Matrix‐polymer‐functionalized multiwalled carbon nanotubes as a highly efficient toughening agent for matrix polymers

Matrix‐polymer‐functionalized multiwalled carbon nanotubes (MWCNTs) are demonstrated as a highly efficient toughening agent for matrix polymers. With poly(vinylidene fluoride) (PVDF) as the matrix polymer, the PVDF/MWCNT‐PVDF nanocomposite films show high toughness. With a small load amount of MWCNT‐PVDF (0.07 wt %), the nanocomposite film shows a yield point and a constant‐stress extension region in stress–strain tests, compared with the typical low‐extensibility feature of neat PVDF film. The PVDF/MWCNT‐PVDF‐0.7 film exhibits a 180‐fold increase of toughness and about 38‐fold increase in strain at break compared with neat PVDF film. This toughening effect is attributed to (a) homogeneous dispersion of MWCNT‐PVDF in PVDF, (b) the high efficiency of load‐transfer across MWCNT/PVDF interface, and (c) the long length of the MWCNTs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

复合方式对MWCNTs/TiO2纳米复合薄膜光电化学性能的影响

采用溶胶-凝胶法制备了不同复合方式的系列多壁碳纳米管(multi-walled carbon nanotubes, MWCNTs)/TiO2纳米复合薄膜电极. 通过SEM表征了薄膜的表面形貌, 并测定了MWCNTs引入前后对TiO2晶型结构和光吸收性能的影响以及不同复合方式的纳米复合薄膜的光电化学特性. 结果表明, MWCNTs/TiO2纳米复合薄膜表面形成无序多孔的形貌, 其光谱吸收边可拓展到可见光区; MWCNTs底层分布的纳米复合薄膜比纯TiO2表现出更好的光电活性, 而MWCNTs在表层分布及均匀分布的纳米复合薄膜的光电活性相对较差. 依据载流子分离原理探讨了不同复合方式对纳米复合薄膜光电性能的影响, 底层分布MWCNTs的纳米复合薄膜由于MWCNTs有效地收集传递电子并阻止载流子的复合从而提高了光电化学活性.     

Nonenzymatic glucose voltammetric sensor based on gold nanoparticles/carbon nanotubes/ionic liquid nanocomposite

In this paper, a novel nonenzymatic glucose voltammetric sensor based on a kind of nanocomposite of gold nanoparticles (GNPs) embedded in multi-walled carbon nanotubes (MWCNTs)/ionic liquid (IL) gel was reported. The surface morphology of this nanocomposite was characterized using X-ray photoelectron spectrometer (XPS), scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. It can be found that most of GNPs lie close to the ektexine of MWCNTs and the others have obviously inserted the inner of MWCNTs through the defects or ends of MWCNTs, due to the attraction between GNPs and MWCNTs as well as the repulsion between GNPs and IL. Voltammetry was used to evaluate the electrocatalytic activities of the nanocomposite biosensor toward nonenzymatic glucose oxidation in alkaline media. The GNPs embedded in MWCNTs/IL gel have strong and sensitive voltammetric responses to glucose, owing to a possible synergistic effect among GNPs, MWCNTs and IL. Under the optimal condition, the linear range for the detection of the glucose is 5.0-120 μM with the correlation coefficient of 0.998, based on the oxidation peak observed during cathodic direction of the potential sweep. The kinetics and mechanism of glucose electro-oxidation were intensively investigated in this system. This kind of nanocomposite biosensor is also highly resistant toward poisoning by chloride ions and capable of sensing glucose oxidation in the presence of 20 μM uric acid and 70 μM ascorbic acid. This work provides a simple and easy approach to the detection of glucose in body fluid with high sensitivity and excellent selectivity.     

Electroanalysis of Bisphenol A at a Multiwalled Carbon Nanotubes‐gold Nanoparticles Modified Glassy Carbon Electrode

A sensitive electrochemical method was developed for the determination of bisphenol A (BPA) at a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (MWCNTs)‐gold nanoparticles (GNPs) hybrid film, which was prepared based on the electrostatic interaction between positively charged cetyltrimethylammonium bromide (CTAB) and negatively charged MWCNTs and GNPs. The MWCNT‐GNPs/GCE exhibited an enhanced electroactivity for BPA oxidation versus unmodified GCE and MWCNTs/GCE. The experimental parameters, including the amounts of modified MWCNTs and GNPs, the pH of the supporting electrolyte, scan rate and accumulation time, were examined and optimized. Under the optimal conditions, the differential pulse voltammetric anodic peak current of BPA was linear with the BPA concentration from 2.0×10^?8 to 2×10^?5 mol L^?1, with a limit of detection of 7.5 nmol L^?1. The proposed procedure was applied to determine BPA leached from real plastic samples with satisfactory results.     

