催化剂性质对碳纳米管可控生长的影响

碳纳米管独特的物理化学性质与其结构密切相关。目前,化学气相沉积法已成为低成本制备碳纳米管的常用方法,其中催化剂性质是实现碳纳米管可控生长的关键。催化剂作为碳纳米管成核生长的核心位点,对碳纳米管的结构起着决定性的作用。本文从适宜于化学气相沉积法生长碳纳米管的催化剂的结构与性质入手,综述了近几年催化剂在碳纳米管长度、管径、管壁数及手性控制等方面的研究进展。     

用带不同侧链的双取代聚乙炔衍生物增溶多壁碳纳米管

采用不同的双取代聚乙炔与多壁碳纳米管复合,通过π-π相互作用和聚合物链缠绕实现了对碳纳米管的增溶.这种方法对碳纳米管的结构没有损害,而且包覆到碳纳米管表面的双取代聚乙炔也显示了自身的荧光发射特性.     

PAn-PEG-PAn三嵌段共聚物的合成和表征

在合成α,ω-双(对氨基苯基)聚乙二醇(BAPPEG)的基础上, 用化学氧化共聚法制备了PAn-PEG-PAn三嵌段共聚物. 研究了共聚时苯胺(An)与BAPPEG摩尔比(r)对共聚物的化学组成、UV-Vis谱图、热稳定性和在水溶液中的自组装特性的影响. 结果表明：随着r的增加, 共聚物中PAn链段的含量增大；其UV-Vis谱图中对应PAn链段的吸收峰出现红移, 且红移的程度增加； 热稳定性提高. 三嵌段共聚物在水中表现出自组装特性： 随着r的增加, 先形成粒径约为90 nm的PAn链段/PEG链段球型核壳胶束, 然后形成长为400～800 nm, 直径约为30 nm的棒状结构, 和棒状结构聚集形成的网状结构, 最后又变成球型胶束.     

一维新型碳的同素异形体:碳链

碳链是一种完全一维的、具有电子轨道sp杂化结构的新型碳的同素异形体.正是由于碳链的独特的一维结构,使其拥有区别于富勒烯、石墨烯和碳纳米管的化学键,从而表现出更加优异的性能,如:理论预言碳链的机械强度是石墨烯的几倍;碳链的导热也类似于石墨烯和碳纳米管;碳链是具有直接带隙的半导体材料,且带隙的大小可以通过其长度来调控,其长...     

聚乙二醇单甲醚修饰多壁碳纳米管的研究

多壁碳纳米管(MWNT)经过酸化、酰氯化后与聚乙二醇单甲醚进行接枝反应,实现了碳纳米管的表面修饰。经修饰的MWNT在水中的分散性大大增加。通过FTIR、XPS、Raman、TEM、TGA等手段表征了接枝后产物的化学结构,证明聚乙二醇单甲醚是以共价键的形式接入MWNT表面上的。并利用TGA结果估算出聚乙二醇单甲醚在MWNT表面的接枝密度约为平均每256个碳原子上有一根聚合物链。     

高稳定性和水溶性的共轭聚电解质/单壁碳纳米管复合物的制备和表征

单壁碳纳米管（SWNTs）的分散性是影响其走向大规模应用的一个重要因素.尤其为满足未来绿色化学的要求,制备环保、稳定、均匀分散的单壁碳纳米管水溶液尤为重要.基于此,我们利用一种水溶性的共轭聚电解质聚（3-甲基咪唑盐己基噻吩）（P3MHT）,来分散单壁碳纳米管.通过紫外-可见光谱仪、荧光光谱仪、透射电子显微镜、纳米粒度-Zeta电位分析仪、热重分析仪等仪器对制备的聚噻吩/碳纳米管复合物进行表征,结果表明聚噻吩主链与碳纳米管通过π-π相互作用形成电荷转移复合物,聚噻吩侧链上的离子基团则赋予复合物良好的水溶性,从而均匀分散碳纳米管.与常用于分散碳纳米管的小分子表面活性剂十二烷基硫酸钠相比,相同质量的P3MHT可明显提高碳纳米管在水相中的溶度和均匀分散性.该复合物溶液具有非常高的稳定性,在静置6个月后复合物分散性基本保持不变.     

