Nylon 610/functionalized multiwalled carbon nanotube composite prepared from in‐situ interfacial polymerization

Pristine multiwalled carbon nanotubes (P‐MWNTs) were functionalized with 4‐chlorobenzoic acid via “direct” Friedel‐Crafts acylation in polyphosphoric acid (PPA)/phosphorous pentoxide (P₂O₅) medium. The resultant 4‐chlorobenzoyl‐functionalized MWNTs (F‐MWNTs) were soluble in chlorinated solvents such as dichloromethane, chloroform, and carbon tetrachloride. A large scale of nylon 610/F‐MWNT composite could be conveniently prepared by in situ interfacial polymerization of 1, 6‐hexamethylenediamine (HMDA) in an aqueous phase, and sebacoyl chloride with F‐MWNTs in an organic phase. Similarly, nylon 610/P‐MWNT composite was also prepared for comparison. The state of F‐MWNTs dispersion in nylon 610 matrix was distinctively better than that of P‐MWNTs, which could be clearly discerned by both naked eye and scanning electron microcopy (SEM). As a result, the tensile strength of nylon 610/F‐MWNT composite was 4.9‐fold higher than that of nylon 610/P‐MWNT composite. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6041–6050, 2008     

Chemically grafting carbon nanotubes onto carbon fibers for enhancing interfacial strength in carbon fiber/HDPE composites

We propose a novel method to uniformly graft high‐density carbon nanotubes (CNTs) onto carbon fiber (CF) by using coupling agents. Coupling agents can supply much more active groups, which is beneficial for grafting high‐density CNTs onto CF surface. After CNT grafting treatment, there are still substantial amounts of reactive groups, which can further react with various types of molecules to meet different requirements. To create chemical bonding between CF and high‐density polyethylene, CF‐CNT was further grafted get reinforcement. The interfacial adhesion of the resulting composites showed a dramatic improvement.     

Conjugated polymer covalently modified multiwalled carbon nanotubes for optical limiting

A new soluble multiwalled carbon nanotubes (MWNTs) covalently functionalized with conjugated polymer PCBF, in which the wt % of MWNTs is approximately calculated as 7.3%, and the average thickness of PCBF covalently grafted onto MWNTs is 10.4 nm, was synthesized by an amidation reaction. In contrast to the starting polymer PCBF‐NH₂, grafting of PCBF onto MWNTs led to a 0.3 eV red‐shift of the N1s XPS peak at 399.7 eV assigning to N in the unreacted NH₂moieties in the resulting copolymer structure and an appearance of new peak at 402 eV corresponding to N bound to the carbonyl C (i.e., NH? C?O). Unlike PCBF‐NH₂, which only displayed a weak optical limiting response at 532 nm, Z‐scan for MWNT‐PCBF exhibited a much broader reduction in transmission and a scattering accompanying on the focus of the lens at both 532 and 1064 nm, indicating a prominent broadband optical limiting response. The thermally induced nonlinear scattering is responsible for the optical limiting. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Effects of carbon nanotubes on polymer physics

A single carbon nanotube has many similarities with an individual polymer chain including the fact that the end‐to‐end length of both are often about the same and the diameter of the chain is about the same (for single‐walled nanotubes) or only ～10 to 20 times larger (for multiwalled nanotubes). The combination of the solid surface and the similarity of the two materials means that polymer physics are altered in manners not seen with any other type of commonly used filler. The purpose of this review is to update a chapter that appears in a recent tome by Grady (2011) and describe how polymer physics is altered in composites that contain carbon nanotubes. Subjects that will be discussed include chain configuration, glass transition, polymer diffusion, unit cells and crystalline superstructure (lamellae, spherulites and shish‐kebabs), and crystallization kinetics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Improved interfacial properties of PI composites through graphene oxide and carbon nanotubes on carbon fiber surface

Carbon nanotubes (CNTs) have been identified as excellent nanoreinforcements for carbon fiber (CF)–reinforced polymers regarding a wide range of engineering applications. The outstanding properties of CNTs, such as their large surface area, high mechanical strength, and low manufacturing cost bring them to be distinguished nanoreinforcements for carbon fiber–reinforced polymers to form multifunctional and multiscale composites. Electrophoretic deposition of graphene oxide for CNTs onto the CF surface was conducted. The presence of graphene oxide–CNTs may effectively increase both the roughness and wettability of the CF surface, resulting in an improvement to the interfacial bonding strength between the CF and the polyimide (PI).     

