Polyaniline/Silver Nanoparticle-Doped Multiwalled Carbon Nanotube Composites

A simple method was used to synthesize the hybrid nanocomposites consisting of the functionalized multiwalled carbon nanotube composites (MWCNTs) with the polyaniline incorporated silver nanoparticles (a-MWCNT/PANI-Ag) through an emulsion polymerization at room temperature in order to enhance the electrical conductivity of polyaniline. The electrical conductivity of the composite with the incorporated Ag nanoparticles was 5% higher than the same weight percent for the composite without Ag nanoparticles, and the thermal stability was dramatically increased from 54% for the composite (a-MWCNT/PANI) to 69% through the incorporation of the Ag nanoparticles at 830°C. Additionally, the advantages of the Ag nanoparticles, including the improved electrical and thermal properties without damage to the polyaniline structure, were confirmed using FTIR and Raman spectroscopy.     

Hybrid Composite of Polyaniline Containing Carbon Nanotube

Among various conducting polymers, polyaniline (PANI) is a unique and promising candidate for practical applications because it is not only highly stable in air and in some solvents, but also exhibits dramatic changes in its electronic structure and physical properties in protoactivate state1,2,3. The carbon nanotubes (CNTs) have been proven to possess exotic properties, such as high mechanical strength, flexibility and electric conductivity. The study of carbon-based nanostructures and ma…     

Polymer Layered Silicate/Carbon Nanotube Nanocomposites: Morphological and Rheological Properties

Morphological and rheological properties of new ternary nanocomposites based on ethylene vinyl acetate copolymers (EVA), commercial organo-modified clays (organoclays) and purified multi-walled carbon nanotubes (MWNTs), prepared via direct melt blending, have been evaluated. For sake of comparison, the corresponding binary compositions, i.e., EVA filled with either organoclays or MWNTs, have been investigated as well. While extensive exfoliation can be observed for binary EVA/clay nanocomposites, the addition of MWNTs appears to limit clay exfoliation. Rheological properties show that both clay and MWNTs increase the elastic modulus of the nanocomposites, reflecting the high degree of nanoparticle interconnectivity that can be found in these materials.     

Rheological and Structure Investigation of Melt Mixed Multi-Walled Carbon Nanotube/PE Composites

In this study a series of melt mixed multi-walled carbon nanotube (MWNT)/Polyethylene composites with several carbon nanotube (CNTs) concentrations were investigated. A good dispersion of the nanotubes in the matrix was seen using scanning electron microscopy. Melt rheological measurements in dynamic mode were used to estimate the percolation state of the CNTs within the polymer and to provide information about the structure of the CNT/polymer composites. The effect of nanotubes on the non-isothermal crystallization behaviour of the nanocomposites was also studied by differential scanning calorimetry.     

Rheological Behavior of Spinning Dope of Multiwalled Carbon Nanotube/Polyacrylonitrile Composites

The spinning dope of Multiwalled carbon nanotube/polyacrylonitrile composites was prepared by in-situ polymerization in 50wt% NaSCN solution. The rheological behavior of the dope containing carbon nanotubes from 0.19wt% to 1.9wt% was investigated using rotational rheometry at 60°C.The nanotubes have diameters between 30-50nm and lengths ranging from 6 to 10 μm. The apparent viscosity decreases with the addition of carbon nanotubes; this can be explained by the inhibition of carbon nanotubes during polymerization progress. The spinning dope containing various contents of carbon nanotubes exhibits a shear thickening effect. However, the dynamic rheological test shows there is a peak of complex viscosity with the increasing in frequency.     

A Facile Approach to Single‐Wall Carbon Nanotube/Poly(allylamine) Nanocomposites

A facile approach to polymer nanocomposites with single‐wall carbon nanotubes and cationic polymers is reported. The composite material was synthesized by producing carboxylic acid groups at the nanotube termini followed by a reaction with poly(allylamine) in water. Fourier transform infrared spectral and thermogravimetric analyses corroborate that the poly(allylamine) chains were wrapped on the surface of the carbon nanotubes. The scanning electron microscopic (SEM) image shows that the nanotubes were dispersed with little aggregation, thus, strongly suggesting that the poly(allylamine) chains have covered the single‐wall carbon nanotubes, which was further evidenced by transmission electron microscopy. The composites are soluble in water, and this solubilization process opens up new opportunities in the solution chemistry on pristine nanotubes.

