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星形聚硅氧烷的热稳定性研究和结构表征 总被引:3,自引:0,他引:3
含六苯基环三硅氮烷 (P3N)的聚硅氧烷的低温性能与普通聚硅氧烷相当 .35 0℃ ,封闭氮气中老化2 4h后 ,含P3N 聚硅氧烷的热失重比普通聚硅氧烷低 4~ 10倍 ,随聚合物含氮量增加 ,其失重呈下降趋势 ,最低失重为 1 1% .六苯基环三硅氮烷三锂盐 (P3NLi)引发环硅氧烷聚合得到的含P3N 聚硅氧烷的2 9Si NMR谱、IR谱和分子量 (GPC)与特性粘数的关系证明其具有星形结构 相似文献
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以六甲基二硅氮烷(MMN)、四甲基二乙烯基二硅氮烷(MMNVi)和四甲基二硅氮烷(MMNH) 3种不同结构的二硅氮烷为胺源,通过与氯硅烷和三氯化硼反应,制备出具有不同封端结构的聚硼硅氮烷.其中,以MMN、MMNVi为胺源可获得液态产物;以MMNH为胺源时,因合成过程中发生活性基团间的过度交联导致产物凝胶.采用核磁共振波谱仪、红外光谱仪对液态前驱体聚合物及其热解产物的结构进行了表征.研究结果表明:通过“一锅法”制备的液态聚硼硅氮烷主链具有较多的支化和环状结构,随着封端结构中乙烯基含量的增加,所得前驱体的固化温度降低,固化反应活化能降低.与以MMN为胺源和封端剂合成的聚硼硅氮烷相比,以MMNVi为胺源所得前驱体固化前后陶瓷产率分别提高了14.9%及8.1%.并且,通过改变胺源的种类和比例可以调节热解产物的元素组成,合成的液态前驱体聚合物热解所得SiBCN陶瓷结晶温度高于1700℃. 相似文献
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在二乙酰丙酮铂存在下, 以紫外光引发AB4型单体双(N,N-二烯丙基胺基)甲基硅烷发生硅氢加成反应, 制备了超支化聚碳硅氮烷. 聚合产物通过FTIR, 1H NMR, 13C NMR和29Si NMR谱和体积排除色谱/激光光散射联用技术进行表征. 与常规加热条件下Karstedt's催化剂催化的硅氢加成聚合相比, 光引发聚合的反应速度快. 波谱分析表明, 聚合过程中以α位硅氢加成反应为主. 光引发聚合制备的超支化聚碳硅氮烷支化度(DB)和平均支化数(ANB)分别为0.46和0.53, 与理论值相近. 其重均分子量为12500 g/mol, 分子量分布系数为2.1, Mark-Houwink方程指数α为0.44, 与热聚合制备的超支化聚碳硅氮烷的参数相近. 相似文献
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主链含环三硅氮烷的聚硅氧烷的合成——环硅氮阴离子引发环硅氧烷开环聚合 总被引:3,自引:2,他引:1
在极性溶剂中合成了六苯基环三硅氮烷锂盐(P3NLi) .在促进剂的作用下,此锂盐成功地引发了环硅氧烷的开环聚合.通过对聚合物的含氮量、1H NMR、29Si NMR 谱的测试,结果证明所得到的聚合物中含有六苯基环三硅氮烷,并研究了聚合物的分子量(GPC) 与特性粘数的关系. 相似文献
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硅氮烷添加剂的水解稳定性对硅橡胶热稳定性的影响 总被引:6,自引:0,他引:6
采用一种新的方法研究了硅氮烷水解反应的动力学规律 ,根据实验数据测出硅氮烷水解速率对硅氮烷的浓度符合一级动力学关系 .计算出了几种硅氮化合物与水蒸气反应的表观活化能 ,结果表明硅氮烷的结构与其水解反应的表观活化能有密切的关系 .硅原子或氮原子上带有较大空间位阻的基团后 ,其水解稳定性提高 .其中六苯基环三硅氮烷 4的水解表观活化能为 2 14kJ mol,而苯基硅氮聚合物 5的水解表观活化能更达到 2 91 3kJ mol.添加到硅橡胶中的硅氮化合物水解表观活化能越大 ,即水解稳定性越高 ,其改进硅橡胶热稳定性的效果越好 .将 4和 5添加到硅橡胶生胶中 ,35 0℃下老化 2 4h的热失重分别为 0 96 %和 0 6 % . 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields. 相似文献
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N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
The review contains a concise historical account and information on the most significant researches undertaken by the staff
at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry
of Heterocyclic Compounds.
Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008. 相似文献
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Regiospecific and direct imidation of the methyl C(sp3)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products. 相似文献
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《Tetrahedron》2014,70(21):3377-3384
The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative. 相似文献
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Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献