Electrical and rheological percolation of PMMA/MWCNT nanocomposites as a function of CNT geometry and functionality

Composites of poly(methyl methacrylate) (PMMA) with multi-walled carbon nanotubes (MWCNT) of varying aspect ratio and carboxylic acid functionality were prepared using melt mixing. The extent of dispersion and distribution of the MWCNTs in the PMMA matrix was investigated using a combination of high-resolution transmission electron microscopy (HRTEM), wide-angle X-ray diffraction (XRD) and Raman spectroscopy. The electrical resistivity and oscillatory shear rheological properties of the composites were measured as a function of MWCNT geometry, functionality, and concentration. The fundamental ballistic conductance of the pristine free-standing MWCNTs was investigated using a mechanically controlled break-junction method. The electrical conductivity of PMMA was enhanced by up to 11 orders of magnitude for MWCNT concentrations below 0.5 wt.%. MWCNTs having higher aspect ratio, above 500, or functionalized with carboxylic acid groups readily formed rheological percolated networks with thresholds, determined from a power law relationship, of 1.52 and 2.06 wt.%, respectively. The onset of pseudo-solid-like behaviour and network formation is observed as G′, η∗, and tan δ⁻¹ are independent of frequency as MWCNT loading increased. Sufficiently long and/or functionalized tubes are required to physically bridge or provide interfacial interactions with PMMA to alter polymer chain dynamics. Carboxylic acid functionalization disrupts the crystalline order of MWCNTs due to a loss of π-conjugation and electron de-localisation of sp² C-C bonds resulting in non-ballistic electron transport in these tubes, irrespective of how highly dispersed they are in the PMMA matrix.     

Ultrasonic assisted polyol synthesis of highly dispersed Pt/MWCNT electrocatalyst for methanol oxidation

A novel chemical method based on ultrasonic assisted polyol synthesis for the fabrication of highly dispersed Pt nanoparticles on multi-walled carbon nanotubes (MWCNTs) was developed. The simple and green method took only about 10 min at ambient temperature. The structure and chemical nature of the resulting Pt/MWCNT composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDS). The results showed that the prepared Pt nanoparticles were uniformly dispersed on the MWCNT surface. The mean size of Pt nanoparticles was about 2.8 nm. Electrochemical properties of Pt/MWCNT electrode for methanol oxidation were examined by cyclic voltammetry (CV) and excellent electrocatalytic activities could be observed. The possible formation mechanism of Pt/MWCNTs was also discussed.     

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.     

Rheological and electrical properties of polypropylene/MWCNT composites prepared with MWCNT masterbatch chips

Melt compounded PP/MWCNT (polypropylene/multi-walled carbon nanotube) composites were prepared by diluting highly concentrated masterbatch chips. Maleic anhydride grafted polypropylene (PP-g-MAH) was used as a compatibilizer to promote dispersion and interaction of MWCNTs. Rheological properties were investigated with respect to the MWCNT and compatibilizer loadings, and related to morphological and electrical properties. As the MWCNT loading was increased, shear viscosity and yield stress were increased at low shear rate region because of increased interaction between MWCNT particles. When the MWCNT loading was low, MWCNT dispersion was improved by the PP-g-MAH compatibilizer because MWCNTs were wetted sufficiently due to the presence of the compatibilizer. However, rheological and electrical properties of highly concentrated MWCNT composites with the compatibilizer were not improved compared with PP/MWCNT composites without the compatibilizer because the compatibilizer did not provide sufficient wrapping of MWCNT particles. Electrical and morphological properties of PP/MWCNT composites were correlated with the rheological properties in steady and dynamic oscillatory shear flows.     

