天然微晶纤维素晶须补强天然橡胶的研究

采用硫酸酸解天然微晶纤维素(microcrystalline cellulose,简称MCC)制备纳米微晶纤维素晶须(cellulosewhisker,简称CW),加入天然橡胶胶乳共沉后混炼硫化.结果表明,CW对天然橡胶具有明显的补强作用,经间苯二酚(R)与六亚甲基四胺(H)改性后,NR/RH-CW复合材料的模量、断裂伸长率和撕裂强度都进一步改善.热空气(100℃,72 h)老化后,NR/RH-CW复合材料的力学性能明显优于纯NR,其拉伸强度由28.54 MPa下降至21.78 MPa,变化率缩小至23.7%;断裂伸长率由594%下降至493%,变化率缩小至17.0%,而纯NR的拉伸强度由22.0 MPa下降至2.4 MPa,变化率为89.1%;断裂伸长率由579%下降至168%,变化率为71.0%.扫描电镜分析表明,RH-CW与NR基体的界面相容性较CW改善.热重分析表明,CW的加入使NR的5%失重温度降低,但残重增加,微分曲线在520℃处出现了一个小峰,RH-CW的加入,使该峰变大,残重进一步增加.     

硅土/酚酞聚芳醚砜复合材料的制备及性能

使用γ-氨丙基三乙氧基硅烷对硅土进行功能化改性,将功能化的硅土掺入酚酞聚芳醚砜(PES-C)中制备复合材料,并对其热学性能、力学性能及阻隔性能进行表征分析。结果表明,γ-氨丙基三乙氧基硅烷使硅土片层的层间距变大,使硅土处于半剥离状态,且通过溶液共混将表面修饰的片层硅土掺杂于PES-C中更有利于PES-C分子链的插入。所制备的复合材料的T-5%、T-10%和T max分别提升了10.2、10和3.9℃。另外,复合材料的拉伸强度提升8.4 MPa,断裂伸长率提升2.4%,模量提升560.7 MPa。复合材料的氧气渗透系数(P O 2)降低77.4%。     

一种硅烷偶联剂的合成及其在白炭黑/天然橡胶复合材料中的应用

采用γ-缩水甘油醚氧丙基三甲氧基硅烷(A187)与对氨基二苯胺(PPDA)反应,制备得到一种具有防老化功能的硅烷偶联剂,并通过1H-NMR、IR和MS对其结构进行表征.之后,将不同用量的硅烷偶联剂用于原位改性白炭黑制备防老功能化白炭黑/天然橡胶(NR)复合材料,并与相应的炭黑/NR、未改性白炭黑/NR及双-(γ-三乙氧基硅基丙基)四硫化物(Si69)改性白炭黑/NR在加工性能、增强性能和防老化性能方面进行对比.硫化特性数据表明,防老偶联剂的添加使复合材料的黏度降低,最大转矩增加,正硫化时间缩短.动态黏弹性能显示,改性后白炭黑的分散性得到明显提高.复合材料的力学性能先随防老偶联剂用量的增加而提高,之后到达平台.当防老偶联剂的用量大于或等于白炭黑质量的10.8%时,复合材料的拉伸强度与炭黑/NR、Si69改性白炭黑/NR相当,远大于未改性白炭黑/NR的强度;而其撕裂强度都大于3种对比复合材料.经过100℃下不同天数的热氧老化后,添加防老偶联剂的复合材料表现出良好的性能保持率,优于添加防老剂4020的3种对比材料,表明防老偶联剂具有更好的防护效果.     

膨胀蛭石填充聚甲醛复合材料的制备与性能

采用经硅烷偶联剂和十六烷基三甲基溴化铵有机插层处理的膨胀蛭石微粉(EV)填充改性聚甲醛(POM),通过熔融共混制备POM/EV复合材料,并讨论了EV含量对复合材料的力学性能及热稳定性的影响.研究结果表明:当EV添加量为2%(w)时,复合材料的断裂伸长率为66.2%,较纯POM提高44.5%;弯曲强度和缺口冲击强度分别为77.7 MPa和6.15 kJ/m~2,分别较纯POM降低了7.9%和2.4%.此外,当EV的添加量为5%(w)时,复合材料的结晶点较纯POM提高了1.4℃;且随着EV添加量的增加,复合材料的热稳定性越好.     

累托石/聚丙烯插层纳米复合材料的制备与性能

采用熔融共混法制备了有机改性累托石 (OREC)粘土 均聚聚丙烯 (PP)纳米复合材料 ,以X 射线衍射分析 (XRD)及透射电子显微镜分析 (TEM)观察了复合材料的相貌结构 ,研究了复合材料的力学性能及热性能 .结果表明 ,OREC在添加份数较少时可与均聚聚丙烯熔融插层形成插层型聚丙烯纳米复合材料 ,该复合材料与纯PP相比 ,具有较高的拉伸强度、断裂伸长率及冲击强度 .在有机粘土添加 2 %时 ,复合材料的拉伸强度、断裂伸长率、冲击强度最高 ,与纯PP相比 ,2 %添加量的聚丙烯纳米复合材料拉伸强度提高 6 5 7% ,断裂伸长率提高 2 89 3% ,冲击强度提高 14 1% ,10 %失重率时对应的热分解温度提高 50K .     

尼龙6/SiO_2纳米复合材料的制备及其力学性能和热稳定性

以表面含有氨基的可反应性纳米SiO2(RNS-A)和表面含有烷基碳链的可分散性纳米SiO2(DNS-3)作为填料,利用原位聚合法制备了尼龙6/SiO2纳米复合材料(相应的复合材料分别简记为RPA和DP3);采用透射电子显微镜观察了复合材料中纳米SiO2的表面形貌,并利用热失重分析仪测定了复合材料的热稳定性,进而考察了纳米SiO2表面功能基团对尼龙6力学性能和热稳定性的影响.结果显示,纳米SiO2能够很好地分散在尼龙6基体中,并使尼龙6的热分解温度提高10℃左右.与此同时,RPA的最大拉伸强度和冲击强度较纯尼龙6的分别提高34.5%和12.5%,DP3的最大拉伸强度和冲击强度分别提高18.2%和45.7%.这表明两种纳米SiO2均可以有效地提高尼龙6的力学性能和热稳定性;可以推测,纳米SiO2的增强效应与其在尼龙6基体材料中的分散和界面作用有关.     

明胶中α组分含量对明胶/羟基磷灰石复合材料力学性能的影响

选用α组分含量分别为20.5%,41%和50%的A、B、C 3种明胶作为原料,采用同时加入法制备了明胶/羟基磷灰石(HAP)复合材料.通过对干态复合物膜拉伸性能的测试和对比,发现,明胶α组分含量的变化对复合材料的弹性模量影响较大,而对拉伸强度和断裂伸长率的影响则相对较小,但总的来说,三者均随α组分含量的增加而增大.其中,α组分含量最高的复合物C的拉伸强度为86.40 MPa,弹性模量为2682.35 MPa,断裂伸长率为8.65%.另外,对复合物C基本性质的表征结果表明,该材料具有类似于自然骨的组成和结构性质,因此有望成为一种具有优异力学性能的骨替代材料.     

狼尾草特性及狼尾草/PP复合材料性能研究

对狼尾草茎秆进行拉伸性能测试和长径比测量、并进行X射线衍射图谱、红外光谱和热重分析,分别以三种粒径(40目、60目、80目)狼尾草茎秆纤维为填充材料,以聚丙烯(PP)为基体材料,使用模压成型工艺制备三种不同粒径的狼尾草/PP复合材料。对制备的复合材料进行了接触角测量、吸水性能和力学性能测试,并用扫描电子显微镜(SEM)观察了复合材料拉伸断面微观结构。结果表明:狼尾草茎秆纤维素类型为I型,相对结晶度为44%;40目、60目和80目三种目数狼尾草/PP复合材料24h吸水厚度膨胀率分别为7.7%、4.2%和4.4%;其中40目狼尾草/PP复合材料有较好的结合界面和较好的力学性能,其拉伸强度、弯曲强度、弯曲模量和冲击强度分别为10.47MPa、15.98MPa、1.9GPa和3.7kJ/m~2。由此得知,40目狼尾草/PP复合材料力学性能最好,但吸水性较强;60目狼尾草/PP复合材料具有较好的力学性能和一定的抗吸水性,综合性能最佳。     

纳米纤维素晶须的表面改性及其在环氧树脂中的应用

以棉纤维素为原料,采用硫酸水解法制备了纳米纤维素晶须.以N,N-二甲基甲酰胺(DMF)为分散介质,二甲基氨基吡啶(DMAP)为催化剂,十二烯基琥珀酸酐为酯化剂对纳米纤维素晶须进行化学改性,得到了一系列取代程度不同的改性产物(记为DCNW).采用红外光谱(FTIR)、X射线衍射(XRD)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等手段对DCNW的结构和性能进行了分析和表征.选择表面取代度为0.3的改性产物作为复合材料的增强相.该改性产物能在丙酮中均匀分散和稳定悬浮,并且保持了改性前纳米纤维素晶须的棒状形态和高结晶度.将其分散于环氧单体中,通过浇铸法制备了纳米复合材料,考察了改性纳米纤维素晶须添加量对纳米复合材料拉伸性能、动态力学性能及耐湿热性的影响规律.结果表明,与空白环氧树脂相比,添加了改性纳米纤维素晶须的纳米复合材料的拉伸强度、杨氏模量和断裂伸长率都得到了提高.玻璃化转变温度、耐湿热性也得到了显著改善.其中,当改性纳米纤维素晶须的添加量为3.5%时,拉伸强度从纯环氧的39.85 MPa提高到72.33 MPa,增加了82%;杨氏模量增大了21%;断裂伸长率从纯环氧树脂的2.45%提高到7.29%,增加了198%;Tg值从纯环氧的103.4℃,提高到134.1℃;吸水率从1.9%下降到1.4%.     

碳酸钙/芝麻秸秆/不饱和树脂三元复合材料的力学性能和热稳定性

采用浇注成型工艺制备碳酸钙/芝麻秸秆/不饱和树脂三元复合材料,研究了碳酸钙粉、芝麻秸秆粉相对含量对复合材料力学性能及热稳定性的影响。结果表明,所有复合材料的拉伸强度和弯曲强度均低于不饱和聚酯树脂浇注体。随着碳酸钙粉用量的增多,复合材料的拉伸强度逐渐升高,而弯曲强度先下降后逐渐增大,含10%碳酸钙粉和5%芝麻秸秆粉的复合材料具有最大弯曲模量2 672.11 MPa。复合材料的热稳定性随着碳酸钙粉用量的增加而逐渐上升。复合材料的吸水率高于纯树脂浇注体,在相同的浸泡周期中,秸秆粉含量越高,复合材料的吸水率越高。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

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%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.