FTIR Spectroscopic Study of Crystallization of Uniaxial Drawn Syndiotactic Polystyrene/Carbon Nanotube Nanocomposite Films

The crystallization of uniaxial hot drawn syndiotactic polystyrene/multi-walled carbon nanotube (sPS/MWCNT) nanocomposite films was studied by FTIR spectroscopy. The effects of MWCNT content, draw ratio and drawing temperature on the sPS crystallinity were investigated. The sPS/MWCMT nanocomposite films show reduced crystallinities with the increase of MWCNT content. In addition, with the increase of draw ratio, both the pure sPS and the sPS/MWCNT nanocomposite drawn films exhibit increased crystallinity. The effect of drawing temperature on the sPS crystallization is complex. In a temperature range of 100―135 ℃, the crystallinity decreases with drawing temperature, whereas it increases at 140 ℃ for both pure sPS and its nanocomposite films.     

Synthesize procedures, mechanical and thermal properties of thiazole bearing poly(amid-imide) composite thin films containing multiwalled carbon nanotubes

This research is aimed at characterizing the thermal, mechanical, and morphological properties of carbon nanotubes (CNTs) reinforced poly(amide-imide) (PAI) composites having thiazol and amino acid groups which were prepared by sonication-assisted solution compounding. To increase the compatibility between the PAI matrix and CNTs, carboxyl-functionalized multiwall CNTs (MWCNTs-COOH) were used in this study. The MWCNTs were dispersed homogeneously in the PAI matrix while the structure of the polymer and the MWCNTs structure are stable in the preparation process as revealed by transmission electron microscopy. MWCNT/PAI composite films have been prepared by casting a solution of precursor polymer containing MWCNTs into a thin film, and its tensile properties were examined. The thermal stability, Young’s modulus, and tensile strength of PAI were greatly improved by the incorporation of MWCNTs and their good dispersion. Composites were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermal gravimetric analysis.     

水溶性多壁碳纳米管/铜酞菁染料自组装薄膜的制备与表征

Water soluble multi-wall carbon nanotubes (MWCNTs) were prepared via chemical oxidation. Under ultrasonication,the chemically treated MWCNTs can be dispersed in water to form colloids. The MWCNTs were characterized by FT-IR spectra. The FT-IR spectra reveal the presence of carboxylic groups on the nanotubes. The functional groups can improve the nanotubes-solubility in water. Alcian Blue 8GX (AB), a quaternary ammonium dye of the copper phthalocyanine group, was dissolved in water and used to form electrostaticcally self-assembled multilayer films. The MWCNT/AB composite films were characterized by UV-vis absorption spectra as well as AFM and fluorescence spectrum. The experimental results show that the MWCNT/AB composite films can be produced easily. Compared to those of the AB aqueous solutions, composite films exhibit pronounced differences in the absorption and fluorescence spectra, which suggests that AB molecules aggregated in the composite film, and that a charge transfer might exist between AB molecules and the MWCNTs.     

Deformable strain sensors based on patterned MWCNTs/polydimethylsiloxane composites

Patterned MWCNT/polydimethylsiloxane (PDMS) nanocomposite strain sensors were achieved by a microelectromechanical system assisted electrophoretic deposition (EPD) technique. With the combined effect of superior intrinsic piezoresistivity of the individual MWCNT and the tunneling effect of the MWCNT network, the stretchable composite demonstrates high sensitivity to the tensile strain. The gauge factor shows a strong dependence on both the initial resistance of the CNT/PDMS composite and the applied strain level. The mechanism is elucidated by analyzing the structure‐property‐function of patterned CNT networks. When the entanglement of a MWCNT network allows effective load transfer, the sensitivity is primarily dominated by the intrinsic piezoresistivity of individual MWCNTs. Conversely, when the MWCNTs interpenetrate loosely, the tunneling effect prevails. The sensitivity of the device can be tailored by the proposed technique since MWCNT film thickness/density can be readily controlled by means of the patterning parameters of the EPD process. The work provides useful guidance for design and development of strain/stress sensors with targeted sensitivity for flexible electronics applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1505–1512     

Core–shell functionalized MWCNT/poly(m‐aminophenol) nanocomposite with large dielectric permittivity and low dielectric loss