     

How a Zigzag Carbon Nanotube Grows

Owing to the unique structure of zigzag (ZZ) carbon nanotubes (CNTs), their ring‐by‐ring growth behavior is different from that of chiral or armchair (AC) CNTs, on the rims of which kinks serve as active sites for carbon attachment. Through first‐principle calculations, we found that, because of the high energy barrier of initiating a new carbon ring at the rim of a ZZ CNT, the growth rate of a ZZ CNT is proportional to its diameter and significantly (10–1000 times) slower than that of other CNTs. This study successfully explained the broad experimental observation of the lacking of ZZ CNTs in CNT samples and completed the theory of CNT growth.     

Thermal Degradation and Flammability Properties of Poly(propylene)/Carbon Nanotube Composites

Nanocomposites based on poly(propylene) and multi‐wall carbon nanotubes (up to 2 vol.‐%) were melt blended, yielding a good dispersion of nanotubes without using any organic treatment or additional additives. Carbon nanotubes are found to significantly enhance the thermal stability of poly(propylene) in nitrogen at high temperatures. Specifically, the nanotube additive greatly reduced the heat release rate of poly(propylene). They are found to be at least as effective a flame‐retardant as clay/poly(propylene) nanocomposites.     

多壁碳纳米管在精氨酸溶液中分散性的pH敏感性

通过非共价反应将精氨酸包覆于多壁碳纳米管上, 并用荧光分光光度计和原子力显微镜检测其在不同pH值条件下的分散性和凝聚性. 结果表明: 改性后的碳纳米管的分散性具有pH敏感性, pH值越大, 分散性越好, 且灵敏度高. 同时对其pH敏感性的机理进行了分析与讨论. 这将对碳纳米管在药物载送、生物传感等方面的应用有重要的意义.     

Electrostatic‐Assembly of Carbon Nanotubes (CNTs) and Polymer Particles in Water: a Facile Approach to Improve the Dispersion of CNTs in Thermoplastics

Summary: A facile and organic‐solvent‐free method for preparing thermoprocessable multiwalled carbon nanotube (MWCNT)‐filled thermoplastics is presented. MWCNTs are oxidized, neutralized, and then assembled with cationic soap‐free poly(methyl methacrylate) (PMMA) particles directly in water. The spontaneous electrostatic coupling between the negatively charged MWCNTs and positively charged PMMA particles, and the viscoelastic and thermomechanical behavior of the nanocomposites, are investigated. The electrostatic coupling interactions improve the dispersion of nanotubes and facilitate the formation of filler networks in the polymer matrix.

Preparation of nanocomposites of oxidized MWCNTs and positively charged PMMA particles through electrostatic assembly.     

Electrorheology of Multiwalled Carbon Nanotube/Poly(methyl methacrylate) Nanocomposites

Summary: Multiwalled carbon nanotube (MWNT) nanocomposites dispersed in a poly(methyl methacrylate) (PMMA) matrix were prepared via suspension polymerization, in which radicals induced on the outer wall of the MWNTs by 2,2′‐azoisobutyronitrile initiate the grafting of PMMA. The synthesized MWNT/PMMA nanocomposite particles were found to have a spherical shape and exhibit a high electrical conductivity, mainly as a result of the carbon nanotubes. A suspension was prepared with MWNT/PMMA particles in insulating silicone oil and its electrorheological properties were investigated by controlling applied direct current (DC) electric field strengths.

Flow curve possessing a region analogous to the coexistence curve.     

