【作者】 刘磊；

【导师】 胡源； T.Richard Hull；

【作者基本信息】 中国科学技术大学 ， 安全技术及工程， 2007， 博士

【摘要】 倍半硅氧烷是指所有符合经验公式RSiO_1.5（这里R代表氢或任何烷基、烯基、芳基或有机功能取代的烷基、烯基、芳基）的有机无机化合物。因其具有特殊的微观结构、良好的热稳定性、优异的介电性能，同时还具有良好的反应可控性能，自上世纪六十年代以来被广泛研究。本文在大量文献调研的基础上，综述了梯形倍半硅氧烷和笼型倍半硅氧烷的合成、表征以及在复合材料中的应用，在此基础上，对于梯形倍半硅氧烷的合成、侧基聚合、真空炭化、有机改性作了一系列的研究；对比了有卤体系和无卤体系笼型倍半硅氧烷的对聚苯乙烯的阻燃性能的改善以及作用机制；合成了笼型倍半硅氧烷-表面活性剂的层状纳米杂化材料，尝试将其应用于聚苯乙烯复合材料，改善了复合材料的燃烧性能。归纳起来，本文的主要工作主要涉及以下几个方面：（1）关于梯型倍半硅氧烷的热稳定性能研究。采用小分子有机胺（正丁胺）作为模版，以逐步水解缩合的方式，合成乙烯基梯形倍半硅氧烷，对其结构和热性能行进表征；在乙烯基梯形倍半硅氧烷的结构基础之上，采用热催化聚合的方式，使其侧链乙烯基的同侧定向聚合，得到具有四条平行主链的硅氧碳氢聚合物，使用核磁共振氢谱、核磁共振碳谱、X射线衍射、红外光谱、扫描电镜和透射电镜对产物的结构、侧基聚合的机理进行了充分的表征和探讨。这种聚合物具有更高的热稳定性能，并对热稳定性提高的原因进行了解释。研究了侧链聚合的梯型倍半硅氧烷的高温真空炭化行为，根据XRD、质量变化和元素分析的结果，得出了700℃是该种物质从侧基降解失重到双链平行交联的转折温度；利用梯型硅氧烷高热稳定的这一特点，通过溶液插层和热（250℃）处理的办法，将耐高温的梯型结构大分子引入有机土中，替换其中的表面活性剂成份，得到具有更高热稳定性的倍半硅氧烷改性土。（2）四甲基铵笼型硅酸盐和溴化苯基笼型倍半硅氧烷的合成、表征及其聚苯乙烯复合材料的阻燃性能研究。使用正硅酸乙酯和四甲基氢氧化铵，采用水解缩合的方法制备笼型八（四甲基铵）八硅酸盐（TMN-POSS），将其作为聚苯乙烯（PS）树脂的添加剂，采用熔融共混的方法制备了TMN-POSS／PS复合材料。实验结果表明，20％和30％TMN-POSS／PS复合材料的热释放速率峰值比PS纯样分别下降31.7％和54.6％，平均值分别下降17.6％和41.5％；同时复合材料的燃烧过程中的CO释放速率峰值分别比纯的PS下降55.3％和66.1％，浓度也有相应规律的变化；CO₂浓度比PS纯样分别下降31.1％和62.0％；CO₂释放速率峰值分别下降23.8％和53.1％；20％和30％TMN-POSS／PS复合材料的氧指数从PS纯样的16.5分别提高到22和23。以苯基三氯硅烷为起始原料，通过水解缩合、催化重排的办法制备了八聚苯基笼型倍半硅氧烷（Ph-POSS），在Fe粉催化条件下将溴元素引入Ph-POSS的苯环得到Br-POSS；使用该种Br-POSS和Sb₂O₃的混合物（3∶1，质量比）作为聚苯乙烯（PS）树脂的添加剂，采用熔融共混法制备（Br-POSS+Sb₂O₃）／PS复合材料。实验结果表明，（Br-POSS+Sb₂O₃）的含量在15％以上时可以在聚合物中形成三维空间网络结构，这种分布的协效体系可以使得复合材料的热释放速率峰值从树脂纯料的900kW／m²以上降到200kW／m²以下，氧指数从16.5提高到29和30，达到UL-94 V0的阻燃标准。进一步的研究分析表明，POSS提高聚合物材料的阻燃性能主要取决于POSS本身核心笼型硅氧结构在材料燃烧中的阻隔作用、POSS有机取代基所包含的高效阻燃元素或基团、POSS在聚合物基体中的分散状况等因素。（TMN-POSS）／PS和（Br-POSS+Sb₂O₃）／PS两种复合材料燃烧性能提高的原因相同之处在都含有POSS笼型硅氧结构，而且POSS都能在聚合物基体中在纳米尺度上均匀分散；不同之处在于POSS的有机取代基团。（3）基于离子型笼型倍半硅氧烷—表面活性剂层状杂化材料的相关研究。一方面，使用多电荷阴离子的八磺酸根POSS和十六烷基三甲基溴化铵表面活性剂在水溶液体系里面进行离子交换反应，利用有机-无机不同的相似相容性质通过自组装的手段，得到具有规整的二维层状结构的杂化材料。通过X射线衍射、高分辨透射电镜和扫描电子显微镜等表征手段确定了这种层状结构的存在，而且确定了层间距在3～5nm之间；另一方面，使用多电荷阳离子的笼型八聚（γ-氯化氨丙基）POSS和十二烷基苯磺酸钠在水溶液体系里面进行离子交换反应，也可以得到类似的二维层状结构的杂化材料。实验研究表明，通过调整POSS和表面活性剂的物质的量比例可以改变片层结构，发现当POSS成分大大过量的时候，片层重复单元按照“烷基-POSS-POSS-烷基”顺序排列，对应较大的层间距；当表面活性剂成分大大过量的时候，片层重复单元按照“烷基-POSS”顺序排列，对应较小的层间距。另外，表面活性剂链长对材料层间距的影响，在POSS-表面活性剂比例相同的情况下（比如表面活性剂饱和POSS的情况），表面活性剂烷基链按照类似的方式排列，烷基链的长短（对于直链就是碳原子的个数）以近似线性的规律影响层状杂化材料的层间距。最后，使用这种杂化材料制备PS复合材料，初步对该种复合材料燃烧性能的初步研究表明，1％的添加量对于热释放速率的峰值就有较大的降低，降幅达到50.1％；当含量继续增加时，反而下降的数量并不明显。更多还原

【Abstract】 Silsesquioxanes are a large branch of organic-inorganic silicon-containing compounds. They can be represented as (RSiO_3/2)_n, where R can be hydrogen or any alkyl, alkylene, aryl, arylene groups, or organo-functional derivatives of them. Due to its special definite microstructure, good thermal stabilities, excellent dielectric properties, and ideal controllable performance in reactions, silsesquioxanes have attracted considerable research interests since 1960s. In this work, the general