Core–shell carboxyl‐functionalized multiwall carbon nanotube (c‐MWCNT)/poly(m‐aminophenol) (PmAP) nanocomposite were prepared through in‐situ polymerization of m‐aminophenol (m‐AP) in the presence of MWCNTs, and explicated as a dielectric material for electronic applications. The formation of thin PmAP layer on individual c‐MWCNT with excellent molecular level interactions at interfaces was confirmed by morphological and spectroscopic analyses. Here we conducted a comparative study of the dielectric performances of PmAP based nanocomposite films with pristine MWCNTs and c‐MWCNTs as fillers. Compared to PmAP/MWCNT nanocomposites, the PmAP/c‐MWCNT nanocomposites exhibited higher dielectric permittivity and lower dielectric loss. The well dispersed c‐MWCNTs in PmAP/c‐MWCNT nanocomposite produce huge interfacial area together with numerous active polarized centers (crystallographic defects), which in turn intensified the Maxwell‐Wagner‐Sillars (MWS) effect based on excellent molecular level interactions and thus, produce large dielectric permittivity (8810 at 1 kHz). The percolation threshold of PmAP/c‐MWCNT nanocomposites is found lower than that of the PmAP/MWCNT nanocomposites, which could be attributed to homogeneous distribution of c‐MWCNTs and strong c‐MWCNT//PmAP interfacial interactions in the nanocomposites. Copyright © 2016 John Wiley & Sons, Ltd.     

Surfactant dispersed multi-walled carbon nanotube/polyetherimide nanocomposite membrane

Carbon nanotube based nanocomposite membranes have been fabricated through solution casting by embedding multi-walled carbon nanotubes (MWCNTs) within polyetherimide (PEI) polymer host matrix. In order to achieve fine dispersion of nanotubes and facilitate strong interfacial adhesion with the polymer matrix, the nanotubes were first treated with surfactants of different charges, namely anionic sodium dodecyl chloride, cationic cetyl trimethyl ammonium chloride and non-ionic Triton X100, prior to the dispersion in the PEI dope solution. Dispersion of MWCNTs in N-methyl-2-pyrrolidone solvent showed that the agglomeration and entanglement of the nanotubes were greatly reduced upon the addition of Triton X100. Scanning electron microscopy and atomic force microscopy examination has evidenced the compatibility of Triton X100 dispersed MWCNTs with the polymer matrix in which a promising dispersion and adhesion has been observed at the MWCNT-PEI interface. The increase in both thermal stability and mechanical strength of the resulting Triton X100 dispersed MWCNT/PEI nanocomposite indicated the improved interaction between MWCNTs and PEI. This study demonstrated the role of Triton X100 in facilitating the synergetic effects of MWCNTs and PEI where the resulting composite membrane is anticipated to have potential application in membrane based gas separation.     

Electrical and humidity characterization of m-NA doped Au/PVA nanocomposites

The Meta-Nitroaniline (m-NA) doped (by varying weight percentage (wt. %)) gold/polyvinyl alcohol (Au/PVA) nanocomposites were synthesized using gold salt and hydrazine hydrate (HH) by in situ process. The composite was coated on ceramic rods having two end electrodes by drop casting method for studying their electrical behavior at different relative humidity (RH) levels, ranging from 4 to 95% RH at room temperature. The optimized wt. % was used to prepare coatings of various thicknesses (20-40 μm) of the films. As the humidity decreases, the resistance increases. The low humidity sensing characteristic can be tailored by varying wt. % of m-NA and thicknesses of the nanocomposite films. The resistive-humidity sensor shows two regions of sensitivity having highest sensitivity for lower RH. The sensor response and recovery time is about 6-10 s and 52 s respectively. The dynamic range of variation of the resistance allows a promising use of the films as a humidity sensor. The material was characterized by X-ray diffraction (XRD) and impedance spectroscopy at 60% RH.     

Investigating properties of poly (ether‐amide)/MWCNT nanocomposite films containing 2,7‐bis(4‐aminophenoxy)naphthalene and isophthalic segments