Growth Mechanism of Vertically Aligned Carbon Nanotube Arrays

Vertically aligned multi-walled carbon nanotube arrays grown on quartz substrate are obtained by co-pyrolysis of xylene and ferrocene at 850 oC in a tube furnace. Raman spectroscopy and high resolution transmission electron microscopy measurements show that the single-walled carbon nanotubes are only present on top of vertically aligned multi-walled carbon nanotube arrays. It has been revealed that isolated single-walled carbon nanotubes are only present in those floating catalyst generated materials. It thus suggests that the single-walled carbon nanotubes here are also generated by floating catalyst. Vertically alignedcarbon nanotube arrays on the quartz substrate have shown good orientation and good graphitization. Meanwhile, to investigate the growth mechanism, two bi-layers carbon nan-otube films with di erent thickness have been synthesized and analyzed by Raman spectroscopy. The results show that the two-layer vertically aligned carbon nanotube films grow “bottom-up”. There are distinguished Raman scattering signals for the second layer itself, surface of the first layer, interface between the first and second layer, side wall and bottom surface. It indicates that the obtained carbon nanotubes follow the base-growth mechanism, and the single-walled carbon nanotubes grow from their base at the growth beginning when iron catalyst particles have small size. Those carbon nanotubes with few walls (typically <5 walls) have similar properties, which also agree with the base-growth mechanism.     

In Situ Polymerized Carbon Nanotube/Polyimide Nanocomposites: Effect of Reaction Stoichiometry on the Glass Transition Properties of the Nanocomposites

A series of in situ polymerized CNT/PI nanocomposite materials synthesized at a fixed diamine‐to‐dianhydride monomer feed ratio with varying concentrations of added –COOH‐ functionalized CNT is studied. It is found that the glass transition temperature of the nanocomposite varies non‐monotonically with CNT concentration. To determine the origin of this behavior, the molecular weights of the matrix polymers are measured by the intrinsic‐viscosity method. The functional‐group density of the CNT material is determined by potentiometric titration. The results confirm that the glass transition of the CNT/PI system depends on the concentration of the CNT filler through its influence on the functional group stoichiometry and thus on the molecular weight of the polycondensation product.

     

高分子量聚苯胺/碳纳米管复合材料的合成与表征

在导电聚合物中,聚苯胺（PANI）因其导电性能优良,环境稳定性好,合成工艺简单,原料成本低廉等优点,被认为是最有可能实际应用的导电聚合物．然而用传统方法合成的聚苯胺由于其分子量小,分子链中存在缺陷而使其导电性能和力学性能大大降低,从而限制了其实际应用．而高分子量聚苯胺的导电性能和力学性能比一般聚苯胺有较大的提高．     

改性碳纳米管气体传感器

碳纳米管气体传感器具有灵敏度高、响应速度快、尺寸小和能在室温下工作等诸多优点,是一种很有前景的气体传感器.然而本征碳纳米管气体传感器只对少数几种气体如NH3、O2、NO2和SO2敏感,检测范围有限;而且这类传感器的检测灵敏度和选择性也有待提高.研究表明对碳纳米管进行改性可以克服这些缺陷.目前已有的改性方法主要包括对碳纳米管表面有机修饰、对碳纳米管掺入无机杂原子以及径向力学变形等.本文对改性碳纳米管气体传感器研究的最新进展进行了综述,分析了上述改性方法在扩大碳纳米管气体传感器的检测范围、提高检测灵敏度和选择性方面的优势和不足,并对其研究前景进行了展望.     

Polymorphism and Thermal Behaviour of Syndiotactic Poly(propylene)/Carbon Nanotube Composites

Summary: Nanocomposite materials were obtained by blending multi‐wall carbon nanotubes (CN), obtained by acetylene catalytic chemical vapour deposition (CVD) on Co/Fe‐modified NaY zeolite, with syndiotactic poly(propylene) (sPP). The nanotubes, well dispersed in the polymer matrix, favour the crystallization of the sPP helical chains and significantly improve the sPP thermal stability either in nitrogen or in air. The morphology of the sPP affects the behaviour of the sPP degradation in air.

Thermogravimetric analysis in air of pure sPP and the nanocomposite material.     

