【作者】 许栩；

【导师】 朱秀林；

【作者基本信息】 苏州大学 ， 高分子化学与物理， 2010， 硕士

【摘要】 偶氮苯聚合物既具有偶氮苯基团的光致顺反异构化特性,又具有高分子材料优异的力学性能和加工性能,在液晶材料、光信息存储材料及非线性光学材料等许多领域都具有广泛的应用。环型聚合物因为没有端基所以表现出与相同分子量的线型聚合物不同的性质,例如溶液性质、结晶性质和热性能等。因此,探索并设计具有新颖结构和优异性能的环型偶氮苯聚合物成为高分子化学和材料领域的重要课题之一。本论文主要设计并合成了两种结构新颖的环型偶氮苯聚合物,并与线型聚合物前体进行对比,研究了环型聚合物的性能。研究内容具体包括:(1)首先利用热催化1,3-偶极环加成方法对单体3’-炔基-[4-己氧基-(2-叠氮基-2-甲基丙酸酯基)苯基]偶氮苯(EHPA)进行逐步聚合,得到端基分别为叠氮基和炔基的线型主链偶氮苯聚合物linear-PEHPAs,然后采用高效“Click”化学首尾相接分子内成环反应成功合成环型主链偶氮苯聚合物cyclic-PEHPAs。由于线型聚合物前体几乎百分之百的端基功能化度,所以分子内环化反应的产率高达70%。利用核磁共振(1H NMR)、凝胶色谱(GPC)、红外光谱等测试手段对聚合物进行了结构表征,确认了所得聚合物的环型拓扑结构。环型聚合物cyclic-PEHPAs由于没有链端基,所以与其线型聚合物前体linear-PEHPAs相比具有较高的玻璃化转变温度。环型聚合物的分子量越小,即环越小,比相同分子量线型聚合物的玻璃化转变温度高得越多。线型和环型主链偶氮苯聚合物都显示了高的热稳定性(热分解温度高于320 oC)。环型聚合物与其相应的线型聚合物前体在几乎相同的温度表现出5%的热失重,但随着失重量的增加,环型聚合物对应的热失重温度与线型聚合物相比呈逐渐升高的趋势。分子量较小的聚合物cyclic-PEHPA2和linear-PEHPA2因为较低的聚合度所以其耐热性没有分子量较大的聚合物(cyclic-PEHPA1和linear-PEHPA1)的耐热性好。对线型和环型偶氮苯聚合物紫外光照反-顺异构化和可见光照射顺-反异构化性能的研究,发现分子量较小环型聚合物cyclic-PEHPA比对应的线型聚合物linear-PEHPAs具有更快的异构化性能。但是随着分子量变大,这种差异变小。(2)合成了含α-叠氮基团和ω-炔基的偶氮苯ATRP引发剂2-溴-2-甲基丙酸-4-(4-丙基-2-炔基氧基偶氮苯基)苯酯(2-Bromo-2-methyl-propionic acid 4-(4-prop-2-ynyloxy-phenylazo)-phenyl ester, BMPAPE)。以BMPAPE为ATRP引发剂,常温下进行异丙基丙烯酰胺(NIPAM)的活性聚合,制备线型聚合物linear-azo-PNIPAM-Br,端基叠氮化得到聚合物linear-azo-PNIPAM-N3,然后在稀溶液中通过“Click”化学分子内成环的方法合成了主链上含单个偶氮苯基团的环状聚异丙基丙烯酰胺cyclic-azo-PNIPAM。对线型以及环型聚合物进行了核磁、红外、GPC等一系列表征,证实了环型偶氮苯聚合物的结构。对线型和环型偶氮苯聚合物紫外光照反-顺异构化性能的研究,发现环型聚合物cyclic-azo-PNIPAM相比于对应的线型聚合物linear-azo-PNIPAM-N3具有更快的光致异构化性能。更多还原

【Abstract】 Azobenzene polymers combine the unique optical trans-cis-trans isomerization behavior of azobenzene and the good processability and mechanical properties of polymer materials. These azobenzene polymers can be potentially applied in fascinating photo-responsive variations, such as liquid crystal displays, optical data storage, nonlinear optical materials and so on. Cyclic polymers have attracted more and more attentions in recent years due to their unique topological structures and characteristic properties in both solution and bulk state.Therefore, develop and design of new cyclic azobenzene polymers with the novelty structure and excellent optical activity has been an important assignment for polymer chemistry.In this thesis, we designed and synthesized two kinds of azobenzene polymers with the novel structures. Their trans-cis isomerization and so caused properties change were investigated. The detailed researches were summarized as the following:(1) Anα-azide,ω-alkyne A-B type azobenzene monomer, 3’-ethynylphenyl- [4-hexyl-(2-azido-2-methyl-propionate)phenyl]azobenzene (EHPA), was synthesized and used to generate PEHPA precursor(linear-PEHPA) via step-growth polymerization by thermal 1,3-dipolar cycloaddition in bulk. The subsequent end-to-end intramolecular coupling reaction under high dilution and“click”conditions leads to efficient preparation of cyclic-PEHPA. Gel permeation chromatography (GPC), 1H-NMR and Fourier transform infrared (FT-IR) spectra all confirmed the complete transformation of linear-PEHPA to cyclic-PEHPA.Because of the absent chain ends, the cyclic-PEHPAs showed higher glass transition temperatures than the linear-PEHPAs with the same molecular weight. But this difference increased with decreasing molecular weight of the polymers. The decomposition temperatures (Tds) of cyclic-PEHPAs and the corresponding linear-PEHPAs were almost the same, and thermally stable up to 320oC under nitrogen atmosphere. However, at higher temperatures, the decomposition of the cyclic ones proceeds more slowly than the linear ones. Furthermore, the photoisomerization of trans–cis and cis–trans recovery of the linear-PEHPAs and cyclic-PEHPAs in DMF were investigated by irradiation with UV light and visible light, respectively. Comparing with the precursor linear-PEHPAs, the cyclic-PEHPAs have shown a little faster trans-cis-trans photoisomerization ability. These intriguing results obtained from photoisomerization of cyclic main-chain azobenzene polymers are worthy of further theoretical considerations.(2) We report on the preparation of well-defined cyclic azobenzene poly(N-isopropylacrylamide) (cyclic-azo-PNIPAM) via ATRF and click chemistry. A novel ATRP initiator bearing with azobenzene and alkyne groups, 2-Bromo-2-methyl-propionic acid 4-(4-prop-2-ynyloxy-phenylazo)-phenyl ester (BMPAPE), was synthesized and successfully used as the ATRP initiator to initiate the polymerization of N-isopropylacrylamide (NIPAM). Then linear-azo-PNIPAM-Br reacted with NaN3 to transform the terminal chloride into azide group to get linear-azo-PNIMA-N3. The subsequent end-to-end intramolecular coupling reaction under high dilution and“click”conditions leaded to efficient preparation of cyclic-azo-PNIPAM. GPC, 1H-NMR and FT-IR spectra all confirmed the complete transformation of linear-azo-PNIPAM-N3 to cyclic-azo-PNIPAM. Comparing with the linear-azo-PNIMA-N3 with the same molecular weight, the cyclic-azo-PNIPAM have shown a little faster trans-cis photoisomerization ability.更多还原