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Chi Thanh Nguyen Dong Pyo Kim Suk Bong Hong 《Journal of polymer science. Part A, Polymer chemistry》2008,46(2):725-732
A polycarbosilane (PCS) with a higher number–average molecular weight (2710 vs. 1570), and hence with a higher ceramic yield (74 vs. 68%), compared to a commercial Nipusi type S PCS has been synthesized via the catalytic decomposition of polydimethylsilane at 400 °C using H‐ITQ‐2, a delaminated zeolite with a very high external surface area, as a solid acid. The silicon carbide film fabricated using this PCS was found to show a much lower level (16 vs. 39%) of shrinkage than the commercial PCS‐derived film, together with better mechanical properties, suggesting the potential of its preceramic polymer to produce robust ceramic coatings. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 725–732, 2008 相似文献
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为了研究合成温度对聚铝碳硅烷(PACS)结构的影响, 采用具有Si—C骨架结构的低分子量液态聚碳硅烷(LPCS)与乙酰丙酮铝[Al(AcAc)3]为原料, 在300, 360和420 ℃下分别合成了固态PACS, 并对合成的PACS样品进行元素组成及结构表征. 表征结果显示, 合成温度明显影响样品的Al, O含量及Si—H键数量. 合成温度升高, Al含量与O含量增大, 但PACS中的Si—H键数量急剧减少, 在360 ℃下合成的样品具有理论Al含量, 而在300和420 ℃下合成的样品的Al含量分别小于和大于理论Al含量. 27Al MAS NMR结果显示, Al与O形成AlO4, AlO5和AlO6 三种配位形式. 反应过程中消耗Si—H键形成Si—O—Al交联结构是PACS数均分子量及多分散系数增加的主要原因. 相似文献
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聚碳硅烷/纳米镍粉的热裂解 总被引:3,自引:0,他引:3
聚碳硅烷/纳米镍粉的热裂解王军*宋永才冯春祥(国防科学技术大学材料工程与应用化学系长沙410073)关键词聚碳硅烷,纳米材料,镍,热解,碳化硅纤维1996-09-17收稿,1996-12-13修回国家攻关计划和“863”高技术资助项目聚碳硅烷(PCS... 相似文献
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Israel Cabasso Youxin Yuan Xinwei Wang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(23):7677-7689
An electropolymerization of haloalkylhalosilanes (Cl? R? SiCH3Cl2) that possess two types of electroactive sites, that is, the C? Cl and Si? Cl bond is described. The one‐pot synthesis method is shown to yield branched polycarbosilanes having a regular carbon block‐spaced silicon backbone structure. A series of branched polycarbosilanes, [? R? SiCH3? ]n with R being ? CH2? , ? C2H4? , ? C3H6? , and ? CH2? C6H4? C2H4? , have been successfully electropolymerized with Mn up to 42,600 Dalton. Experimental and simulation cyclic voltammetry of these monomers and the computational examination of their LUMOs are applied to study the electropolymerization mechanism. The results suggest that polymerization proceeds by iterating steps involving (1) electroreduction of a C? Cl bond to a carbanion, which is catalyzed by silylanion radical [Cl SiCl(CH3)RCl] and/or Ni(0)/TDA‐1; and (2) nucleophilic attack of carbanions to Si? Cl bonds of a second monomer or oligomer to extend the polymer chain. The investigation reveals that the R spacer has a considerable impact on the polymerizability of the corresponding monomer. Such interfacial polymerization resembles a template polymerization, leading to unique microstructures that were preserved even after converted to silicon carbide ceramics at high temperatures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7677–7689, 2008 相似文献
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Yangpeng Duan Gaoming Mo Haijun Chen Yanqin Liang Zhenduo Cui Xianjin Yang Shengli Zhu Zhaoyang Li Liu He Qing Huang Zhengren Huang 《应用有机金属化学》2019,33(2)
The synthesis of polyaluminocarbosilane (PACS) using liquid polysilacarbosilane (PSCS) and aluminum acetylacetonate [Al (acac)3] by a high‐pressure method is reported for the first time. The effects of reaction time, temperature and feed ratio on the structure of PACS are investigated in detail by gel permeation chromatography, Fourier transform‐infrared, 1H‐NMR, 29Si‐NMR and 27Al‐NMR methods. It was found that the molecular weight and its polydispersity, as well as the branching degree of the molecular structure of PACS, increase with reaction time and temperature. Increasing the weight percentage of Al (acac)3 has a similar effect as temperature. Combined with the gas chromatography–mass spectroscopy results, the reaction mechanism is proposed, which contains three main reactions: (i) cleavage and rearrangement reaction of PSCS; (ii) silicon‐free radicals react with Al (acac)3, leading to cleavage of O=C and/or O‐C bonds and formation of AlOx ligands; and (iii) conversion reaction of Al ligands from AlO6 into AlO5 and AlO4. It is also found that PACS prepared by high‐pressure method has a lower branched molecular structure in comparison to its analog prepared under ambient pressure conditions, and it is achieved to increase the molecular weight and ceramic yield of PACS, which is beneficial for the processing and overall quality of the final product. 相似文献