synthesis, characterization and applications of ladder-like and cage-like silsesquioxanes have been summarized on the basis of extensive investigation of literatures. The synthesis, side vinyl polymerization, carbonization in vacuum of ladder-like silsesquioxanes and its application in clay modification are studied; the combustion properties and fire retardant mechanism of halogen-free and halogen-containing polyhedral oligomeric silsesquioxanes （POSS）/Ploystrene（PS） system have been investigated and contrasted; POSS-surfactants lamellar hybrids were also prepared in this work, and were used as a special filler for PS in order to improve its combustion properties. In summery, this dissertation is composed of the following parts:（1） The synthesis and thermal properties and other related research of ladder-like polyvinylsilsesquioxanes （LPVS）. Ladder-like poly（vinylsilsesquioxanes）（LPVS） with substitutional vinyl which was side-by-side polymerized （LPVS-SP） and contains four parallel chains in the skeleton were synthesized by two steps: first, LPVS was prepared by stepwise coupling polymerization on the basis of amido H-bonding self-assembling template from vinyltrichlorosilane （VTCS）; then the vinyl of LPVS was polymerized side by BPO at high temperature. The composition and structure of the products have been characterized by ¹HNMR, ²⁹Si NMR, FTIR, TEM, SEM, XRD and elemental analysis, and then its formation mechanism is suggested. LPVS-SP possesses better thermal stabilities than LPVS for its four-parallel-chain structure and stable Si-0 bond. The thermal crosslinking and pyrolysis of LPVS-SP are studied by heating it in vacuum. X-ray diffraction measurements and weight measurements indicate that the turning point temperature from weight loss to inter-molecules thermal crosslinking is around 700°C. At last, LPVS is introduced to modify montmorillonite （MMT）: the intercalated LPVS-OMT nanocomposite was prepared by solution blending, and then it is further treated at 250.0°C for 2 hours in order to eliminate surfactant in OMT.. SAXS and TGA suggest that the nanocomposite retains its intercalated structure and exhibits better thermal stability, which implies potential application of this polymer composite.（2） Synthesis and characterization of Octa（tetramethylammonium） polyhedral oligomeric silsesquioxanes （TMN-POSS） and Poly（bromophenylsilsesquioxanes） （Br-POSS） and their polystyrene composites enhanced combustion properties. TMN-POSS was synthesized from tetraethoxysilane and （CH₃）₄NOH-5H₂O. It is used as fillers to prepare TMN-POSS/PS composites. When compared to pure PS, PS composites with loads of 20% and 30% of TMN-POSS in the composite can decrease the peak heat release rate（HRR） of composites by 31.7% and 54.6%, the average HRR by 17.6% and 41.5%, the peak CO release rate by 55.3% and 66.1%, the