溶液结晶制备聚乙烯/碳纳米管串晶结构

通过等温以及非等温溶液结晶法制备了聚乙烯/碳纳米管复合串晶(shish-kebab)结构.电镜结果显示,等温结晶1 h得到的聚乙烯/碳纳米管串晶(shish-kebab)结构kebab长度为30~140 nm,kebab间间距为35~80 nm.使用非等温结晶法得到的产物kebab长度为40~180 nm,kebab间距与等温结晶过程得到的相同.此外实验发现聚乙烯/碳纳米管shish-kebab结构生长过程中,kebab的生长与新的kebab形成是同步发生,直至结晶结束.将得到的聚乙烯/碳纳米管shish-kebab结构在对二甲苯中静置3个月,光学图像显示仍能保持良好的分散性.使用沸腾对二甲苯冲洗聚乙烯/碳纳米管shish-kebab结构以验证其稳定性,发现冲洗过程中虽然部分聚乙烯链溶解,但仍有部分聚乙烯链吸附于碳纳米管上,并在降温过程中重新生成shish-kebab结构.     

嵌段共聚物溶液自组装制备纳米管状聚集体

作为一种新型材料,具有独特一维空心结构的纳米管受到了越来越多的关注。与研究较为广泛的碳纳米管和两亲性小分子纳米管相比,聚合物纳米管在尺寸范围、内外表面功能化及结构稳定性等方面具有优势。本文总结了嵌段共聚物在选择性溶剂中自组装形成纳米管状聚集体的最新研究进展。根据形成纳米管状结构的嵌段共聚物链段的性质,可将其划分为柔性-柔性嵌段共聚物、刚性-柔性嵌段共聚物,以及具备特殊结构的类嵌段共聚物三大类。针对每一类体系,重点归纳了管状结构的制备方法、结构表征和形成条件等研究现状,并概括总结了制备此类一维空心结构的理论依据。最后,对嵌段共聚物纳米管潜在的应用价值和今后可能的发展方向进行了展望。     

聚酯-聚酯多嵌段共聚物序列结构研究

利用对苯二甲酸乙二酯-己内酯多嵌段共聚物质子谱中各官能团的特征共振吸收峰计算证明两种吸收强度关系式反映了软链段和硬链段中相应官能团的数量关系,从而进一步肯定了所提出的链化学结构,在此基础上又直接利用各种官能团对其质子谱中特征吸收峰的强度贡献,计算得到多嵌段共聚物中软硬链段数,软硬链段平均长度,分子量和硬链段重量百分数的表示式。本文最后一部分用三素组的几率计算方法对多嵌段共聚物的质子谱和~(13)C谱分析讨论,所得有关链结构的数量关系是合理的,进一步证实了质子谱的直接计算法。     

单壁碳纳米管的控制生长与生长动力学

正结构决定性能,作为典型一维碳材料的单壁碳纳米管具有非常独特的光电性质,因而,单壁碳纳米管的结构控制制备一直是人们关注的热点问题,也成为该领域最具挑战的课题之一~(1,2)。目前,化学气相沉积方法是可控制备碳纳米管的主要方法,在化学气相沉积反应过程中,碳源在催化剂表面裂解成核,进而生长出结构不同、长度各异的单壁碳纳米管。为深入探索碳纳米管的生     

碳纳米管尺寸对电化学反应活性的影响

制备不同尺寸的多壁碳纳米管(MWNT)修饰电极,应用循环伏安法研究了相同管径、不同管长和相同管长、不同管径的多壁碳纳米管修饰电极在K3Fe(CN)6溶液中的电化学行为及其对尿酸、多巴胺等生物分子的电催化作用,以及尺寸效应对碳纳米管修饰电极电化学活性的影响规律.结果显示,在同一条件下,短管的MWNT比长管的更能有效促进K3Fe(CN)6的电子传递,更有利于对生物分子的电催化;管径对它的电化学行为及生物电催化活性影响较小,无明显规律.主要原因在于碳纳米管管端、管壁的不同电化学活性.     

Self-assembly behavior of carbon nanotubes modified by amphiphilic block copolymer

Block copolymers of poly(tert-butyl methyacrylate) (PtBMA) and polystyrene (PSt) were grafted onto multi-walled carbon nanotubes (MWNTs) by the reaction of azide groups at the copolymer chain end with the surface of MWNTs. After hydrolysis, PtBMA block was transformed to polymethyacrylic acid (PMAA) block, and amphiphilic diblock copolymer-modified MWNTs were finally obtained. The modified MWNTs were characterized by XPS, TGA, FTIR, and Raman, and the results showed that the amphiphilic diblock copolymers were grafted onto MWNTs by the covalent bond. The TEM and SEM observation showed that PMAA-b-PSt copolymer modified MWNTs (S2) formed self-assembly tube bundles with the size up to 20 μm in both ethanol and chloroform. However, PtBMA-b-PSt copolymer modified MWNTs (S1) only formed small-size aggregates or dispersed as single-modified MWNTs. The dispersion stability tests showed that S1 had good dispersion stability in several solvents (water, ethanol, acetone, and chloroform) even after 20 days. Due to the big-size tube bundles formed by self-assemble S2, the dispersion stability of S2 in above all solvents decreased, but it was still much better than that of pristine MWNTs.     