Improved microhardness and microtribological properties of bismaleimide nanocomposites obtained by enhancing interfacial interaction through carbon nanotube functionalization

Through the functionalization of multiwalled carbon nanotubes (MWCNTs) by 0,0′‐diallylbisphenol A (DBA), the interface situation between MWCNTs and bismaleimide (BMI) was improved, as detected by scanning electron microscope (SEM) and dynamic mechanical analysis (DMA). The improved interface situation was considered to be the main reason for the huge increased microhardness value and greatly improved the microtribological property of MWCNTs/BMI composites. Besides, the wear mechanism for the composite was also believed to be related to the interfacial situation. The rough wavelike worn surface of pure BMI resin is attributed to its poor load capacity. The smoother waterfall‐shape worn surface of MWCNTs/BMI is related to the interface formed by the addition of MWCNTs while the ultrasmooth worn surface of DBA modified MWCNTs/BMI is due to the greatly improved interfacial interaction of the composite. Copyright © 2008 John Wiley & Sons, Ltd.     

Rheology of polycarbonate reinforcedwith functionalized and unfunctionalized single-walled carbon nanotubes

Nanocomposites of polycarbonate (PC) containing low concentrations of pristine and COOH and OH functionalized single-walled carbon nanotubes (SWNTs, COOH-SWNTs and OH-SWNTs) were prepared by melt-mixing and analyzed using rheology and scanning electron microscopy (SEM). The steady state and linear viscoelastic behavior of each nanocomposite material is presented and compared to that of the neat PC. SEM analysis revealed that samples containing functionalized SWNTs were more dispersible than samples containing the pristine SWNTs.     

多壁碳纳米管表面L-组氨酸手性印迹聚合材料的制备及性能表征

通过酰胺化反应在多壁碳纳米管（MWNTs）表面接枝双键,以L-组氨酸（L-His）为模板,甲基丙烯酸（MAA）为功能单体,乙二醇二甲基丙烯酸酯（EGDMA）为交联剂,偶氮二异丁腈（AIBN）为引发剂,利用表面印迹技术,在MWNTs表面制备印迹聚合物（MWNTs-MIPs）．采用红外光谱,扫描电子显微镜和热重分析表征印迹聚合物的性质,结果表明MWNTs表面成功接枝了一层稳定的、厚度为35～40nm具有识别能力的印迹聚合材料．结合高效液相色谱技术,通过填充色谱柱在线色谱分析,探讨不同pH值的流动相下该印迹材料对L-His的分离行为,结果表明MWNTs—MIPs色谱柱在流动相pH=7．0时分离效果最好,能够选择性地识别L-His和D-His,分离度R为1．78,选择因子α为1．28．     

Enhanced dispersion of nanotubes in organic solvents by donor–acceptor interaction between functionalized poly(phenylacetylene) chains and carbon nanotube walls

Phenylacetylene derivatives containing carbazole ( 1 ) and fluorene ( 2 ) moieties were polymerized by [Rh(nbd)Cl]₂ into corresponding polymers P 1 and P 2 of high molecular weights (M_w ～ 150 × 10³–465 × 10³) in high yields (up to 98%). The polymers were characterized by NMR, IR, UV, PL, and CV techniques. Hybrids of the polymers with multiwalled carbon nanotubes (MWNTs) were prepared by simply mixing the two components in common organic solvents such as dichloromethane. The solvating power of the polymer carrying the electron‐donating carbazolyl pendant (P 1 ) is stronger than that of its counterpart carrying fluorenyl pendant (P 2 ), due to the stronger donor–acceptor (D–A) interaction between the P 1 chains and the MWNT walls. This work clearly manifests that D–A effect plays an important role in the polymer‐aided MWNT dispersion in organic solvents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4995–5005, 2009     

Noncovalent modification of carbon nanotubes by conjugated polymer: A theoretical study

The energetic and optical properties of (n, n) carbon nanotubes (CNTs) for n = 3–11 noncovalently modified with poly(phenylenethynylene) (PPE) were studied using a density‐functional tight‐binding method. The binding energies between the PPE and (n, n) CNTs were found increasing with the diameter increase for n ≤ 9 and then decreasing due to steric hindrance effect. It was verified that the binding is due to π–π interaction and van der Waals attraction, with very small charge transfers involved. Significant blue shifts in the absorption and fluorescent spectra of the PPE upon interacting with the CNTs were revealed in the calculation, which are responsible to the optical “quenching” observed in experiment. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Crystallization improvement of poly(L‐lactide) induced by functionalized multiwalled carbon nanotubes