peak CO₂ release rate by 23.8% and 53.1%, the concentration of CO₂ by 31.1% and 62.0% respectively. The Limit Oxygen Index （LOI） also can be raised from 16.5 to 22 and 23 respectively.The Octaphenyl POSS （Ph-POSS） is synthesized via the hydrolysis and condensation of phenyltrichlorosilane （PhSiCl₃） and the subsequent rearrangement reaction catalyzed by tetramethylammonium hydroxide. Poly（bromooctaphenylsilsesquioxane） （Br-POSS） are easily synthesized from Ph-POSS via bromination with Br₂/Fe system. Br-POSS together with Sb₂O₃ are used as fillers to prepare （Br-POSS + Sb₂O₃） /PS composites. When （Br-POSS+Sb₂O₃） compositions are as high as 15% and 20%, the peak HRR of composites is decreased from more than 900kW/m² to less than 200kW/m² , and LOI can be raised from 16.5 to 29 and 30 respectively.Improvement of combustion properties of the POSS/polymer composites mainly depends on barrier effect generated from silicon-oxygen cages of POSS, elements or groups of effective flame retardance in organic substituents of POSS, and dispersion of POSS in polymer matrix. There are both similarities and differences between the fire retardant mechanisms of TMN-POSS/PS composites and （Br-POSS+ Sb₂O₃） /PS composites. They contain same silicon-oxygen cages, possess similar dispersions, but have different organic substituents.（3） Studies on POSS-surfactants lamellar hybrids. Two-dimensional multilayered complex of Octabenzenesulphonate Polyhedral Oligomeric Silsesquioxane（ObsPOSS） modified by alkyltrimethylammonium bromide (C_nH_2n+1N（CH₃）₃Br, CnTAB, where n denotes the carbon number in the alkyl chain) via ion-exchange reaction. Lamellar framework was obtained for the different compatibility between the organic part （ObsPOSS core made up of silicon oxide） and the inorganic part （side group of ObsPOSS and surfactant alkyl chain）, the lamellar structure with a layer space from 3 to 5 nm can be confirmed by XRD, TEM and SEM. Similar lamellar hybrids can be obtained from octa（y-chloroammoniumpropyl） polyhedral oligomeric silsesquioxanes （OCAP-POSS） dodecyl benzene sulfonic acid sodium salt (C₁₈H₂₉NaO₃S, DBSS). Further research shows that different POSS to surfactant ratios result in different arrangement of layers: when there exists excessive POSS, the layer is arranged in a "Alkyl-POSS-POSS-Alkyl" sequence; while on the contrary, the layer is in "Alkyl-POSS" sequence. For one kind of lamellar hybrids with a given POSS to surfactant ratio, the layer space of changs linearly as a function of the alkyl chain length of surfactants.The synthesized lamellar hybrid has been used as fillers to prepare PS composite with improved combustion properties. A lamellar hybrid content as low as 1% in the composite can cause about a 50.1% decrease of peak HRR, however, a higher content of this hybrid doesn’t seem to work.更多还原