THERMAL DECOMPOSITION AND FLAMMABILITY OF ACRYLONITRILE-BUTADIENE-STYRENE/MULTI-WALLED CARBON NANOTUBES COMPOSITES

Thermal and flammability properties of acrylonitrile-butadiene-styrene copolymer (ABS) with the addition of multi-walled carbon nanotubes (MWNTs) were studied.ABS/MWNTs composites were prepared via melt blending with the MWNTs content varied from 0.2% to 4.0% by mass.Thermogravimetry results showed that the addition of MWNTs accelerated the degradation of ABS during the whole process under air atmosphere,and both onset and maximum degradation temperature were lower than those of pure ABS.The destabilizat...     

聚丙烯/多壁碳纳米管复合材料的热性能和流变性能

用熔融共混法制备了聚丙烯多壁碳纳米管(PP MWNTs)复合材料,TGA研究表明在氮气气氛下碳纳米管显著增加了聚丙烯基体的热稳定性.3wt%MWNTs可使PP热分解起始温度提高44℃.非等温结晶研究表明MWNTs对PP基体的结晶行为没有明显的影响.流变测试结果表明PP MWNTs复合材料的储能模量G′和损耗模量G″随着MWNTs含量增加逐渐增大.1wt%MWNTs的PP聚合物的零剪切粘度最低,5wt%MWNTs的PP聚合物的零剪切粘度最高,PP和3wt%MWNTs的PP纳米聚合物的零剪切粘度居于二者之间,随着频率的增加,剪切稀化作用越来越明显,呈现出假塑性流体行为.含5wt%MWNTs的PP复合材料的体积和表面电阻率与纯PP相比分别下降了9个和4个数量级,表明少量的MWNTs可以显著改变PP的电学性能.     

Effect of interaction between poly(ethylene terephthalate) and carbon nanotubes on the morphology and properties of their nanocomposites

Poly(ethylene terephthalate) (PET) nanocomposites were prepared by melt‐extruding mixtures of PET and functionalized multiwalled carbon nanotubes (MWNTs) with some interaction with PET molecules. For the functionalization of MWNTs, benzyl isocyanate and phenyl isocyanate with different molecular flexibility were employed on the surface of the MWNTs via chemical modification, respectively. The reaction for functionalization of MWNTs was confirmed by FTIR and transmission electron microscopy (TEM) measurements. TEM observations indicated that both benzyl and phenyl isocyanate groups covered the surface of the MWNTs after functionalization. The PET nanocomposites containing isocyanate groups showed improved mechanical properties, including the tensile strength and tensile modulus, compared with those with pristine and acid‐treated nanotubes. These improvements were ascribed to π–π interactions between the aromatic rings of PET molecules and the isocyanate group in MWNTs. The functionalized MWNTs showed a better dispersion of carbon nanotubes in the matrix polymer and a different fractured cross‐section morphology in scanning electron microscope measurements relative to the pristine MWNTs. The crystallinity of the functionalized MWNT‐PET nanocomposites was significantly higher than that of the pristine and acid‐treated MWNTs. FTIR results indicated that the presence of carbon nanotubes induced trans‐conformation of PET chains, and trans conformation was particularly dominant in PET composites incorporating MWNT‐phenyl. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 900–910, 2008     

Development of magnetic multiwalled carbon nanotubes combined with near-infrared radiation-assisted desorption for the determination of tissue distribution of doxorubicin liposome injects in rats

For the first time, magnetic multiwalled carbon nanotubes (MWNTs) combined with near-infrared radiation-assisted desorption (NIRAD) was successfully developed for the determination of tissue distribution of doxorubicin liposome injects (DOXLI) in rats. The magnetic MWNTs nanomaterials were synthesized via a simple hydrothermal process. Magnetic Fe(3)O(4) beads, with average diameters of ca. 200 nm and narrow size distribution, were decorated along MWNTs to form octopus-like nanostructures. The hybrid nanocomposites provided an efficient way for the extraction and enrichment of doxorubicin (DOX) via π-π stacking of DOX molecules onto the polyaromatic surface of MWNTs. DOX adsorbed with magnetic MWNTs could be simply and rapidly isolated through a magnetic field. In addition, due to the near-infrared radiation (NIR) absorption property of MWNTs, irradiation with NIR laser was employed to induce photothermal conversion, which could trigger rapid DOX desorption from DOX-loaded magnetic MWNTs. Extraction conditions such as amount of magnetic MWNTs added, pH values, adsorption time, desorption solvent and NIR time were investigated and optimized. Method validations including linear range, detection limit, precision, and recovery were also studied. The results showed that the proposed method based on magnetic MWNTs coupled to NIRAD was a simple, rapid and high efficient approach for the analysis of DOXLI in rat tissues.     

