的支化度在0.45-0.58之间;采用差热分析、热重分析等方法研究超支化聚三唑的热性能。三、“click”反应合成超支化聚三唑及其二阶非线性光学研究利用“点击”反应,通过“A₂+B₃”缩聚法设计合成了外围带炔基的超支化聚三唑;为了比较,合成了对应的线性聚三唑。通过核磁共振、红外光谱、凝胶渗透色谱、紫外可见吸收光谱等方法对所得聚合物进行了表征;采用差热分析、热重分析等方法研究聚合物的热性能。采用二次谐波产生法研究了聚合物的非线性光学性能,超支化和线性聚三唑极化膜在1064nm波长处的二次谐波系数d₃₃分别为96.8和23.5pm/V,相应的二次谐波系数起始衰减温度分别为165和123℃,表明超支化聚三唑具有更优异的非线性光学性能及热稳定性。更多还原

【Abstract】 Due to high nonlinear coefficient, short response time, large operational bandwidth, ease of processing, low dielectric constant, polymeric nonlinear-optical materials have received considerable attention in the past 30 years for their potential applications in photonics. One of the main challenges still facing in this field is how to effectively translate high molecular optical nonlinearities of chromophores into large macroscopic electro-optic （EO） coefficients and maintain good temporal stability. The involved problem is that the chromophoric aggregation resulted from strong intermolecular electrostatic interactions often quenches the EO activity. The recent theoretical analyses suggest that, due to the steric effect, the spherical molecular shape can minimize the intermolecular electrostatic interaction, resulting in maximum macroscopic nonlinearity. Hyperbranched polymers are globular macromolecules, can thus minimize the intermolecular electrostatic interactions with their site-isolation effect, and optical loss in the NLO process with their large void-containing highly branched structure. Moreover, hyperbranched polymers are easy to synthesize via "one-step" approach. Hyperbranched polymers, therefore, are promising candidates for NLO materials with good macroscopic EO activity. To develop NLO polymers with high macroscopic nonlinearity and thermal stability, in this thesis, a series of NLO hyperbranched polymers were designed and synthesized. Their NLO properties were investigated.1. Synthesis and nonlinear optical properties of NLO hyperbranched poly（aryl ester）sTwo hyperbranched poly（aryl ester）s with methyl ester （P1） and epoxy （P2） terminal groups containing pendant azobenzene chromophores were prepared through an "A₂ + B₃" approach used for second-order nonlinear optical materials. Their chemical structures were characterized by NMR and GPC analysis. The polymers have good solubility in common organic solvents and film-forming ability. The pure films were fabricated successively without doping into other matrices. The poled films exhibit high second-harmonic-generation coefficients （> 50 pm/V） due to the three-dimensional spatial isolation effect resulting from their highly branched structures. The optical nonlinearity of the poled P2 film is more thermally stable than that of P1 due to the cross-linking of epoxy groups with carboxylic acid groups in the former during poling. The onset decay temperature of SHG intensity of P2 was determined to be around 155℃, which was 20℃higher than that of P1.2. Synthesis and Characterization of Hyperbranched Polytriazole via an "A₂ + B₃" Approach Based on Click ReactionThe hyperbranched polytriazole （hb-PTA） was synthesized through "A₂ + B₃" approach using "click reaction". 4-N,N’-dis（2-azidoethyl）amino-4’-nitro-azobenzene and 1,3,5-tris（alynyloxy）benzene were synthesized to be used as A₂ and B₃ monomer, respectively. The polymerization was carried out via "one-pot" and "slow-addition" methods. The obtained hb-PTA was soluble in common organic solvents. The molecular structure was characterized by ¹H NMR, FTIR, and GPC. The degree of branching of hb-PTA was determined to be around 0.50. The obtained hb-?TA exhibits high thermal stability.3. Synthesis and nonlinear optical properties of hyperbranched polytriazole containing second-order nonlinear optical chromophoreThe hyperbranched polytriazole （hb-PTA） containing second-order nonlinear optical chromophore was synthesized through "A₂ + B₃" approach based on "click reaction". Its corresponding linear analogue （l-PTA） was prepared for comparison. The hb-PTA has better solubility in common organic solvents than the l-PTA. Both the polymers exhibit good thermal stability with 5% weight loss temperatures over 260℃. The poled film of hb-PTA exhibits much higher second-harmonic coefficient （96.8 pm/V） than that of l-PTA （23.5 pm/V）. The onset decay temperature of SHG intensity of hb-PTA was determined to be around 165℃, which was 42℃higher than that of l-PTA. The three-dimensional spatial isolation effect resulting from the highly branched structure and the cross-linking of the terminal acetylene groups at moderate temperature play important roles in the enhancement of optical nonlinearity.更多还原