原位聚合法制备聚合物/纳米SiO_2复合材料的研究进展

纳米SiO_2改性聚合物制备的关键在于提高纳米粒子与聚合物基体的相容性及分散性;对纳米SiO_2进行不同的表面改性及选择合适的复合材料制备方法可以改变纳米粒子与聚合物基体的界面结合方式以及相容性和分散性,进而在不同程度上影响材料的性能.本文介绍了改性前后纳米SiO_2与聚合物基体的多种界面结合方式,对近年来利用原位聚合法制备聚合物/纳米SiO_2复合材料的研究现状和进展进行了综述.     

聚合物-纳米金在油水界面的自组装及有序结构的构筑

聚合物-纳米金复合物既具有金纳米粒子的光、电及催化性能,又具有聚合物的可加工性及对外界的刺激响应性,因此已成为高分子科学及材料科学研究的热点。本文主要介绍了我们实验室在聚合物-纳米金在油水界面的自组装及有序结构的构筑研究方面的相关工作:(1)利用界面聚合的方法制备侧链接枝亲水性金纳米粒子的聚苯乙烯及杂化聚合物在水溶液中的自组装;(2)亲水性金纳米粒子及疏水性聚合物(或疏水性磁性纳米粒子)在油水界面的自组装研究;(3)利用金纳米粒子为交联点制备具有温度响应性聚合物微凝胶的研究。     

计算机模拟研究聚合物纳米复合材料的分散与界面

针对聚合物纳米复合材料,系统综述了计算机模拟技术(分子动力学模拟)在纳米颗粒的分散与聚合物-纳米颗粒界面作用取得的成果与进展,包括不同形状纳米颗粒在聚合物基体的分散机理、相行为与微观结构、纳米颗粒对分子链构象的影响(分子链均方回转半径的变化)、分子链在纳米颗粒表面结构(取向与排列)、分子链与纳米颗粒界面作用能、界面区分子链活动性与纳米颗粒形成的网络结构.为构建聚合物纳米复合材料的组成、结构与性能之间的关系,提出了3个模拟方面的挑战,包括发展长时间跨尺度计算机模拟技术、建立准确模拟材料力学性能的方法与导电导热功能性的模拟.     

层离型PMMA/镁铁双氢氧化物纳米复合材料的热降解研究

通过原位聚合方法制备了以非水溶性聚合物(聚甲基丙烯酸甲酯,PMMA)为基体,与MgFe双氢氧化物(LDH)具有良好相容性的层离型纳米复合材料.采用小角、广角X射线衍射(XRD)及透射电镜(TEM)对纳米复合材料的微观结构进行了分析,通过热重分析(TG)和玻璃化转变研究了纳米复合材料在空气和氮气氛围下的热降解过程.实验结果表明,MgFe-LDH的引入显著提高了聚合物基体的热降解温度和玻璃化转变温度,纳米复合材料的热稳定性显著提高.其中含量1.6 wt%的层离型纳米复合材料在失重50%时的热降解温度比纯样提高约69℃.并且整个纳米复合体系的相容性良好,含量8.0 wt%的样品,其可见光透过率仍可达90%以上.     

Papain/HA-Phe自组装复合纳米粒子及乳化性能

用L-苯丙氨酸乙酯(L-Phe)改性透明质酸(HA)双亲性生物大分子(HA-Phe)负载生物活性分子木瓜蛋白酶(papain),HA-Phe和Papain通过静电、氢键和疏水相互作用自组装形成生物基Papain/HA-Phe复合纳米粒子.用动态光散射(DLS)和透射电镜(TEM)对复合纳米粒子的尺寸和形貌进行表征.结果显示,形成的复合纳米粒子为球形结构,粒径约308 nm.以此复合纳米粒子为颗粒乳化剂稳定白油,形成水包油型Pickering乳液.乳液的扫描电镜(SEM)显示,复合纳米粒子吸附在油水界面,形成复合纳米粒子的吸附层以稳定乳液.详细研究了pH和盐浓度对复合纳米粒子性质和复合纳米粒子乳化性能的影响.结果表明,随着pH增加,复合纳米粒子在油滴表面的吸附数目减少,乳化性能降低;随着盐浓度增加,复合纳米粒子的形变能力增强,乳化性能提高.进一步研究了乳液中木瓜蛋白酶的活性及美白效果.研究表明,制备的乳液保留了一定的活性,且具有一定的美白效果.     

