【作者】 韩金；

【导师】 郑思珣；

【作者基本信息】 上海交通大学 ， 材料学， 2009， 博士

【摘要】 环形齐聚倍半硅氧烷(macrocyclic oligomeric silsesquioxanes, MOSS)是一类具有立体环状结构的齐聚倍半硅氧烷。其无机性质与多面体齐聚倍半硅氧烷(polyhedral oligomeric silsesquioxanes, POSS)类似,具有倍半硅氧烷骨架。MOSS可以具有不同Si-O单元数,并且具有广泛的可功能化特性。与POSS的合成相比,MOSS的合成具有方法简单,周期短,产率高的特点,并且对溶剂和环境的干燥程度要求较低。过去对这一类型齐聚倍半硅氧烷合成报道并不多见,对其官能化和应用方面的研究更是几无报道。本论文工作,研究了一系列MOSS的合成及官能化,并将它们用于无机/聚合物复合材料的制备。1.通过金属诱导自组装成环方法与一氢二甲基一氯硅烷的硅醚化反应合成了可自聚合的大环低聚倍半硅氧烷MOSS单体。在Karstedt催化剂存在下,实现了硅氢化加成聚合,得到了多孔性的聚倍半硅氧烷材料。研究结果表明MOSS环的尺寸极大地影响材料的多孔性。2.将含有十二个Si-H键的甲基十二元环MOSS与2-溴代异丁酸烯丙酯或2-氯丙酸烯丙酯进行硅氢化加成反应,成功得到了两种多官能度的原子转移自由基聚合(ATRP)引发剂。采用含十二个2-溴代异丁酸酯基的MOSS引发剂,在CuBr/PMDETA络合物催化下实现了丙烯酸叔丁酯的活性自由基聚合,接着在甲酸中水解,成功制备了两亲性的十二臂的聚丙烯酸“环刷”状聚合物。由于疏水的MOSS大环的存在使得该“环刷”状聚合物具有典型的两亲性,它们在水溶液可以组装成一系列“花”状的纳米结构,并具有不同的pH响应性,取决于每臂聚丙烯酸的链长。采用含十二个2-氯丙酸酯基的MOSS引发剂,在CuCl/Me6Tren催化下成功制备了两亲性的十二臂的聚异丙基丙烯酰胺“环刷”状聚合物。运用动态激光光散射方法研究这一类“环刷”状的聚异丙基丙烯酰胺在水溶液中的自组装行为和温度响应性。研究结果表明体系自组装行为和温度响应性具有极大的分子量依赖性,MOSS环的存在对聚异丙基丙烯酰胺链的构象变换具有阻碍作用。3.合成了六乙烯基六苯基的MOSS,并通过巯基-乙烯基(thiol-ene)点击化学反应(click chemistry)合成得到了含六个伯醇羟基的大分子引发剂,在辛酸亚锡催化下聚合己内酯,得到含有六臂聚己内酯的聚合物。将不同分子量的聚合物分别与α-CD络合得到超分子络合物。NMR氢谱表征结果说明当PCL臂长减短的时候,CL:α-CD络合比升高。这是由于MOSS大环存在位阻使靠近环的链段不易发生络合。依据同样方法,我们又合成了十二乙烯基十二三甲基硅基的MOSS,并加成巯基乙醇得到含十二个伯醇羟基的大分子引发剂,在辛酸亚锡催化下聚合己内酯,得到含有十二臂聚己内酯的环刷状聚合物。将不同分子量的聚合物分别与α-CD、γ-CD络合得到超分子络合物。NMR氢谱表征结果说明当PCL臂长减短的时候,CL:CD络合比升高。这是由于MOSS大环存在位阻使靠近环的链段不易发生络合。4.合成了带有乙烯基的MOSS分子,利用巯基-乙烯基(thiol-ene)点击化学反应(click chemistry)合成了含十二羟基与十二羧基的MOSS,研究了这两种功能化的MOSS与聚氧化乙烯(PEO)的相容性及分子间特殊相互作用。研究结果表明MOSS与高分子之间的相容性极大地取决于复合体系的分子间特殊相互作用,只有在有利的特殊相互作用存在条件下才能够通过物理混合的方法制备有机/无机纳米复合材料。5.利用硅氢化加成方法合成了一系列含环氧基的MOSS,将这些功能化的MOSS成功地引入热固性聚合物体系中,成功地制备了含MOSS的热固性环氧树脂和苯并噁嗪树脂纳米复合材料。运用动态力学分析(DMA)研究了这一类复合材料的所得材料的粘弹性行为,用热重分析(TGA)研究了材料的热稳定性。更多还原