In the present work, the crystalline structures and the melting behaviors of poly(L ‐lactide) (PLLA) obtained after being annealed at different conditions have been investigated through differential scanning calorimetry and wide‐angle X‐ray diffraction, respectively. To improve the crystallization of PLLA, functionalized multiwalled carbon nanotubes (f‐MWCNTs) are introduced into PLLA. Our results show that by prolonging the annealing duration or enhancing the annealing temperature, the degree of crystallinity of PLLA gradually increases. Very important, the addition of f‐MWCNTs promotes the cold‐crystallization of PLLA dramatically even at relatively lower annealing temperature or in shorter annealing duration. Further results show that, whether in neat PLLA or in PLLA/f‐MWCNTs nanocomposite, only α form crystal forms during the annealing process. The glass transition temperature shifts to high temperatures because of the increase of crystallinity. F‐MWCNTs exhibit great heterogeneous nucleation effect for PLLA crystallization through enhancing the nucleation density, leading to homogeneous and tiny spherulites formation in a very short time. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 326–339, 2009     

Sensitive determination of hydrazine using poly(phenolphthalein), Au nanoparticles and multiwalled carbon nanotubes modified glassy carbon electrode

This study reports a detailed analysis of an electrode material containing poly(phenolphthalein), carbon nanotubes and gold nanoparticles which shows superior catalytic effect towards to hydrazine oxidation in Britton–Robinson buffer (pH 10.0). Glassy carbon electrode was modified by electropolymerization of phenolphthalein (PP) monomer (poly(PP)/GCE) and the multiwalled carbon nanotubes (MWCNTs) was dropped on the surface. This modified surface was electrodeposited with gold nanoparticles (AuNPs/CNT/poly(PP)/GCE). The fabricated electrode was analysed the determination of hydrazine using cyclic voltammetry, linear sweep voltammetry and amperometry. The peak potential of hydrazine oxidation on bare GCE, poly(PP)/GCE, CNT/GCE, CNT/poly(PP)/GCE, and AuNPs/CNT/poly(PP)/GCE were observed at 596 mV, 342 mV, 320 mV, 313 mV, and 27 mV, respectively. A shift in the overpotential to more negative direction and an enhancement in the peak current indicated that the AuNPs/CNT/poly(PP)/GC electrode presented an efficient electrocatalytic activity toward oxidation of hydrazine. Modified electrodes were characterized with High-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Amperometric current responses in the low hydrazine concentration range of 0.25–13 µM at the AuNPs/CNT/poly(PP)/GCE. The limit of detection (LOD) value was obtained to be 0.083 µM. A modified electrode was applied to naturel samples for hydrazine determination.     

Surface modification of carbon fiber for improving the interfacial adhesion between carbon fiber and polymer matrix

In this study, the reinforcing mechanism of amine functionalized on carbon fibers (CFs) has been precisely discussed, and the differences between aliphatic and aromatic compounds have been illustrated. Polyacrylonitrile‐based CFs were functionalized with ethylenediamine, 4,4‐diaminodiphenyl sulphone, and p‐aminobenzoic acid (PAB), and CF‐reinforced epoxy composites were prepared. The structural and surface characteristics of the functionalized CFs were investigated using X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT‐IR), and scanning electron microscopy (SEM). Mechanical properties in terms of tensile and flexural strengths and moduli were studied. The FT‐IR results confirm the success in bonding amines on the CF surface. After treatment of CFs, the oxygen and nitrogen contents as well as the N/C ratio showed an increase. XPS results provided evidence of the chemical reaction during functionalization, rather than being physically coated on the CF surface. Chemical modification of CF with diamines led to considerable enhancement in compatibility of CF filaments and epoxy resin, and remarkable improvements were seen in both tensile and flexural properties of the reinforced composites. SEM micrographs also confirmed the improvement of interface adhesion between the modified CFs and epoxy matrix. Finally, it can be concluded that PAB is a promising candidate to functionalize CF in order to improve interfacial properties of CF/epoxy composites. Copyright © 2015 John Wiley & Sons, Ltd.     