不同形貌镍纳米粒子-石墨烯复合材料的制备及微波吸收性能

采用原位化学还原方法制备出了两种不同形貌的镍纳米粒子-石墨烯(Ni-GNs)复合材料, 并研究了形貌对复合材料电磁吸收性能的影响. 制备过程中通过改变反应物的加入顺序, 制备出球形和刺球形镍纳米粒子-石墨烯复合材料. 利用X射线衍射(XRD)仪、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和矢量网络分析仪(VNA)对复合材料的形貌、结构和微波吸收性能进行了表征. 结果表明: 刺球形镍纳米粒子-石墨烯复合材料相比于球形镍纳米粒子-石墨烯复合材料具有优异的电磁吸收性能, 其原因是由于复合材料中刺球形镍纳米粒子独特的各向同性天线形貌引起的尖端放电效应. 因此利用简单的原位化学还原制备不同形貌镍纳米粒子-石墨烯复合材料的方法可以作为其他复合材料制备的总体路线.     

聚合物/纳米碳酸钙复合材料的制备

提出了一种制备聚合物/碳酸钙复合材料的技术.即先将纳米碳酸钙粒子在温和条件下分散到水溶液中,再在较弱的外场作用下混合分散到聚合物熔体中,使用此方法制备的4种典型聚合物(聚乙烯、聚丙烯、聚碳酸酯和聚脂)的纳米复合材料,通过扫描电镜观察纳米粒子以纳米尺寸均匀分布于树脂基体中.聚碳酸酯复合材料的相对分子质量变化不大,而且复合材料的某些力学性能有所提高,证明此种方法可用于极性与非极性聚合物制备纳米复合材料.     

聚吡咯及其复合热电材料研究进展

聚吡咯(PPy)以其环境稳定性好、低毒、可调的导电性等优点,在热电材料研究方面日益受到人们的关注。采用纳米结构导电聚合物或将有机导电聚合物材料与高导电性的碳纳米粒子进行复合制备聚合物/碳纳米粒子复合材料,可以有效地改善其热电性能。本文结合该领域近年来的研究进展,重点讨论了PPy及其复合热电材料的研究结果,对一维纳米结构PPy的制备也进行了论述。     

粒子-聚合物相互作用与粒子-粒子相互作用对聚合物基纳米复合物力学性能的影响

聚合物基纳米复合物(PNCs)具有比传统高分子材料更加优异的光学、力学、热力学等性能,广泛应用于各个工程领域.而纳米粒子(NPs)对材料性能提高的机理则是当前聚合物纳米复合物领域研究的重要问题,聚合物纳米复合体系相互作用的影响因素众多,至今尚未明确并完整建立复合体系相互作用与性能增强之间的关系.本文总结了近年来关于纳米粒子填充聚合物基体力学性能的研究,从粒子-聚合物相互作用和粒子-粒子相互作用角度阐述了聚合物纳米复合体系力学性能的增强机理,并根据体系中不同的结构关系分别总结了聚合物/未改性纳米粒子复合体系和聚合物/聚合物接枝纳米粒子复合体系中影响力学性能的因素.该部分内容具有重要的理论和实践意义,有助于构建复合体系微观结构与宏观性能之间的关系,进而对微观层面调控PNCs的力学性能提供指导.     

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.     

Interfacial Improvement of Carbon Fiber/Epoxy Composites by Incorporating Superior and Versatile Multiscale Gradient Modulus Intermediate Layer with Rigid-flexible Hierarchical Structure

In order to enhance the interfacial adhesion of carbon fiber(CF) and polymer matrix, a multiscale gradient modulus intermediate layer with rigid-flexible(GO-PA) hierarchical structure was designed and fabricated between CFs and matrix by a facile and businesslike strategy. The polarity, roughness and wettability of CFs surface as well as the thickness of intermediate layer in composite have been significantly increased after rigid-flexible hierarchical structure was constructed. The IFSS, ILSS, compression and impact toughness manifested that the hierarchical structure could bring about a fantastic improvement(76.8%, 46.4%, 40.7% and 37.8%) for the interfacial and mechanical properties than other previous reports. Consequently, the establishment of CF surface with gradient modulus rigid-flexible hierarchical structure via regulation of nanoparticles and polymer array would open a new, viable and promising route to obtaining high-performance composites.     