Three nanocomposite films based on aramid (poly (ether‐amide), PEA) and multiwall carbon nanotubes (MWCNT) were prepared via solution casting method using 2,7‐bis(4‐aminophenoxy)naphthalene (4) and isophthalic acid (5) containing various amounts of MWCNT (2, 3, 5 wt.%). To comprehensively analyze the properties of the cast films as well as the monomers, different techniques were employed, namely FT‐IR, ¹H NMR, X‐ray diffraction, and field emission scanning electron microscopy. Also, thermal and tensile properties of PEA (6) and nanocomposite films were investigated using thermogravimetric analysis and mechanical analysis, respectively. The morphology, thermal, and mechanical properties of nanocomposite films approved that MWCNT had well dispersion in the PEA matrix and showed a synergistic effect on improving all of the investigated properties. Based on the thermogravimetric analysis results, employing MWCNT caused to increase in the char yields from 61 (in the neat PEA) to 66 (in the PEA /MWCNT nanocomposite 5 wt.%) under the nitrogen atmosphere. In comparison to the pristine PEA (426°C), the temperature at 10 losses mass % (T₁₀) was increased from 530°C to 576°C, with 2 to 5 wt.% of MWCNT. Mechanical analysis revealed that the tensile strength and initial modulus were improved by incorporating MWCNT into PEA (81.70–93.40 MPa and 2.10–2.22 GPa, respectively). Electrical conductivity of the PEA/MWCNT nanocomposites was displayed maximum value in the 5 wt.%, showing satisfactory value in many application areas. The X‐ray diffraction technique was employed to study the crystalline structure of the prepared nanocomposite films as well as PEA. In addition, the electrochemical impedance spectroscopy study demonstrated that the prepared nanocomposites had significant impedance improvement in the presence of MWCNTs.     

Highly Selective and Sensitive Detection of Dopamine in the Presence of Excessive Ascorbic Acid Using Electrodes Modified with C60‐Functionalized Multiwalled Carbon Nanotube Films

Electrochemical detection of dopamine (DA) in the presence of a large excess of ascorbic acid (AA) was investigated with a novel all‐carbon nanocomposite film of C₆₀‐MWCNTs (C₆₀‐functionalized multi‐walled carbon nanotubes) using a bare MWCNTs film as control. Although both films can selectively detect DA from AA by separating their oxidation potentials, the C₆₀‐MWCNTs film shows special selectivity and good sensitivity for detecting DA. On one hand, the C₆₀‐MWCNTs composite film shows a higher activity for DA oxidation with enhanced peak current. On the other hand, the C₆₀‐MWCNTs composite film effectively suppresses the oxidation of AA. Remarkably, it is found that the oxidation current of DA is over 2 times higher than that of AA even when the concentration of AA is about 3 to 4 orders of magnitude higher than that of DA. This offers a tremendous advantage for the simple and clean detection of DA free of the interfering AA signal in a real assay. Cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectrometry are used to characterize the C₆₀‐MWCNTs composite film. These novel properties are interpreted to arise from the facile electron transfer between C₆₀ and MWCNTs in the C₆₀‐MWCNTs nanocomposite film.     

多壁碳纳米管对聚甲醛性能的影响

将多壁碳纳米管(MWCNTs)和聚甲醛(POM)在转矩流变仪中熔融混合得到POM/MWCNT复合材料.研究了复合材料的形态,导热性能,导电性能,流变性能和结晶性能.结果表明,MWCNTs在没有经过处理的情况下能够均匀地分散在POM基体中;当向POM中添加1.0 wt%含量MWCNTs时,复合材料的导热系数上升到0.5289 W/(K m),比纯POM的导热系数0.198 W/(K m)提高1.5倍,通过有效介质方法(EMA)验证了体系导热系数提高幅度不大的原因是MWCNTs与POM之间形成了很高的界面热阻;当MWCNTs的含量为1.0 wt%时,体系产生了导电逾渗效应,逾渗值在0.5 wt%~1.0 wt%之间;MWCNTs对POM有显著的成核作用,当向POM中添加0.5 wt%含量的MWCNTs时,POM的结晶温度提高6℃左右,但当MWCNTs的添加量进一步增加时,结晶温度几乎不再变化,成核效果呈现"饱和"状态.另外,材料的复数黏度,储能模量和损耗模量随MWCNTs含量的增加而增加.     

Polypyrrole–multi-walled carbon nanotube nanocomposites synthesized in oil–water microemulsion

An oil–water microemulsion system, having been successfully used for synthesizing polypyrrole (PPy) nanoparticles, is introduced for preparing PPy–multi-walled carbon nanotube (MWCNT) nanocomposites via in situ chemical oxidative polymerization. The structures and the physical properties of the PPy–MWCNT nanocomposites are also investigated. The studies show that PPy can coat MWCNTs to form core–shell structure. The backbone structure of PPy is not damaged by the introduction of MWCNTs, and the PPy in the PPy–MWCNT nanocomposites is still amorphous as pure PPy. The conductivities of PPy–MWCNT nanocomposites are higher than that of pure PPy and are enhanced with the increase in the MWCNT–monomer mass ratio. Furthermore, a model is supposed to be used for illustrating the mechanism for PPy–MWCNT nanocomposite formation via in situ microemulsion synthesis.     