Tuning retention and selectivity in reversed-phase liquid chromatography by using functionalized multi-walled carbon nanotubes

Aim of this work was to explore the possibility of retention and selectivity tuning in reversed-phase liquid chromatography by means of chemically modified multi-walled carbon nanotubes (MWCNTs). These were synthesized by derivatizing pristine MWCNTs with amino-terminated alkyl chains containing polar embedded groups. A novel hybrid material based on functionalized MWCNTs (MWCNTs-R-NH₂) was prepared, characterized and tested. The idea was to design a mixed-mode separation medium basing its sorption properties on the peculiar characteristics of MWCNTs combined with the chemical interactions provided by the functional chains introduced on the nanotube skeleton. MWCNTs-R-NH₂ were easily grafted to silica microspheres by gamma radiation (using a ⁶⁰Co source) in the presence of polybutadiene as the linking agent. The composite was characterized by scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) analysis in terms of structural morphology, surface area and porosity. The MWCNTs-R-NH₂ sorbent was tested as stationary phase. The reversed-phase behaviour was first proved by analysis of alkylbenzenes, while the key role of CNT derivatization in addressing the selectivity/affinity towards the solutes was evidenced by testing three classes of analytes, viz. barbiturates, steroid hormones and alkaloids. These compounds, with different molecular structure and polarity, were here analysed for the first time on CNT-based LC stationary phases. The behaviour of the novel sorbent was compared in terms of retention capability and resolution with that observed using unmodified MWCNTs, pointing out the mixed-mode characteristics of the MWCNTs-R-NH₂ material. The same test mixtures were analysed also on a conventional mono-modal separation sorbent (C18) to highlight the particular behaviour of the (derivatized)MWCNTs-based stationary phases. The novel material showed better performance in separation of polar compounds, i.e. barbiturates and alkaloids, than the unmodified MWCNTs and than the C18 column. Results showed that MWCNT functionalization is powerful to modulate retention/selectivity in reversed-phase liquid chromatography.     

Influence of carbon on the interfacial contact angle between alumina and liquid aluminum

The wetting of alumina by pure liquid aluminum was investigated over the temperature range 900–1300°C by the sessile drop method under a dynamic vacuum of 10^?4–10^?5 Pa. When the substrate is carbon coated, the terminal contact angle is reduced to 40° at 1300°C for times longer than 4500 s. In the absence of carbon, the final angle is 82° for the same conditions. Reactive wetting is suggested by the observation of undercutting of the substrate and ridge formation at the leading edge of the liquid aluminum in all carbon‐coated samples. Based on energy considerations, the following is among the thermodynamically favorable reactions: 4Al + 3C → Al₄C₃. Possible mechanisms for the observed carbon‐enhanced wettability in the system are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Nanocomposite prepared from in situ grafting of polypyrrole to aminobenzoyl‐functionalized multiwalled carbon nanotube and its electrochemical properties

We reported the functionalization of multiwalled carbon nanotube (MWCNT) with 4‐aminobenzoic acid by a “direct” Friedel–Crafts acylation reaction in a mild polyphosphoric acid (PPA)/phosphorous pentoxide (P₂O₅) medium. The resulting 4‐aminobenzoyl‐functionalized MWCNT (AF‐MWCNT) was used as a platform for the grafting of polypyrrole (PPy) in ammonium persulfate (APS)/aqueous hydrochloric acid solution to produce PPy‐grafted MWCNT (PPy‐g‐MWCNT) composite. After dedoping with alkaline treatment, PPy‐g‐MWCNT displayed 20 times higher electrical conductivity than that of PPy. The current density and cycle stability of PPy‐g‐MWCNT composite were also remarkably improved compared with those of PPy homopolymer, suggesting that an efficient electron transfer between PPy and MWCNT was possible through covalent links. In addition, PPy‐g‐MWCNT displayed high electrocatalytic activity for oxygen reduction reaction (ORR). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of carbon nanotubes and their dispersion on thermal curing of polyimide precursors

The process of thermal imidization reaction is significant for temperature and time control in the polyimide industry. Here, we report the effect of carbon nanotubes and their states of dispersion on the thermal imidization of the precursor films of polyimide (poly(amic acid)) for the first time. The curing process was followed by measuring Fourier transform-infrared (FT-IR) spectra, fluorescence spectra, thermogravimetric-differential scanning calorimeter (TG-DSC) properties and the refractive indices of films. It was found that by evenly dispersing 1 wt% of carbon nanotubes assisted by a dispersant in the poly(amic acid),the full imidization temperature of the polyimide can be reduced from 300 °C to 250 °C. Different states of distribution of CNTs were observed by light microscopy and scanning electron microscopy, and proved that a better dispersion of carbon nanotubes dramatically enhanced the speed of imidization. Moreover, the DSC results showed that lower decomposition temperature of poly(amic acid) could be obtained with more uniform distribution of carbon nanotubes, which means the process of cyclodehydration of the poly(amic acid) was accelerated.     