Preparation of Isotactic Polypropylene/Organoclay Nanocomposites by Solution Mixing Methodology: Structure and Properties Relationships

Isotactic Polypropylene (iPP) based nanocomposites filled with organo-clay nanoparticles were prepared and the relationships between their structure and properties were investigated. Modified C₁₆-C₁₈ smectite clay nanoparticles were used in order to promote matrix/filler compatibilization and to improve interfacial adhesion. X-Ray analysis performed on the nanocomposites demonstrated that at low organo-clay content (1 and 3% by weight) a nanostructure has been obtained, while in presence of 5% by weight of organoclay cluster regions have been formed. Mechanical tests showed that the elastic modulus increases of about 20% compared to the neat polymeric matrix value when 1 and 3% of nanofiller is added.     

PERFORMANCE IMPROVEMENT OF POLYMERS BY THE ADDITION OF GRAFTED NANO-INORGANIC PARTICLES

An irradiation grafting method was applied for the modification of nanoparticles so that the latter can be added topolymeric materials for improving their mechanical performance using existing compounding techniques. The followingitems are discussed in this paper: (a) chemical interaction between the grafting monomers and the nanoparticles duringirradiation, (b) properties including modulus, yield strength, impact strength and fracture toughness of the resultantcomposites, and (c) possible morphological changes induced by the addition of nanoparticles. Though irradiation graftingpolymerization, nanoparticle agglomerates turn into a nano-composite microstructure (comprised of the nanoparticles and thegrafted, homopolymerized secondary polymer), which in turn builds up a strong interfacial interaction with the surrounding,primary polymeric matrix during the subsequent mixing procedure. Due to the fact that different grafting polymers broughtabout different nanoparticle/matrix interfacial features, microstructures and properties of the ultimate composites could thusbe tailored. It was found that the reinforcing and toughening effects of the nanoparticles on the polymer matrix can be fullybrought into play at a rather low filler loading in comparison to conventional particulate filled composites.     

Efficient thermal properties enhancement to hyperbranched aromatic polyamide grafted aluminum nitride in epoxy composites

Aluminum nitride (AlN) nanoparticles were firstly treated with a silane coupling agent, γ‐aminopropyl‐triethoxysilane (γ‐APS), to introduce amine groups (AlN‐APS), then grafting of the hyperbranched aromatic polyamide started from the modified surface (AlN‐HBP). The surface modified AlN nanoparticles were characterized by Fourier transform infrared, nuclear magnetic resonance, and thermogravimetric analyzer. Then the nanoparticles with these three different interface structures were selected as reinforcing fillers for epoxy composites. The study reports the influence of interfacial structure of nanoparticles on the morphology and thermal properties of epoxy composites. It was found that the AlN‐HBP nanoparticles result in a strong interface and thus the incorporation of the AlN‐HBP nanoparticles not only improved the dispersion of the nanoparticles in the epoxy matrix but also enhanced the thermal conductivity, thermal stability, glass transition temperatures, and dynamical thermomechanical properties. Copyright © 2013 John Wiley & Sons, Ltd.     

Epoxy Nanocomposites

The formation and physical properties of epoxy nanocomposites with carbon (nanotubes, graphene, and graphite), metal-containing, and aluminosilicate (montmorillonite and halloysite) fillers are considered. The mutual effect of both a matrix and nanoparticles on the composite structure is discussed. The role of the interfacial layer in the mechanical properties of nanocomposites is revealed. It is found that the concentration dependence of electrical and thermal conductivities of the composites is related to the percolation phenomenon.     