【Abstract】 Macrocyclic oligomeric silsesquioxanes (MOSS) are a novel class of silsesquioxanes with unique stereo cyclic structures. They have silsesquioxane frameworks and their inorganic properties are similar to POSS (polyhedral oligomeric silsesquioxanes) molecules. MOSSs have different numbers of Si-O repeat unit, and their functionalizations are very rich. Compared to the preparation of POSS, the preparation of MOSS is more convenient, short-term, high-yield and its need for dryness of solvents and environment is low. In the past, there are some literatures concerning the preparation of MOSS; however, there are few reports on functionalization and application of MOSS. In this contribution, a series of MOSS were prepared, functionalized, and then employed to prepare inorganic/polymer composites.1. Two self-polymerizable MOSS molecules were prepared via metal directed self-assembly and silylation with hydrodimethylchlorosilane. The hydrosilylative polymerizations were carried out with Karstedt catalyst and afford porous polysilsesquioxane material. It is suggested that the size of MOSS significantly influence the porosity.2. 12-membered MOSS containing reactive Si-H groups was modified with allyl 2-bromoisobutyrates and allyl 2-chloroisopropyrates via hydrosilylation reaction to generate two types of ATRP initiators. The former one was employed in ATRP polymerization of tert-butyl acrylates under CuBr/PMDETA catalyst and the obtained MOSS-PtBA hybrid brushes were hydrolyzed to amphiphilic MOSS-poly(acrylic aicd) brushes in formic acid. The MOSS-PAA brushes can assemble into a series of flower-like nanostructures and have different pH responsibilities. The latter one was employed in ATRP polymerization of N-isopropylacrylamide under CuCl/Me6Tren catalyst and generated amphiphilic 12-arm PNIPAM cyclic brushes. The self-assembly and temperature responsibility was investigated using dynamic laser scattering analysis. It is revealed that the self-assembly and temperature responsibility depend on the molecular weight significantly. The presence of MOSS restricts the reverse of conformation of PNIPAM chains.3. MOSS molecule containing six vinyl groups were prepared and carried out thiol-ene reaction with 2-mercaptoethanol to generate initiator with six primary hydroxyl groups. The initiator was used in polymerization ofε-caprolactone with Sn(Oct)2 catalyst to generate six-arm poly(ε-caprolactone). The brushes with different molecular weight were threaded intoα-cyclodextrins to generate supramolecular complexes. NMR results indicated that when the arm length decreased, the mole ratio of CL: CD would increase. It is judged that the topology and bulk MOSS cause difficulty on supramolecular complexation of CDs with PCL segments near the MOSS core. In the same way, MOSS molecule containing twelve vinyl groups was prepared and carried out thiol-ene reaction with 2-mercaptoethanol to generate initiator with twelve primary hydroxyl groups. The initiator was used in polymerization ofε-caprolactone with Sn(Oct)2 catalyst to afford 12-arm poly(ε-caprolactone). The brushes with different molecular weight were threaded intoα- orγ-cyclodextrins to generate supramolecular complexes. NMR results indicated that when the arm length decreased, the mole ratio of CL: CD would increase. It is judged that the topology and bulk MOSS cause difficulty on supramolecular complexation of CDs with PCL segments near the MOSS core.4. MOSS molecules containing twelve hydroxyl or carboxyl groups were prepared via thiol-ene reaction with 2-mercaptoethanol or 3-mercaptopropylic acid, respectively. The miscibility and the special interaction between these two MOSSs and PEO were investigated. It is suggested that the miscibility significantly depends on the special interaction, and only if enough strong special interaction presents, it will be able to prepare organic-inorganic nanocomposites via physical mixing. 5. A series of MOSS molecules containing epoxy groups were synthesized by hydrosilylation reaction with allyl glycidyl ether and introduced into epoxy thermosets and polybenzoxazine thermosets, respectively. The viscoelastic behaviors were studied by dynamic mechanic analysis experiments, and the thermal stabilities were investigated by thermogravimetric analysis.更多还原