Preparation and properties of polysiloxane grafting multi‐walled carbon nanotubes/polycarbonate nanocomposites

Carboxyl multi‐wall carbon nanotubes (MWNTs‐COOH) were grafted by diaminopropyl terminated dimethylpolysiloxane (DPD) to the modified MWNTs‐COOH (MWNTs‐DPD). The surface structure and thermal stability of MWNTs‐DPD and MWNTs‐COOH were characterized using Fourier‐transform infrared spectroscopy, X‐ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). Then PC/MWNTs‐COOH and PC/MWNTs‐DPD nanocomposites were prepared by the solution method and melt extrusion method. The mechanical properties, transmission electron microscopy (TEM), TGA, limiting oxygen index (LOI), UL‐94 test, and permittivity test were used to evaluate the properties of the composites. The results showed that the MWNTs‐DPD was dispersed well in the PC matrix, and its tensile strength, flexual strength, flexural modulus, and flame retardancy were better than that of PC/MWNTs‐COOH. MWNTs‐DPD can improve the electrical properties of the nanocomposites at the low loading in PC. Copyright © 2010 John Wiley & Sons, Ltd.     

Decorating multi-walled carbon nanotubes with nickel nanoparticles for selective hydrogenation of citral

The nanocomposites of multi-walled carbon nanotubes (MWNTs) decorated with nickel nanoparticles were conveniently prepared by a chemical reduction of nickel salt in the present of poly(acrylic acid) grafted MWNTs (PAA-g-MWNTs). Due to the strong interaction between Ni²⁺ and –COOH, PAA-g-MWNTs became an excellent supporting material for Ni nanoparticles. The morphology and distribution of Ni nanoparticles on the surface of MWNTs were greatly influenced by the reduction temperatures, the experimental results also showed that the distribution of Ni nanoparticles was greatly improved while the MWNTs were modified by poly(acrylic acid) (PAA). The hydrogenation activity and selectivity of MWNTs decorated with Ni nanoparticles (Ni-MWNTs) for α, β-unsaturated aldehyde (citral) were also studied, and the experimental results showed that the citronellal, an important raw material for flavoring and perfumery industries, is the favorable product with a percentage as high as 86.9%, which is 7 times higher than that of catalyst by Ni-supported active carbon (Ni-AC).     

The combined catalytic action of solid acids with nickel for the transformation of polypropylene into carbon nanotubes by pyrolysis

The effects of both organically modified montmorillonite (OMMT) and Ni₂O₃ on the carbonization of polypropylene (PP) during pyrolysis were investigated. The results from TEM and Raman spectroscopy showed that the carbonized products of PP were mainly multiwalled carbon nanotubes (MWNTs). Surprisingly, a combination of OMMT and Ni₂O₃ led to high‐yield formation of MWNTs. X‐ray powder diffraction (XRD) and GC–MS were used to investigate the mechanism of this combination for the high‐yield formation of MWNTs from PP. Brønsted acid sites were created in degraded OMMT layers by thermal decomposition of the modifiers. The resultant carbenium ions play an important role in the carbonization of PP and the formation of MWNTs. The degradation of PP was induced by the presence of carbenium ions to form predominantly products with lower carbon numbers that could be easily catalyzed by the nickel catalyst for the growth of MWNTs. Furthermore, carbenium ions are active intermediates that promote the growth of MWNTs from the degradation products with higher carbon numbers through hydride‐transfer reactions. The XRD measurements showed that Ni₂O₃ was reduced into metallic nickel (Ni) in situ to afford the active sites for the growth of MWNTs.     

Cure kinetics of carbon nanotube/tetrafunctional epoxy nanocomposites by isothermal differential scanning calorimetry

The cure kinetics of tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) and 4,4′‐diaminodiphenylsulfone (DDS) as a cure agent in nanocomposites with multiwalled carbon nanotubes (MWNTs) have been studied with an isothermal differential scanning calorimetry (DSC) technique. The experimental data for both the neat TGDDM/DDS system and for epoxy/MWNTs nanocomposites showed an autocatalytic behavior. Kinetic analysis was performed with the phenomenological model of Kamal and a diffusion control function was introduced to describe the cure reaction in the later stage. Activation energies and kinetic parameters were determined by fitting experimental data. For MWNTs/epoxy nanocomposites, the initial reaction rates increased and the time to the maximum rate decreased with increasing MWNTs contents because of the acceleration effect of MWNTs. The values of the activation energies for the epoxy/MWNTs nanocomposites were lower than the values for the neat epoxy in the initial stage of the reaction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3701–3712, 2004