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1.
用红外二向色性法测定高聚物不同红外谱带二向色性是研究高分子取向的有效方法[1]. 前文[2]中我们报道了广角X射线衍射法和透射电镜法对剥离型聚苯乙烯(PS)/蒙脱土纳米复合材料中的剪切诱导有序结构的研究结果. 研究表明, 该有序结构的主要来源是分散在PS基体中的蒙脱土初级粒子沿平行于样品表面方向的平面取向及其内部片层结构的进一步有序化. 本文用红外二向色性法研究了该纳米复合材料中PS的苯环和烷基链的取向行为, 并在此基础上提出了可能的形成机理.  相似文献   

2.
聚合物/层状硅酸盐(PLS)纳米复合材料是近10余年来迅速发展起来的的交叉学科.由于其具有常规复合材料所没有的结构、形态以及较常规聚合物基复合材料更优异的性能等而引起人们的广泛关注[1].以往文献主要报道PLS纳米复合材料的制备与性能表征,如尼龙-6/蒙脱土[2]、PET/蒙脱土[3]和硅橡胶/蒙脱土[4]等.对于熔融加工过程中粘土片层及高分子的取向和结构研究很少.Kojima等[5]发现并研究了尼龙-6/蒙脱土纳米复合材料中的熔融剪切诱导取向结构,其X射线衍射与透射电镜(TEM)结果均表明,粘土片层沿熔体流动方向平行取向,但片层间距不等,因此为一平行取向但无序的结构.对于PLS纳米复合材料中的剪切诱导有序结构尚未见报道.  相似文献   

3.
李钟  李强 《化学学报》2003,61(3):422-426
从构筑静电自组装聚电解质/有机染料插层蒙脱土光致变色纳米复合膜所必需 的基本纳米构件--有机染料插层蒙脱土光致变色纳米复合物的设计出发,制备了具有光致 变色功能的蒙脱土/阳离子偶氮染料(GTL)均插层纳米复合物现,插人蒙脱土层 间的GTL热稳定性大幅度提高.由于GTL在纳米受限空间的超分子有序结构共轭,使 偶氮基发生了高达91 nm的显著红移.使用该插层纳米复合物构件与阳离子聚电解 质(PDAC)通过静电自组装得到了生长均匀、排列规整有序的光致变色聚电解质/ 阳离子偶氮染料插层蒙脱土纳米复合膜.  相似文献   

4.
悬浮缩聚法制备酚醛树脂/蒙脱土纳米复合材料   总被引:13,自引:0,他引:13  
采用悬浮缩聚方法在酸性催化剂作用下制备了酚醛树脂/蒙脱土纳米复合材料。以三种不同的蒙脱土:天然土、带有脂肪链季铵盐修饰蒙脱土和带有苯环基团的插层剂修饰的蒙脱土为原料制备了纳米复合材料,并考察了不同插层剂对纳米复合材料形貌的影响,发现带有苯环的插层剂修饰的蒙脱土与酚醛树脂的相容性能更好;研究了固化过程对纳米复合材料形貌的影响,XRD和TEM的结构表明固化过程可以促进带有脂肪链季铵盐修饰的蒙脱土进一步剥离,对其他两类的影响不大;此外还用TGA研究了纳米复合材料的热性能。  相似文献   

5.
用两种方法分别将四足配体铽配合物[TbL(NO3)]^2+和[TbL]^3+插层组装到了蒙脱土(MT)层板间,制备出超分子复合发光材料[TbL(NO3)^2+-MT和[TbL]^3+-MT。方法一:通过离子交换反应让配离子[TbL(NO3)]^2+取代钠+基蒙脱土(Na-MT)中的Na^+离子,插层组装到蒙脱土层板间。方法二:用配体L与铽基蒙脱土(Tb-MT)反应,使配体插入蒙脱土层板间与Tb^3+离子配位。用元素分析、XRD,FT-IR,UV-vis和热分析对材料进行了表征,并对其荧光性质进行了研究。结果表明,复合材料保持了蒙脱土良好的层柱结构特征,其层间距d001值与插层配离予的直径吻合较好,配离子以单层形式分布于蒙脱土层板间,复合材料中配合物的热稳定性有明显提高。在紫外光激发下,复合材料发出较强的Tb^3+特征荧光,其发射光谱与相应配合物的发射光谱很相似;复合材料中配合物的相对荧光强度较相应纯配合物有明显提高。荧光寿命较长;配合物的激发波长向可见光区发生位移,说明插层组装实现了对配合物激发波长的调制作用。  相似文献   