Cut growth and abrasion behaviour,and morphology of natural rubber filled with MWCNT and MWCNT/carbon black

Various amounts of predispersed multi-wall carbon nanotubes (MWCNT) were mixed with natural rubber (NR), with and without carbon black (CB), for preparing MWCNT-filled NR (NC) and MWCNT/CB-filled NR (NH) vulcanizates. All NH vulcanizates contained 30 phr CB and the amount of MWCNT for both NC and NH was varied from 0 to 8 phr. Helium ion microscopy (HIM) and FE-SEM images showed that MWCNT in the NH was dispersed much better than in the NC. Additionally, the well dispersed CB and MWCNT in the NH functioned synergistically in promoting an increase in longitudinal crack growth, leading to enhancement of edge-cut tensile strength (CTS) with increasing MWCNT loading. In contrast, all NC specimens ruptured in a simple lateral direction relating to their lower CTS. Results also revealed that abrasion resistance of the NH was not significantly changed with increasing MWCNT, whereas that of the NC increased. Nevertheless, abrasion resistance of both vulcanizates showed good correlation with the average value of ridge spacing on their abraded surfaces. It was also found that tensile strength of the NH was almost unchanged when the MWCNT loading was increased because the reinforcement by CB predominates over the MWCNT. However, 100% modulus and hardness of both NC and NH increased with increasing MWCNT content.     

Influence of MWCNT morphology on dispersion and thermal properties of polyethylene nanocomposites

In this study a series of multi-walled carbon nanotube (MWCNT)/Polyethylene (PE) composites with different kinds and several concentrations of carbon nanotubes (CNTs) were investigated. The morphology and degree of dispersion of the fillers in the polymer matrix at different length scales was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Both individual and agglomerated MWCNTs were evident but a good dispersion was observed for some of them. TGA measurements were performed on nanocomposites in order to understand if CNTs affect the stabilization mechanism during thermal and oxidative degradation. The analysis demonstrates that MWCNTs presence slightly delays thermal volatilisation (15-20 °C) without modification of thermal degradation mechanism. In contrast, thermal oxidative degradation in air is delayed up to about 100 °C dependently from MWCNTs concentration, in the range used here (0.1-2.0 wt%), and degree of dispersion. The stabilization is due to the formation of a thin protective layer of entangled MWCNTs kept together by carbon char generated on the surface of the nanocomposites as shown by SEM images taken on degradation residues.     

Phase morphology of iPP/aPS/SEP blends

Supermolecular structure and phase morphology of the ternary isotactic polypropylene/atactic polystyrene/poly(styrene-b-ethylene-co-propylene) (iPP/aPS/SEP) compression molded blends with 100/0, 90/10, 70/30, and 50/50 iPP/aPS weight ratios and with different amounts of added SEP compatibilizer were studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). SEP significantly reduced the size of dispersed aPS particles that enabled better spherulitization in the iPP matrix. Furthermore, iPP spherulites in ternary blends with 90/10 iPP/aPS weight ratio became larger in comparison with the pure iPP. TEM revealed that the SEP formed continuous interface layer around the dispersed aPS particles even when only 2.5 wt.% of SEP was added. Particle size distribution was distinctly bimodal. When the SEP content was increased to 10 wt.%, joining together smaller and bigger aPS and SEP particles formed dispersed aggregates. Additionally, both amorphous components (aPS and SEP) influenced crystallization process of iPP matrix and so modified, to some extent, its final supermolecular structure. SEP compatibilizer did not significantly affect crystallite orientation. The increase of crystallite sizes, which was more affected by the addition of aPS than by the addition of SEP, seemed to be influenced by the solidification effect rather than by the phase morphology of the blends.     

Poly(methyl methacrylate)/multiwalled carbon nanotube microspheres fabricated via in‐situ dispersion polymerization

Poly(methyl methacrylate)/multiwalled carbon nanotube (PMMA/MWCNT) microspheres were successfully prepared by in situ dispersion polymerization in an alcohol phase in which the acid‐treated MWCNTs were dispersed before polymerization. The PMMA and PMMA/MWCNT microspheres were monodisperse. The diameters of the microspheres decreased from about 11.6–6.0 μm as the MWCNT content was increased from 0 to 0.03 wt %. The morphology of the PMMA/MWCNT microspheres was investigated by scanning electron microscopy, atomic force microscopy, and transmission electron microscopy, and the experimental results showed that the MWCNTs were present both in the interior and on the surface of the microspheres. The synthesized PMMA/MWCNT microspheres were also characterized by electrical resistance measurements to analyze their electrical conductivity. They showed electrorheological (ER) fluid characteristics when they were dispersed in silicone oil. Their ER properties were confirmed by using optical microscopy to examine a suspension of the PMMA/MWCNT microspheres dispersed in insulating silicone oil to which an electric field of 2.5 kV/cm was applied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 182–189, 2008     

Crystallization Behavior and Mechanical Properties of Poly(vinylidene fluoride)/multi-walled Carbon Nanotube Nanocomposites

Poly(vinylidene fluoride)(PVDF)/multi-walled carbon nanotube(MWCNT) nanocomposites were prepared by means of ultrasonic dispersion method. X-ray diffraction(XRD) results indicate that incorporating MWCNTs into PVDF caused the formation of β phase. A thermal annealing at 130 °C confirmed that the β phase was stable in the nanocomposites. Differential scanning calorimetry(DSC) results indicate that the melting temperature slightly increased while the heat of fusion markedly decreased with increasing MWCNT content. The tensile strength and modulus of PVDF were improved by loading the MWCNTs. The scanning electron microscopy(SEM) observations showed that MWCNTs were uniformly dispersed in the PVDF matrix and an interfacial adhesion between MWCNT and PVDF was achieved, which was responsible for the enhancement in the tensile strength and modulus of PVDF.     

Thermal and electrical behaviors of acid functionalized MWCNT/ABC-type triblock copolymer grafted-MWCNT nanocomposites

In this work, ABC-type triblock copolymer grafted onto the surface of the MWCNT/acid functionalized MWCNT (MWCNT-COOH) composites were prepared and the properties of nanocomposites were characterized extensively using differential scanning calorimetry (DSC), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), ac electrical conductivity and dielectrical measurements.

DSC study showed that the glass transition temperatures of the nanocomposites are a some higher than that of the matrix polymer. The increase in oxidized MWCNT in the nanocomposite improved the thermal stability of the composite, according to initial decomposition temperatures. The ac electrical conductivity has increased moderately with increasing frequency, but has increased slowly with increase in the oxidized MWCNT content in the nanocomposites. The electrical conductivity increases slowly with increasing temperature to about the glass transition temperature, then it increases faster. The dielectric constants for the matrix polymer and all the composites decreases slightly with increasing frequency from 0.1 kHz to 2.0 kHz. The dielectric constant increases slightly with increasing temperature up to about the glass transition temperature region and then the increase in temperature is accelerated the increase in the dielectric constant.     

Influence of organo-clay on electrical and mechanical properties of PP/MWCNT/OC nanocomposites

The electrical, thermal and mechanical properties of nanocomposites, based on polypropylene (PP) filled by multi-walled carbon nanotubes (MWCNTs) and organo-clay (OC), were studied with the purpose of finding out the effect of OC on the microstructure of MWCNTs dispersion and PP/MWCNT/OC composites. It was found that addition of organo-clay nanoparticles improved nanotube dispersion and enhanced electrical properties of PP/MWCNT nanocomposites. Addition of organo-clay (MWCNT/OC ratio was 1/1) reduced the percolation threshold of PP/MWCNT nanocomposites from ?_c = 0.95 vol.% to ?_c = 0.68 vol.% of carbon nanotubes, while the level of conductivity became 2–4 orders of magnitude higher. The DSC and DMA analyses have shown that the influence of organo-clay on the thermal and mechanical properties of material was not significant in composites with both fillers as compared to PP/OC. Such an effect can be caused by stronger interaction of OC with carbon nanotubes than with polymer matrix.     

Surface modification of MWCNTs with glucose and their utilization for the production of environmentally friendly nanocomposites using biodegradable poly(amide‐imide) based on N‐trimellitylimido‐S‐valine matrix

In the present investigation, the preparation, characterization, and surface morphology of poly(amide‐imide) (PAI)/multi‐walled carbon nanotubes (MWCNTs) bionanocomposites (BNCs) were the main goals of the study. At first, an optically active PAI based on S‐valine as a biodegradable segment was synthesized. Then, carboxyl‐modified MWCNTs were functionalized with glucose (f‐MWCNT) as a biological active molecule in a green method to achieve a fine dispersion of f‐MWCNT bundles in the PAI matrix. The existence of S‐valine in the PAI matrix and functionalized MWCNT with glucose resulted in a series of potentially biodegradable nanocomposites. The obtained BNCs were characterized by various techniques. Field emission scanning and transmission electron microscopy micrographs of the composites showed a fine dispersion of f‐MWCNTs in the polymer matrix because of hydrogen bonding and π–π stacking interaction between f‐MWCNTs and polymer functional groups and aromatic moieties. Adding f‐MWCNTs into polymer matrix significantly improved the thermal stability of BNCs because of the increased interfacial interaction between the PAI matrix and f‐MWCNTs and also good dispersion of f‐MWCNT in the polymer matrix. Copyright © 2015 John Wiley & Sons, Ltd.     

Influence of talc with different particle sizes in melt‐mixed LLDPE/MWCNT composites

Linear low‐density polyethylene (LLDPE) was melt‐mixed with multiwalled carbon nanotubes (MWCNTs) and varying amounts of three different kinds of talc (phyllo silicate), each with a different particle size distribution, to examine the effect of these filler combinations with regards to the electrical percolation behavior. The state of the filler dispersion was assessed using transmission light microscopy and electron microscopy. The use of talc as a second filler during the melt mixing of LLDPE/MWCNT composites resulted in an improvement in the dispersion of the MWCNTs and a decrease of the electrical percolation threshold. Talc with lower particle sizes showed a more pronounced effect than talc with larger particle sizes. However, the improvement in dispersion was not reflected in the mechanical properties. Modulus and stress values increase with both, MWCNT and talc addition, but not in a synergistic manner. The crystallization behavior of the composites was studied by differential scanning calorimetry to determine its potential influence on the electrical percolation threshold. It was found that the crystallinity of the matrix increased slightly with the addition of talc but no further increments were observed with the incorporation of the MWCNTs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1680–1691     

Binary Au/MWCNT and Ternary Au/ZnO/MWCNT Nanocomposites: Synthesis,Characterisation and Catalytic Performance

Gold nanoparticles of 10–24 and 5–8 nm in size were obtained by chemical citrate reduction and UV photoreduction, respectively, on acid‐treated multiwalled carbon nanotubes (MWCNTs) and on ZnO/MWCNT composites. The shape and size of the deposited Au nanoparticles were found to be dependent upon the synthetic method used. Single‐crystalline, hexagonal gold particles were produced in the case of UV photoreduction on ZnO/MWCNT, whereas spherical Au particles were deposited on MWCNT when the chemical citrate reduction method was used. In the UV photoreduction route, n‐doped ZnO serves as the e^? donor, whereas the solvent is the hole trap. All materials were fully characterised by UV/Vis spectroscopy, scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, Raman spectroscopy and BET surface analysis. The catalytic activity of the composites was studied for the selective hydrogenation of α,β‐unsaturated carbonyl compound 3,7‐dimethyl‐2,6‐octadienal (citral). The Au/ZnO/MWCNT composite favours the formation of unsaturated alcohols (selectivity=50 % at a citral conversion of 20 %) due to the presence of single‐crystalline, hexagonal gold particles, whereas saturated aldehyde formation is favoured in the case of the Au/MWCNT nanocomposite that contains spherical gold particles.     

Anisotropic studies of multi-wall carbon nanotube (MWCNT)-filled natural rubber (NR) and nitrile rubber (NBR) blends

50/50 NR/NBR blends with various MWCNT loadings were prepared by mixing with MWCNT/NR masterbatches on a two-roll mill and sheeted off at the smallest nip gap. Then, the effect of milling direction, machine direction (MD) and transverse direction (TD), on the mechanical and electrical properties of the blends was elucidated. Dichroic ratio and SEM results confirmed that most of the MWCNTs were aligned along MD when MWCNT was less than 4 phr, and the number of agglomerates increased when MWCNT was more than 4 phr. Additionally, anisotropic properties were clearly observed when 4 phr MWCNT was loaded. At 4 phr MWCNT, 100% modulus and tensile strength in the MD were about 1.5 and 1.3 times higher than those in the TD, respectively. Moreover, electrical conductivity in the MD was superior to that in the TD by about 3 orders of magnitude. Results from dynamic mechanical tests also showed that the maximum tan δ in the MD sample was lower than that in the corresponding TD sample. In addition, the storage modulus at 30 °C for the MD sample containing 4 phr MWCNT was 1.15 higher than that of the corresponding TD sample. This stronger reinforcement efficiency resulted from the combination of the greater alignment and dispersion of most MWCNTs in the MD sample.     

Improvement in Heat Transfer of a Two-Phased Closed Thermosyphon Using Silver-Decorated MWCNT/Water

Hereby, a comparative study of thermal and thermodynamic properties of nanofluids based on multiwalled carbon nanotubes (MWCNTs) and water is described. The first nanofluid includes pristine MWCNT while the second nanofluid prepared by MWCNT decorated with silver. To achieve the covalent functionalization, morphology of MWCNT-Ag was studied by transmission electron microscopy. Subsequently, the value of the entropy generation and thermal performance of nanofluids (MWCNT/water and MWCNT-Ag/water) were inspected in a two-phased closed thermosyphon (TPCT). The results suggested as the concentration and input power increased, the thermal resistance decreased. Also in different concentrations, the thermal efficiency of nanofluids obeyed the sequence: MWCNT-Ag (1 wt%) > MWCNT-Ag (0.5 wt%) > MWCNT (1 wt%) > MWCNT (0.5 wt%) > water. A variation of the vacuum pressure was also studied in the synthesized nanofluids as compared with pure water. The results were shown a lower pressure drop of MWCNT-Ag/water than MWCNT/water and the water. Also it was found that the higher thermal performance is produced using higher extent of covalent functional groups (with higher thermal conductivity). MWCNT-Ag/water can be an appropriate substitution for the water in the thermal equipment due to the intensive thermal efficiency and/or low thermal resistance compared with pure water.      

碳纳米管改性聚苯硫醚熔纺纤维的结构与性能研究

将多壁碳纳米管(MWCNTs)和聚苯硫醚(PPS)经过熔融挤出后制备成复合材料切片,并采用熔融纺丝法制得碳纳米管改性聚苯硫醚复合纤维.采用扫描电镜(SEM)、拉曼光谱、示差扫描量热分析(DSC)、动态机械分析(DMA)以及力学性能测试等表征手段研究了复合纤维中碳管的分散状态,与基体的界面作用,复合纤维的结晶性能以及力学性能,从而探讨了聚苯硫醚/碳纳米管复合纤维体系的微观结构与宏观性能之间的关系.研究表明,聚苯硫醚分子结构与碳纳米管之间具有的π-π共轭作用使碳管较为均匀的分散在基体中,界面结合较为紧密.同时熔融纺丝过程中的拉伸作用使碳管进一步解缠并使碳管沿纤维拉伸方向取向.另一方面,拉曼光谱显示拉伸作用有效地增强了界面作用,有利于外界应力的传递.碳管的良好分散以及强的界面作用使复合纤维力学性能得到大幅度的提高,当碳管含量达到5 wt%时,复合纤维的模量有了明显的提高,拉伸强度较纯PPS纤维提高了近220%.     

Synthesis and studies of thermal,mechanical and electrical properties of MWCNT–cyclodextrin as a nanoparticle in polyamide matrix based on 2,2‐Bis[4‐(4‐aminophenoxy)phenyl] propane

In the present research, polyamide (PA) ( 6 ) was synthesized by the polycondensation reaction of 2,2‐Bis[4‐(4‐aminophenoxy)phenyl] propane as a diamine ( 4 ) with adipic acid ( 5 ) in the optimized condition. The resulting PA was characterized using Fourier transform infrared spectroscopy, Proton Nuclear Magnetic Resonance (¹H NMR) spectroscopy, inherent viscosity (η_inh), X‐ray diffraction, and solubility tests. Also, the thermal property of the new PA ( 6 ) was investigated by using Thermogravimetric analysis. To apply multiwall carbon nanotube (MWCNT) as an effective reinforcement in polymer composites, it is essential to have appropriate proper dispersion, interfacial adhesion between the MWCNT and polymer matrix, and increasing solubility. With this end particularly, functionalized MWCNTs were combined with a soluble molecule, and a series of modified MWCNT with cyclodextrin (Cy) known as PA/MWCNT‐Cy composite film (2, 5, and 8 wt%) were prepared by a solution intercalation technique. Field emission scanning electron microscopy images showed that MWCNT‐Cy was well dispersed in the PA matrix. Thermogravimetric analysis indicated an increase in thermal stability of nanocomposites as compared with the pristine PA. Anisotropic structure of the synthesized films and dispersed MWCNT‐Cy in the films approved by use of X‐ray diffraction and field emission scanning electron microscopy. The resultant PA/MWCNT‐Cy composite films were electrically conductive, which is favorable for many practical uses. Measurements of mechanical properties of these composite films showed high strength in 8% MWCNT‐Cy content. Also, results showed increases in Young's modulus and tensile strength. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation and morphological,electrical, and mechanical properties of polyimide‐grafted MWCNT/polyimide composite

Precursor of polyimide, polyamic acid has been prepared sucessfully. Acid‐modified carbon nanotube (MWCNT) was grafted with soluble polyimide then was added to the polyamic acid and heated to 300 °C to form polyimide/carbon nanotube composite via imidation. Morphology, mechanical properties and electrical resistivity of the MWCNT/polyimide composites have been studied. Transmission electron microscope microphotographs show that the diameter of soluble polyimide‐grafted MWCNT was increased from 30–60 nm to 200 nm, that is a thickness of 70–85 nm of the soluble polyimide was grafted on the MWCNT surface. PI‐g‐MWCNT was well dispersed in the polymer matrix. Percolation threshold of MWCNT/polyimide composites has been investigated. PI‐g‐MWCNT/PI composites exhibit lower electrical resistivity than that of the acid‐modified MWCNT/PI composites. The surface resistivity of 5.0 phr MWCNT/polyimide composites was 2.82 × 10⁸ Ω/cm² (PI‐g‐MWCNT) and 2.53 × 10⁹ Ω/cm² (acid‐modified MWCNT). The volume resistivity of 5.0 phr MWCNT/polyimide composites was 8.77 × 10⁶ Ω cm (PI‐g‐MWCNT) and 1.33 × 10¹³ Ω cm (acid‐modified MWCNT).Tensile strength and Young's modulus increased significantly with the increase of MWCNT content. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3349–3358, 2007     

Influence of modification of MWCNTs on the structure and performance of MWCNT‐Poly(MMA‐AM) hybrid membranes

Hybrid membranes containing multi‐walled carbon nanotubes (MWCNTs) were initially prepared to separate benzene/cyclohexane mixtures. Subsequently, MWCNT surfaces were chemically modified using two methods to change the surface polarity of the MWCNTs and improve the distribution thereof in Poly(methylmethacrylate) (PMMA). This change consequently enhanced the separation performance of hybrid membranes with MWCNTs. Raman spectroscopy was used to characterize the structure of the pristine MWCNTs and the modified MWCNTs. The morphology and distribution of the MWCNTs in PMMA were investigated by transmission electron microscopy. The results showed that the addition of MWCNTs clearly improved the separation performance of the hybrid membranes. Surface modification introduced polar groups onto the MWCNT surface, which significantly improved the distribution of MWCNTs in the PMMA membranes and the performance of hybrid membranes. MWCNTs with higher surface polarity also increased the amount of MWCNTs distributed homogeneously in PMMA. Aminated MWCNTs (MWCNT‐NH₂) showed the highest surface polarity. Thus, the content of MWCNT‐NH₂ well distributed in PMMA was the highest among the three types of MWCNTs. The highest separation factor for the hybrid membranes with 1.0 wt% MWCNT‐NH₂ was about seven times that of membranes containing pristine MWCNTs. Copyright © 2013 John Wiley & Sons, Ltd.