Introduction of Multiple Hydrogen Bonding for Enhanced Mechanical Performance of Polymer-Carbon Nanotube Composites

Due to their outstanding mechanical properties and high aspect ratios, carbon nanotubes (CNTs) are envisioned as attractive nanofillers in polymer composites. However, due to strong van der Waals interactions, deleterious aggregation of CNTs is typically observed in polymer nanocomposites. Moreover, due to low stress transfer between the matrix polymer and the nanotube filler, only limited reinforcement is obtained. We report here a novel functionalization strategy to obtain CNTs with pendant self-complementary hydrogen bonding groups in order to address these limitations. Multi-walled CNTs were functionalized with ureidopyrimidinone (UPy) groups, which display multiple hydrogen bonding. The functionalized CNTs were blended with acrylic copolymers containing pendant UPy moieties and significant enhancement in tensile performance of the nanocomposites was observed.     

电化学制备有序聚苯胺纳米线阵列

以有序碳纳米管阵列电极为基底电极,在硫酸或高氯酸溶液中,分别探明不同电化学聚合方法以及苯胺单体浓度对聚苯胺形貌的影响. 结果表明：采用循环伏安法无法制备出聚苯胺纳米线;而应用恒电位法虽可制得聚苯胺纳米线,但纳米线不能形成有序阵列;只有应用恒电流方法,并且以高浓度苯胺的高氯酸溶液作为聚合溶液,方能制得有序聚苯胺纳米线阵列.     

Achieving Direct Electrical Connection to Glucose Oxidase Using Aligned Single Walled Carbon Nanotube Arrays

Direct electron transfer between an electrode and the redox active centre of glucose oxidase, flavin adenine dinucleotide (FAD), is probed using carbon nanotube modified gold electrodes. Gold electrodes are first modified with a self‐assembled monolayer of cysteamine and then shortened single walled carbon nanotubes (SWNT) are aligned normal to the electrode surface by self‐assembly. The electrochemistry of these aligned nanotube electrode arrays is initially investigated using potassium ferricyanide which showed SWNT act as nanoelectrodes with the ends of the tubes more electrochemically active than the walls. Subsequently the nanotubes are plugged into the enzymes in one of two ways. In the first method, native glucose oxidase is covalently attached to the ends of the aligned tubes which allowed close approach to FAD and direct electron transfer to be observed with a rate constant of 0.3 s^?1. In the second strategy, FAD was attached to the ends of the tubes and the enzyme reconstituted around the surface immobilized FAD. This latter approach allowed more efficient electron transfer to the FAD with a rate constant of 9 s^?1.     

Electrocatalytic Dioxygen Reduction at Glassy Carbon Electrode Modified with Polyaniline Grafted Multiwall Carbon Nanotube Film

The work details the electrocatalysis of oxygen reduction reaction (ORR) in 0.5 M H₂SO₄ medium on a modified electrode containing a film of polyaniline (PANI) grafted multi‐wall carbon nanotube (MWNT) over the surface of glassy carbon electrode. We have fabricated a novel modified electrode in which conducting polymer is present as connected unit to MWNT. The GC/PANI‐g‐MWNT modified electrode (ME) is fabricated by electrochemical polymerization of a mixture of amine functionalized MWNT and aniline with GC as working electrode. Cyclic voltammetry and amperometry are used to demonstrate the electrocatalytic activity of the GC/PANI‐g‐MWNT‐ME. The GC/PANI‐g‐MWNT‐ME exhibits remarkable electrocatalytic activity for ORR. A more positive onset potential and higher catalytic current for ORR are striking features of GC/PANI‐g‐MWNT‐ME. Rapid and high sensitivity of GC/PANI‐g‐MWNT‐ME to ORR are evident from the higher rate constant (7.92×10² M^?1 s^?1) value for the reduction process. Double potential chronoamperometry and rotating disk and rotating ring‐disk electrode (RRDE) experiments are employed to investigate the kinetic parameters of ORR at this electrode. Results from RDE and RRDE voltammetry demonstrate the involvement of two electron transfer in oxygen reduction to form hydrogen peroxide in acidic media.