6.
PU/MOMMT纳米复合材料的制备与研究   总被引:3,自引:0,他引:3  
纳米复合材料由于其纳米尺寸效应,表面效应以及纳米粒子与基体界面间强的相互作用,具有优于相同组分常规复合材料的力学、热学等性能,引起了人们的广泛关注。用纳米材料改性聚合物,制备纳米复合材料是获得高性能高分子复合材料的重要方法。1998年以来,Pinnavaia等首先制备了聚氨酯,蒙脱土(PU/MMT)纳米复合材料,研究了有机蒙脱土在聚醚中的分散性。其后Chen等将聚羟基己内酯/蒙脱土(PCL/MMT)纳米复合材料加入到PCL和二苯基甲烷-4,4'-二异氰酸酯(MDI)合成的预聚体与1,4-丁二醇扩链反应后的溶液中,制备了PU/MMT纳米复合材料。少量PCL/MMT的引入可使复合材料的综合性能大幅提高。  相似文献   

7.
用FTIR和WAXD法研究了甲苯-2,4-二异氰酸酯(TDI)的邻位和对位异氰酸酯基团与蒙脱土表面羟基的修饰反应,在此基础上提出了结构模型;用TDI修饰后的蒙脱土成功制备了插层型聚苯乙烯/蒙脱土纳米复合材料,并用WAXD和TEM进行了表征.实验结果表明,修饰后TDI与蒙脱土表面形成化学键,使蒙脱土的片层间距显著增大,十六烷基三甲基溴化铵(CTAB)在蒙脱土层间由双层平行排列转变为双层脂肪链倾斜方式排列.在苯乙烯插层聚合过程中,蒙脱土层间距进一步扩大,其初级粒子在聚苯乙烯基体中的厚度约20~50nm.  相似文献   

8.
尼龙6/蒙脱土纳米复合材料的结晶行为   总被引:67,自引:4,他引:63  
用广角X 射线衍射(WAXD)、差示扫描量热仪(DSC)、小角激光散射(SALS)等手段研究了尼龙6/蒙脱土纳米复合材料的结晶行为.结果表明分散在尼龙6基体中的蒙脱土纳米粒子起成核剂的作用.蒙脱土的表面改性增加了蒙脱土和尼龙6分子之间的界面粘接,它具有阻碍尼龙6结晶的作用,使结晶活化能增加  相似文献   

9.
用FTIR和WAXD法研究了甲苯-2,4-二异氰酸酯(TDI)的邻位和对位异氰酸酯基因与蒙脱土表面羟基的修饰反应,在此基础上提出了结构模型;用TDI修饰后的蒙脱土成功制备了插层型聚苯乙烯/蒙脱土纳米复合材料,并用WAXD和TEM进行了表征。实验结果表明,修饰后TDI与蒙脱土表面形成化学键,使蒙脱土的片层间距显著增大,十六烷基三甲基溴化铵(CTAB)在蒙脱土层间由双层平行排列转变为双层脂肪链倾斜方式  相似文献   

10.
尼龙6/蒙脱土纳米复合材料的等温结晶动力学研究   总被引:29,自引:0,他引:29  
用DSC法研究了熔体插层制备的尼龙6/蒙脱土纳米复合材料的等温结晶行为.结果表明,加入少量的蒙脱土可明显提高尼龙6的结晶速率,降低球晶径向生长的单位面积表面自由能.从Avrami方程和Hofman理论出发,得出蒙脱土纳米粒子的存在可明显改变尼龙6的结晶行为  相似文献   

11.
Exfoliated polystyrene (PS)/laponite nanocomposites were prepared successfully. The characteristic doo1 diffraction peak of organo-laponite disappeared in the XRD patterns of nanocomposites, indicating that the laponite layers were exfoliated and the ordered crystal structure of laponite was destroyed because of the styrene polymerization. TEM observations showed that the exfoliated laponite primary particles were dispersed randomly in the PS matrix with lateral dimensions from 1 nm to 10 rim. SEM results showed that the PS/laponite nanocomposite particles were almost monodispersed spheres with the size of about 120 rim. Because of the interaction between PS and laponite nanolayers, the nanocomposites exhibited higher thermal stability and glass transition temperature when compared to pure PS.  相似文献   

12.
在恒定剪切速率下,利用旋转流变仪研究端羧基聚丁二烯/蒙脱土纳米复合凝胶的流变行为,同时利用X-射线衍射(XRD)和透射电镜(TEM)等表征手段研究其微观结构.研究结果表明,该体系在26~116℃的升-降温过程中,观察到不可逆转变和可逆转变两种流变行为,其中不可逆转变流变行为归因于蒙脱土片层的剥离过程,而可逆转变流变行为...  相似文献   