Dye-sensitized solar cells based on multiwalled carbon nanotube-titania/titania bilayer structure photoelectrode

Dye-sensitized solar cells (DSSCs) were fabricated using multiwalled carbon nanotube (MWCNT)-TiO(2) nanocomposite as a light scattering layer. Morphology of the MWCNT-TiO(2) film was investigated by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). FESEM and TEM images demonstrate that MWCNTs and TiO(2) nanoparticles can be dispersed with chitosan. Internal resistance in the DSSC was characterized by electrochemical impedance spectroscopy (EIS). EIS results reveal a decrease in the charge resistance of electrolyte/dye/MWCNT-TiO(2)/TiO(2) interface with increasing MWCNT content up to 3 wt% which leads to an improvement in the photovoltaic performance. Compare with a nanocrystalline TiO(2) single-layer cell, the DSSC based on the MWCNT (3 wt%)-TiO(2)/TiO(2) bilayer structure photoelectrode shows ~100% increase in solar-to-electric energy conversion efficiency, which is attributed to the inclusion of MWCNTs in TiO(2) matrix.     

Preparation of polymer nanocomposites with enhanced mechanical properties using hybrid of graphene and partially wrapped multi-wall carbon nanotube as nanofiller

Triblock copolymer of poly(p-dioxanone) and polyethylene glycol end-capped with pyrene moieties ((Py-PPDO)₂-b-PEG) was synthesized and used as modifier for multi-wall carbon nanotubes (MWCNTs). Nano-aggregates ((Py-PPDO)₂-b-PEG@MWCNTs) with shish-kebab like partially wrapped morphology and very good stability were obtained by incorporating the copolymer with MWCNTs. The bare MWCNT sections of (Py-PPDO)₂-b-PEG@MWCNTs were able to induce π-π interactions with graphene (GE) and resulted in a novel GE/(Py-PPDO)₂-b-PEG@MWCNTs hybrid. The dispersity of GE in solution or polymer matrix was therefore greatly improved. The PCL nanocomposite films using GE/(Py-PPDO)₂-bPEG@MWCNTs as hybrid nanofiller exhibited obviously improved mechanical properties especially at very low hybrid nanofiller content. The influence of the nanofiller content and feed ratio of GE/MWCNTs on the mechanical properties of composites films was evaluated. When the feed ratio of GE to MWCNTs is 2:8 and the total loading of nanofiller is only 0.01 wt%, the tensile strength of the composite film increased by 163% and the elongation at break increased by 17% compared to those of neat PCL. These results can be attributed to fine dispersion of the nanofillers in PCL matrix and the hybrid interactions between GE and MWCNTs. Therefore, this work provides a novel method for preparing polymer nanocomposites with high mechanical performance and low nanofiller loading.     

Experimental fracture study of MWCNT/epoxy nanocomposites under the combined out-of-plane shear and tensile loading

In order to explore the role of multi-walled carbon nanotubes (MWCNTs) on the fracture behavior of epoxy-based nanocomposites, fracture tests were conducted under the combined out-of-plane shear and tensile loading. Epoxy resin LY-5052 together with MWCNT contents of 0.1, 0.5 and 1.0 wt% were used to produce nanocomposite specimens. The results showed that increasing the contribution of out-of-plane shear from pure mode I towards pure mode III enhanced fracture toughness for both pure epoxy and nanocomposites. Additionally, it was found that in both loading conditions of pure mode III and mixed mode I/III, increasing MWCNT content up to 1.0 wt% enhanced fracture toughness with an ascending trend. The mechanisms involved in the fracture behavior of polymer-based nanocomposites were also studied in detail using the photographs taken from the fracture surfaces by scanning electron microscopy.     

Evaluation of co-polyaniline nanocomposite thin films as humidity sensor

Spin coated films of Co-Polyaniline nanocomposite are evaluated for their transmission properties using He-Ne laser for humidity sensing. The thickness (17-29 microm) of the films is varied by multiple deposition of Co-Polyaniline nanocomposite on a glass substrate. The samples exhibit typically two to three regions in their sensitivity curve when tested in the relative humidity (RH) range of 20-95%. The sensitivity ranges from 0.1 mV/%RH to 12.26 mV/%RH for lower to higher thickness. The sensors show quick response of 8s (20-95%RH), and a recovery time of 1 min (95-20%RH) with good repeatability, reproducibility and low hysteresis effect. The sensitivity of the sensor increases with humidity and thickness. Material characterization is done by X-ray diffraction (XRD), scanning electron micrograph (SEM) and Fourier transform infra-red spectroscopy (FTIR).