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Cassandre Piriou Lucas Viers Romain Lucas Fabien Bouzat Hatim Laadoua Yves Champavier Sylvie Foucaud Cristina Coelho Florence Babonneau 《应用有机金属化学》2018,32(9)
A hyperbranched polymer, a precursor of silicon carbide (SiC), was successfully synthesized using a hydrosilylation reaction with Karstedt's catalyst. This reaction was optimized with the use of a rheometer coupled with an infrared spectrometer. The polymeric precursor was characterized using NMR and Fourier transform infrared spectroscopies, and dynamic rheology. The polymerization reaction was followed in situ by combined rheological and infrared measurements, indicating a gel‐like behaviour for alkene conversions higher than 0.55. Overall second‐order kinetics was determined for the hydrosilylation reaction. Pyrolysis at 1400 °C led to porous materials with β‐SiC and free carbon. 相似文献
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基于液态聚碳硅烷的聚铝碳硅烷的合成与表征 总被引:1,自引:0,他引:1
采用液态聚碳硅烷与乙酰丙酮铝在常压下反应合成了具有不同铝含量的聚铝碳硅烷(PACS),由于不需要循环回流过程,因此该方法简单方便,安全性高.在与合成聚铝碳硅烷相同的条件下,对单纯的液态聚碳硅烷原料进行保温处理,所得产物的分析表征结果显示,该原料在反应条件下基本保持稳定,不会自聚或者裂解.不同铝含量的聚铝碳硅烷的元素分析结果表明,随着乙酰丙酮铝加入量的增加,聚铝碳硅烷中的铝含量增加,同时氧含量增加,氢含量减少,且乙酰丙酮铝中的铝元素几乎全部引入到液态聚碳硅烷中.GPC分析结果显示,随着铝含量的增大,PACS的数均分子量增大,分子量分布变宽.红外光谱和核磁共振波谱分析结果表明,液态聚碳硅烷与乙酰丙酮铝的反应主要以消耗Sj-H键的方式进行,铝元素以AlO_4,AlO_5和AlO_6 3种配位形式存在,同时形成Si-O-Al交联键,使得聚铝碳硅烷的分子量增大,分子量分布变宽. 相似文献
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Polycarbosilane (PCS) was synthesized by the polycondensation of trichloromethylsilane and trimethoxyvinylsilane in the presence of sodium metal. PCS has a highly crosslinked structure, high ceramic yield and high surface area. Titanium metal ion was attached to the polycarbosilane and its catalytic activity was investigated. The Knoevenagel condensation reaction catalysed by titanium‐incorporated polycarbosilane is reported. The titanium‐incorporated PCS catalysed the reaction well and with a diverse set of substrates the reaction proceeded with good yield. PCS‐supported transition metal catalysts have been prepared for the first time and used successfully in the Knoevenagel condensation reaction. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Takuya Ogawa Masashi Murakami 《Journal of polymer science. Part A, Polymer chemistry》2003,41(2):257-263
Soft–hard binary polymer blends consisting of amorphous poly(silylene methylene)s (PSMs) and crystalline poly(diphenylsilylenemethylene) were prepared by both melt processing at 360 °C and in situ polymerization at 300 °C. Linear and siloxane‐crosslinked PSMs were used as amorphous components for the purpose of determining how the crosslinks affected the interactions between the component polymers. Differential scanning calorimetry and dynamic mechanical analysis indirectly suggested that discernable differences between the blends containing linear and crosslinked PSMs were attributable to the degree of interactions between the amorphous and crystalline components. The morphological differences between these blends were studied with transmission electron microscopy. The dispersion phase was smaller in the blends containing crosslinked PSM than that in the blends containing linear PSM. This directly indicated that a larger interaction between the amorphous and crystalline phases was obtained by the introduction of crosslinks because of the smaller viscosity difference between the phases and a larger degree of polymer chain entanglement. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 257–263, 2003 相似文献