13.
Three polystyrene (PS)/clay hybrid systems have been prepared via in situ polymerization of styrene in the presence of unmodified sodium montmorillonite (Na‐MMT) clay, MMT modified with zwitterionic cationic surfactant octadecyldimethyl betaine (C18DMB) and MMT modified with polymerizable cationic surfactant vinylbenzyldimethyldodecylammonium chloride (VDAC). X‐ray diffraction and TEM were used to probe mineral layer organization and to expose the morphology of these systems. The PS/Na‐MMT composite was found to exhibit a conventional composite structure consisting of unintercalated micro and nanoclay particles homogeneously dispersed in the PS matrix. The PS/C18DMB‐MMT system exhibited an intercalated layered silicate nanocomposite structure consisting of intercalated tactoids dispersed in the PS matrix. Finally, the PS/VDAC‐MMT system exhibited features of both intercalated and exfoliated nanocomposites. Systematic statistical analysis of aggregate orientation, characteristic width, length, aspect ratio, and number of layers using multiple TEM micrographs enabled the development of representative morphological models for each of the nanocomposite structures. Oxygen barrier properties of all three PS/clay hybrid systems were measured as a function of mineral composition and analyzed in terms of traditional Nielsen and Cussler approaches. A modification of the Nielsen model has been proposed, which considers the effect of layer aggregation (layer stacking) on gas barrier. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1733–1753, 2007  相似文献   

14.
通过正离子交换将引发剂AIBA负载在蒙脱土上制得负载型引发剂V50-MMT.进而采用原位乳液聚合方法引发苯乙烯聚合制备PS/MMT纳米复合材料.采用XRD、TGA、DSC、TEM和抽提等方法对负载型引发剂和纳米复合材料进行了表征.结果表明,负载过程中引发剂AIBA进入了MMT的片层之间;聚合过程中介于片层间的引发剂因发生分解一方面产生自由基引发St聚合,另一方面MMT发生了剥离分散;由此法制备的PS/MMT纳米复合材料,MMT片层无规、均匀地分散于PS基体中,片层厚度在几个纳米至十几个纳米之间,长度为几十至几百个纳米不等;大量的PS链段以化学键接枝在MMT的片层上,接枝在MMT片层上的PS的分子量及其分布与游离的PS不同.  相似文献   

15.
The soap-free emulsion polymerization has been applied for preparing the surfactant-free polystyrene/layered double hydroxide exfoliated nanocomposite. The XRD and TEM determinations have been used to monitor the changes of interlayer spacing and morphology during polymerization. The results show that the obtained nanocomposite has the homogeneous structure of polymeric and inorganic components. Due to the absence of organic surfactant, the PS/LDH nanocomposite shows a remarked improvement on the onset decomposition temperature compared with virgin PS.  相似文献   

16.
The equilibrium structure and shear response of model polymer-clay nanocomposite gels are measured using X-ray scattering, light scattering, optical microscopy, and rheometry. The suspensions form physical gels via the "bridging" of neighboring colloidal clay platelets by the polymer, with reversible adsorption of polymer segments onto the clay surface providing a short-range attractive force. As the flow disrupts this transient network, coupling between composition and stress leads to the formation of a macroscopic domain pattern, while the clay platelets orient with their surface normal parallel to the direction of vorticity. We discuss the shear-induced structure, steady-shear rheology, and oscillatory-shear response of these dynamic networks, and we offer a physical explanation for the mesoscale shear response. In contrast to flow-induced "banding" transitions, no stress plateau is observed in the region where macroscopic phase separation occurs. The observed platelet orientation is different from that reported for polymer-melt clay nanocomposites, which we attribute to effects associated with macroscopic phase separation under shear flow.  相似文献   

17.
A simple approach to the synthesis of clay-silica nanocomposites is presented. Silica nanorings on the edges of clay sheets were synthesized by using a modified St?ber method. Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and fluorescence spectroscopy were employed to characterize the prepared nanocomposites. TEM results show that the average size of the nanorings increases with the growth of silica. XRD results indicate that the layered structures of clay can be found in the nanocomposite and the growth of silica nanorings expands the d spacing of clay platelets. The mechanism of the formation of the nanorings is discussed. The preparation of polystyrene (PS) brushes on the surfaces of silica nanorings by atom-transfer radical polymerization is also reported. The polymer nanocomposite with negatively charged clay surfaces and hydrophobic polymer brushes on the silica nanorings can be used in Pickering emulsions, and PS colloidal particles with clay-silica on the surfaces were prepared.  相似文献   

18.
A novel nanocomposite with a core-shell structure containing polystyrene (PS), polyaniline (PANI), and Au nanoparticles (NPs) was synthesized. The nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). Cyclic voltammetric experiments indicated that the nanocomposite had excellent redox ability in a wide range of pH values. The existence of Au NPs resulted in a higher electrical conductivity of the nanocomposite. As a model, glucose oxidase (GOD) was entrapped onto the nanocomposite-modified glassy carbon electrode (GCE) and applied to construct a sensor. The immobilized GOD showed a pair of well-defined redox peaks and high catalytic activity for the oxidation of glucose.  相似文献   

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