通过熔体自由基反应调控聚丙烯体系的链结构和相结构

熔融反应加工是聚合物改性和制备聚合物纳米复合材料的重要途径之一.在此过程中,多数加成聚合物由于受到热、剪切或引发剂作用,通常可原位形成大分子自由基反应中间体.我们系统地研究了如何利用这类大分子自由基调控聚合物分子链的拓扑结构和聚合物纳米复合体系的相结构与界面.然而,某些聚合物大分子自由基,如聚丙烯(PP),受其分子链化学结构决定,在熔融反应条件下非常易于发生降解.研究发现,将可控自由基聚合中调控自由基反应活性的方法应用在熔融反应过程中可以显著抑制PP的降解,促进主反应的发生,在制备长链支化聚合物、调控聚合物纳米复合材料的相结构方面发挥了重要作用.本文介绍了本研究组近几年来通过熔体自由基反应调控PP体系的链结构和相结构的相关研究工作,如实现PP的长链支化,制备高熔体强度PP;在制备PP/C60 、PP/碳纳米管(CNTs)纳米复合材料过程中,利用熔体界面区域所发生的自由基反应,提高了纳米粒子与PP的界面相互作用,改善了纳米粒子在PP中的分散状态等.     

纳米无机粒子/聚合物复合材料界面结构的研究

纳米粒子具有许多特性,聚合物中加入纳米粒子可以制备得到性能更加优异的复合材料,其中纳米粒子和聚合物基体间的界面对决定纳米复合材料的性能起着重要作用.本文综述了近些年来表征纳米无机颗粒/聚合物复合材料中界面结构的研究手段,如红外光谱(FTIR)、热重(TGA)、电子显微镜、小角中子散射(SANS)及小角X射线散射(SAXS)等,及界面结构与复合材料力学性能和热稳定性关系的研究进展.同时也介绍了纳米粒子对复合材料的渗透、光催化、阻燃、介电及导电性能的影响.最后对这一领域的研究进行了展望.     

高性能石墨烯/聚合物纳米复合材料的研究进展——界面作用力的设计及其影响

石墨烯是一种二维材料,具有极其优异的电学、力学、热学等性能,制备方法简单且价格低廉,可以在高性能聚合物基复合材料中展现无穷魅力.石墨烯在聚合物中的分散状态,以及与基体间的界面作用是构筑高性能石墨烯/聚合物纳米复合材料的关键因素.本文综述了石墨烯/聚合物纳米复合材料的界面作用力,包括氢键、π-π堆栈、共价、配位作用和成核—结晶作用,并总结和评述了这些界面作用力的优缺点和适用范围.最后展望了多种协同作用在构筑强界面作用力的石墨烯/聚合物基纳米复合材料中的应用前景.     

漆酚钛聚合物/蒙脱土纳米复合材料的制备、结构与性能

用溶液插层聚合方法制备漆酚钛聚合物/蒙脱土纳米复合材料(PUTi/OMMT),并用XRD、TEM和TG等对其结构、性能进行测试与表征.XRD结果表明,通过溶液插层,PUTi分子链进入了OMMT片层间,从而使片层间距增大.TEM观察表明OMMT片层在PUTi聚合物中基本达到纳米级分散.与PUTi相比,PUTi/OMMT纳米复合材料具有更好的耐热性能和抗紫外光性能.     

聚乙二醇/功能化石墨烯层状纳米复合材料热稳定性的提高

通过溶液共混技术成功制备了一系列聚乙二醇功能化石墨烯(GO-PEG)填充的聚乙二醇4000(PEG4000)基纳米复合材料.利用红外(FT-IR)、X衍射(XRD)、扫描电镜(SEM)、热重(TG)及玻璃化转变温度(Tg)等表征手段详细研究了复合材料的结构和热性能.结果表明:GO-PEG可均匀分散在聚合物基体中,纳米复合材料呈层状结构;组分间的较强界面相互作用协同增强了纳米复合材料的热稳定性能.最终提出了层状纳米复合材料的形成过程及机理.     