Gold Nanoparticles Doped Three‐Dimensional Sol‐gel Matrix for Amperometric Human Chorionic Gonadotrophin Immunosensor

A novel electrochemical immunosensor for human chorionic gonadotrophin (hCG) was proposed by immobilization of hCG in gold nanoparticles doped three‐dimensional (3D) sol‐gel matrix and an interfacial competitive immunoreaction. The 3D organized composite structure was prepared by assemble of gold nanoparticles into a hydrolyzed (3‐mercaptopropyl)‐trimethoxysilane sol‐gel matrix, which showed good biocompatibility. After the interfacial competitive immunoreaction the formed HRP‐labeled immunoconjugate showed good enzymatic activity for the oxidation of o‐phenylenediamine by H₂O₂. With a competitive format, a method comprising of o‐phenylenediamine‐H₂O₂‐immobilized HRP labeled hCG immunoconjugate system for immunoassay of hCG from 5.0 to 30.0 mIU mL^?1 was developed. The immunosensor showed good precision, high sensitivity, acceptable stability and reproducibility and could be used for detection of hCG in human serum with the consistent results in comparison with those obtained by a commercial analyzer.     

Nanocavitation in silica filled styrene‐butadiene rubber regulated by varying silica‐rubber interfacial bonding

The influence of filler‐matrix interfacial bonding on the nanocavitation of rubber materials has not been explored clearly. We herein report the nanocavitation modes and geometrical features impacted by varying the silica‐styrene‐butadiene rubber interfacial bonding. The interfacial bonding is tuned by grafting different amount of multi‐functional silane coupling agents on to the silica nanoparticles. By using synchrotron radiation small angle X‐ray scattering measurements, 2 major classes of cavitation were detected. When the interfacial strength was weak, fibrillar nanocavitation, with lengths ranging from 120 to 217 nm and diameter of the same order of the particle size, was generated by interfacial decohesion at the particle pores along the stretching direction. After grafting modification, the fibril‐like nanocavitation almost disappears and nanocavitation content decreases first at lower grafting density; then nanocavitation content increases at higher grafting density, where nanocavitation in confined rubber regions dominates. It is finally proposed that nanoparticle interfacial strengthening can change the cavitation mode from interfacial decohesion to confined rubber matrix nanocavitation, which exhibits more favorable prevention of the macroscopic failure by cracking.     

Nanoparticle assembly at fluid interfaces: structure and dynamics

The self-assembly of nanoparticles at fluid interfaces, driven by the reduction in interfacial energy, was investigated. With spherical, tri-n-octyl-phosphine-oxide covered cadmium selenide (CdSe) nanoparticles (1-8 nm), thermal fluctuations compete with the interfacial segregation giving rise to a size-dependent self-assembly of the particles. The structure of the nanoparticle assembly was studied using electron microscopy, atomic force microscopy, and X-ray scattering in situ, which indicate that the particles form a densely packed monolayer. The energetics of the adsorption of nanoparticles onto the interface was revealed by time-dependent fluorescence studies on a mixture of two different sized nanoparticles at the interface. The dynamics of the nanoparticles at the fluid interface, probed using fluorescence photobleaching methods, suggests a liquid-like behavior. The results have implications in the design of hierarchical self-assemblies of nanoparticles for the one-step fabrication of devices on multiple length scales.     

Preparation and application of cross-linked core-shell PBA/PS and PBA/PMMA nanoparticles

This paper reports the preparation of cross-linked core-shell poly(butyl acrylate)/polystyrene (PBA/PS) and poly(butyl acrylate)/poly(methyl methacrylate) (PBA/PMMA) nanoparticles via seeded emulsion polymerization and their application in nylon-based composites. A highly cross-linked structure was formed in both the cores and the shells by using a cross-linking agent, which could prevent the migration of hydrophobic PS shells to the inside of particles. There were covalent bonds on the interfaces between the cores and the shells of both particles. The average particle sizes were 40–50 nm, and the size distributions were narrow. The kinetics of polymerization was investigated. Well-defined core-shell structure and narrow particle size distribution could be achieved under starved conditions of monomer feeding. Furthermore, PBA/PMMA particles were used to fill nylon 6, good dispersion was obtained because of the strong interfacial interaction between the nanoparticles and the nylon 6 matrix and the good deformation ability of nanoparticles, and the toughness and rigidity of the composites were improved evidently. __________ Translated from Acta Polymerica Sinica, 2005, (6) (in Chinese)