“Click” coupling between alkyne‐decorated multiwalled carbon nanotubes and reactive PDMA‐PNIPAM micelles

Covalent functionalization of alkyne‐decorated multiwalled carbon nanotubes (MWNTs) with a well‐defined, azide‐derivatized, thermoresponsive diblock copolymer, poly(N,N‐dimethylacrylamide)‐poly(N‐isopropylacrylamide) (PDMA‐PNIPAM) was accomplished by the Cu(I)‐catalyzed [3 + 2] Huisgen cycloaddition. It was found that this reaction could simultaneously increase the molecular size and bonding density of grafted polymers when PDMA‐PNIPAM micelles were employed in the coupling system. On the other hand, attachment of molecularly dissolved unimers of high‐molecular weight onto the nanotube resulted in low‐graft density. The block copolymer bearing azide groups at the PDMA end was prepared by reversible addition–fragmentation transfer polymerization, which formed micelles with a diameter of ～40 nm at temperatures above its critical micelle temperature. Scanning electron microscopy was utilized to demonstrate that the coupling reaction was successfully carried out between copolymer micelles and alkyne‐bearing MWNTs. FTIR spectroscopy was utilized to follow the introduction and consumption of alkyne groups on the MWNTs. Thermogravimetric analysis indicated that the functionalized MWNTs consisted of about 45% polymer. Transmission electron microscopy was utilized to image polymer‐functionalized MWNTs, showing relatively uniform polymer coatings present on the surface of nanotubes. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7187–7199, 2008     

Chitosan/polyvinyl alcohol/amino functionalized multiwalled carbon nanotube pervaporation membranes: Synthesis,characterization, and performance

In the present study, novel biodegradable nanocomposite membranes were prepared by adding the amino functionalized multiwalled carbon nanotube (NH₂‐MWCNT) to the chitosan/polyvinyl alcohol blend polymers, and the obtained membranes were used for dehydration of isopropyl alcohol through pervaporation process. For this purpose, the membranes were prepared with chitosan/polyvinyl alcohol ratio of 4:1 on the basis of “solution casting” method and then crosslinked using glutaraldehyde, after addition of different amounts of NH₂‐MWCNT. The prepared membranes were characterized using scanning electron microscopy, contact angle, mechanical strength, degree of swelling (DS), and biodegradability. Also, the ability of the prepared membranes in dehydration of isopropyl alcohol was determined using pervaporation experiments. Results indicated that contact angle, mechanical resistance, separation factor (α), and pervaporation separation index were increased with the addition of NH₂‐MWCNT up to 10 wt% (relative to the total amount of polymer) and then decreased in the higher presence of nanotubes (15 wt%). Furthermore, the DS and permeate flux were first decreased and then increased for the same mentioned amounts of additive. In this study, optimized membrane was obtained by the addition of 10 wt% NH₂‐MWCNT. This membrane showed the maximum α (99.5), pervaporation separation index parameter (78.29 kg m⁻² h⁻¹), biodegradability, and mechanical stability as well as minimum DS.     

Polymer brushes on multiwalled carbon nanotubes by activators regenerated by electron transfer for atom transfer radical polymerization

The synthesis and characterization of multiwalled carbon nanotube (MWCNT) polymer brushes produced by activators regenerated by electron transfer (ARGET) in atom‐transfer radical polymerization (ATRP) was discussed. The polymer brushes were synthesized by esterification of the MWCNT carboxylic acid groups with hydroxyethyl‐2‐bromoisobutyrate and subsequently used in ARGET ATRP. This created a well defined living polymer brush carbon nanotube of comparatively low polydispersity and a polymer layer 10 nm thick. As, ARGET ATRP uses only minute concentrations of copper (II) catalyst, and is less sensitive to air compared to other living polymerization techniques, this process is a more industry‐compatible route for the commercialization of such materials. The structural and chemical properties were explored by a range of techniques including high resolution transmission electron microscopy, gel permeation chromatography, elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. In addition, the polymer brush nanotubes were explored for their potential use in films and as fillers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011