聚合物接枝纳米颗粒及其相容性共混物流变学

聚合物接枝纳米颗粒(Polymer grafted nanoparticles,PGNPs)是一类重要的聚合物改性填料。由于表面聚合物链的存在,在一定条件下,PGNPs可以均匀地分散在聚合物基体中,形成"完全相容性"聚合物纳米复合材料。近年来,PGNPs填充聚合物体系的结构-性能关系研究已成为高分子学科的研究热点。本文主要概述了PGNPs的制备及其填充聚合物体系的结构-性能关系。从PGNPs的设计制备、PGNPs在聚合物基体中的分散行为、PGNPs纳米复合体系流变行为和纳米复合材料力学性能4个方面介绍了该领域已经取得的研究进展和现状,并展望该领域今后的发展前景和研究方向。     

聚合物基纳米复合材料结构设计与电磁屏蔽性能研究

聚合物纳米复合材料以其质量轻、易加工成型、耐化学腐蚀等优秀特性成为电磁屏蔽材料的研究热点.复合材料的导电性是影响电磁屏蔽性能的关键因素,而聚合物基体中导电网络结构则决定了材料内部的电子传输效率,从而在很大程度上决定材料导电性能.合理的结构设计可以解决纳米填料在基体中易团聚、难分散的问题,实现低渗滤阈值、高导电性能/电磁屏蔽与多功能化的统一.我们围绕聚合物纳米复合材料的关键科学问题展开研究,取得一些创新性研究成果:(1)通过填料/基体界面调控,实现复合材料连续导电网络的构筑,制备系列低渗滤阈值聚合物导电复合材料;(2)发展三维导电结构预先构筑新方法,制备出高效导电网络,实现电磁屏蔽复合材料结构功能一体化设计与制备;(3)提出构建多界面结构策略,实现聚合物电磁屏蔽复合材料的轻量化设计.本专论针对我们研究成果进行总结,并对高性能电磁屏蔽纳米复合材料的发展前景进行展望.     

聚合物存在下纳米银复合材料的制备与表征

以聚丙烯腈聚乙二醇嵌段共聚物PAN-b-PEG-b-PAN为稳定剂, 在超声辐照下成功地制备了分散性较好、尺寸均匀的纳米银颗粒. 用X射线衍射(XRD)、红外光谱(FTIR)、透射电镜(TEM)、紫外-可见吸收光谱(UV-Vis)和热分析(TGA)等对制备的纳米银复合材料进行了表征. 红外结果表明超声辐照并没有破坏聚合物的链结构. 聚合物的引入, 对纳米银颗粒起到了很好的分散保护作用. 用低浓度的硝酸银溶液, 得到粒径较小的纳米银颗粒; 随着硝酸银浓度增大, 纳米银颗粒粒径也增大. 而聚合物的浓度增大时, 所得银纳米颗粒粒径减小. 对银纳米颗粒的形成机理进行了讨论.     

纳米复合材料中界面动态特性的扫描静电显微技术研究

纳米复合材料中的微观界面结构和界面作用对材料的宏观介电性能, 如介电常数、介电损耗、击穿强度等有十分重要的影响. 本文发展了一种基于扫描静电显微探针技术的测量方法, 可以直接表征二氧化钛/环氧树脂纳米复合材料的微观界面结构及相应的动态介电响应行为. 实验中利用扫描探针的纳米尺度分辨能力, 探测到不同温度下环氧树脂纳米复合材料的局域动态介电响应变化过程, 从而获得纳米颗粒与高分子界面相互作用及极化相关的温度特性. 进一步通过对二氧化钛纳米颗粒进行表面修饰, 得到了两种不同特性的二氧化钛/环氧树脂界面, 验证了不同界面作用引起的复合材料界面区域与非界面区域高分子链介电损耗图像的反差.     

聚苯乙烯/蒙脱土纳米复合材料的制备及结构研究

以可与苯乙烯发生共聚的阳离子表面活性剂乙烯苄基二甲基十八烷基氯化铵(VOAC)为插层处理剂改性蒙脱土(VC18-MMT),有机蒙脱土在超声波强剪切作用以及乳化剂作用下预分散在乳化剂溶液中,然后引入苯乙烯单体进行原位乳液聚合制备聚苯乙烯/蒙脱土纳米复合材料.采用XRD和TEM对纳米复合材料的结构进行了表征.结果表明,绝大多数的蒙脱土被剥离成单个片层均匀的分散在聚合物基体中;动态力学分析表明,纳米复合材料的储能模量和玻璃化温度均有所增加,而动态损耗有所降低;接枝在蒙脱土片层上的聚合物通过与锂离子进行阳离子交换反应提取下来,采用GPC和NMR对接枝聚合物的结构进行了表征,结果表明,接枝聚合物是较基体分子量低且分布很宽的苯乙烯和乙烯苄基二甲基十八烷基氯化铵的共聚物,计算表明每一个共聚物分子链上平均含有大约25个乙烯苄基二甲基十八烷基氯化铵分子.     

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.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Synthesis and antioxidative/anti-inflammatory activity of novel fullerene–polyamine conjugates

(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C₆₀, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine.