Grafting polyamide 6 onto multi‐walled carbon nanotubes using microwave irradiation

Chemical reactions under microwave irradiation can be very efficient, with a significant shortening of reaction time. Few studies have reported the use of microwaves to functionalize carbon nanotubes. In the work reported, a new method of formulating functionalized multi‐walled carbon nanotubes (MWNTs) was developed by covalent grafting of polyamide 6 (PA6) chains onto the carbon nanotubes assisted by microwave irradiation. PA6 chains were grafted onto acidified MWNTs through condensation reaction between the carboxylic groups of the MWNTs and the terminal amine groups of PA6 using microwave radiation heating. The functionalized carbon nanotubes (MWNT‐g‐PA6) were characterized systematically using infrared and Raman spectroscopy, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). TEM showed that the surface of the MWNTs was covered with a layer of PA6. TGA results indicated that the MWNT‐g‐PA6 contained about 47 wt% of polymer. A novel, convenient and efficient functionalization approach is reported, involving covalently grafting PA6 chains onto MWNTs assisted by microwave irradiation. Copyright © 2010 Society of Chemical Industry     

The synthesis of covalent bonded single‐walled carbon nanotube/polyvinylimidazole composites by in situ polymerization and their physical characterization

Single‐walled carbon nanotube (SWCNT) polyvinylimidazole (PVI) composites have been prepared by in situ emulsion polymerization. Dispersion of raw SWCNTs in the PVI matrix was improved by surface modification of the SWCNTs using nitric acid treatment and air oxidation. The carbonyl‐terminated SWCNTs were covalently bonded to PVI by in situ polymerization and the SWCNT/PVI composite was thus obtained. The morphological and structural characterizations of the surface‐functionalized SWCNTs and SWCNT/PVI composites were carried out by Fourier transform infrared spectroscopy, X‐ray diffraction, conductivity measurements, scanning, and transmission electron microscopy. Thermograms of the materials were determined by the differential scanning calorimetry technique. The characterization results indicate that PVI was covalently bonded to SWCNTs and a new material was then obtained. The functionalized SWCNTs showed homogenous dispersion in the composites, whereas purified SWCNT resulted in poor dispersion and nanotube agglomeration. SWCNT/PVI composites exhibited chemical stability enhancement in many common solvents. I–V curves of the samples exhibit an ohmic character. Conductivity values for pure SWCNTs, pure PVI and SWCNT/PVI composite were measured to be 3.47, 2.11 × 10⁻⁹, and 2.3 × 10⁻³ S/m, respectively. Because of resonance, a large dielectric constant is obtained for SWCNT/PVI composite, which is not observed for ordinary materials. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

p-Hexafluoroisopropanol phenyl covalently functionalized single-walled carbon nanotubes for detection of nerve agents

Novel p-hexafluoroisopropanol phenyl (HFIPPH) covalently functionalized single-walled carbon nanotubes (SWCNTs) have been prepared through in situ diazonium reaction between SWCNTs and p-hexafluoroisopropanol aniline; moreover, the hybridized material can be characterized by ultraviolet vision near infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, X-ray photoelectron spectrometry, field-emission scanning electron microscopy and high resolution transmission electron microscopy. The results reveal that the one-dimensional electronic structures of the functionalized tubes could be basically maintained without damaging their electronic properties. Considered that strong hydrogen-bonding can be formed between hexafluoroisopropanol groups and dimethyl methylphosphonate (DMMP) (simulant of nerve agent sarin), the SWCNT-HFIPPH sensing devices have been fabricated and employed to detect DMMP. Excellent sensitivity and selectivity of the hybridized SWCNT-HFIPPH devices suggest that it has great capability of detecting explosives and chemical warfare agents.     

Improving the thermal and mechanical properties of poly(vinyl butyral) through the incorporation of acid‐treated single‐walled carbon nanotubes

In this study, to investigate the effect of functionalized carbon nanotubes on the thermal and mechanical properties of the poly(vinyl butyral) (PVB) resin, PVB/functionalized single‐walled carbon nanotube (f‐SWCNT) composites were fabricated by a solution casting method. The functionalized nanotubes were prepared by acid treatment. The formation of oxygen‐containing functional groups on the surface of the nanotubes was confirmed by Fourier transform infrared spectroscopy, energy‐dispersive X‐ray spectroscopy, and scanning electron microscopy (SEM) measurements. SEM analysis also showed that the nanotubes were dispersed well in the PVB matrix. The thermal stability of the composites were investigated with thermogravimetric analysis, and the results show better stability for PVB in the presence of a very low content of the f‐SWCNTs. The prepared composites exhibited a significant increase in the temperature of degradation at 50 wt % loss and also in the onset temperature and decomposition temperature at the maximum rate of weight loss of butyral degradation. A significant enhancement in the mechanical properties was also achieved for these prepared composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40481.     

Grafting of an aminated poly(phenylene sulphide) derivative to functionalized single-walled carbon nanotubes

An aminated poly(phenylene sulphide) derivative (PPS-NH₂) has been covalently anchored to the surface of epoxy and acid-functionalized single-walled carbon nanotubes (SWCNTs). The characterisation through Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis and Kaiser test corroborated the success of the grafting reactions, and allowed the identification and quantification of the covalent moieties. Scanning and transmission electron microscopy indicated an increase in the bundle diameter of the SWCNTs upon anchoring of the polymer chains. The results showed that the storage modulus, glass transition temperature and electrical conductivity of the polymer were exceptionally enhanced by the attachment to the SWCNTs. In contrast, the crystallization and melting temperature, degree of crystallinity and crystal size considerably decreased, as revealed by differential scanning calorimetry and X-ray diffraction experiments, due to the inactive nucleating role of these SWCNTs and the intense restrictions on chain mobility imposed by the SWCNT–polymer interactions. Acid-functionalized SWCNTs were more effective for reinforcing PPS-NH₂ than epoxy-functionalized SWCNTs, attributed to the formation of a larger number of covalent bonds, albeit led to a smaller increase in the electrical conductivity of the polymer. The results herein offer useful insights into the development of multifunctional CNT-reinforced thermoplastic composites for a wide variety of applications.     

Tailored dielectric and mechanical properties of noncovalently functionalized carbon nanotube/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) nanocomposites

The preparation of high‐dielectric poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) (SEBS) composites containing functionalized single‐walled carbon nanotubes (f‐SWCNTs) noncovalently appended with dibutyltindilaurate are reported herein. Transmission electron microscopy and X‐ray photoelectron and Raman spectroscopy confirmed the noncovalent functionalization of the SWCNTs. The SEBS‐f‐SWCNT composites exhibited enhanced mechanical properties as well as a stable and high dielectric constant of approximately 1000 at 1 Hz with rather low dielectric loss at 2 wt% filler content. The significantly enhanced dielectric property originates from the noncovalent functionalization of the SWCNTs that ensures good dispersion of the f‐SWCNTs in the polymer matrix. The f‐SWCNTs also acted as a reinforcing filler, thereby enhancing the mechanical properties of the composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Functionalization of multi‐walled carbon nanotubes with poly(ε‐caprolactone) using click chemistry

Multi‐walled carbon nanotubes (MWNTs) were covalently functionalized with poly(ε‐caprolactone) (PCL) using click chemistry. First, chlorine moiety‐containing PCL was synthesized by the copolymerization of α‐chloro‐ε‐caprolactone with ε‐caprolactone monomer using ring opening polymerization, and further converted to azide moiety‐containing PCL. The alkyne‐functionalized MWNTs were prepared with the treatment of p‐amino propargyl ether using a solvent free diazotization procedure. The covalent functionalization of alkyne‐derived MWNTs with azide moiety‐containing PCL was accomplished using Cu(I)‐catalyzed [3+2] Huisgen dipolar cycloaddition click chemistry. The PCL‐functionalization of MWNTs was confirmed by the measurements of Fourier transform infra‐red, NMR, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Graft copolymerization of thiophene onto polystyrene synthesized via nitroxide‐mediated polymerization and its polymer − clay nanocomposite

A new strategy for graft copolymerization of thiophene onto a polystyrene (PSt) backbone by a multi‐step process is suggested and the effects of an organoclay on the final properties of the graft copolymer sample are described. For this purpose, first poly(styrene‐co‐4‐chloromethyl styrene) [P(St‐co‐CMSt)] was synthesized via nitroxide‐mediated polymerization. Afterwards, the chlorine groups of P(St‐co‐CMSt) were converted to thiophene groups using the Kumada cross‐coupling reaction and thiophene‐functionalized PSt multicenter macromonomer (ThPStM) was synthesized. The graft copolymerization of thiophene monomers onto PSt was initiated by oxidized thiophene groups in the PSt chains after addition of ferric chloride (FeCl₃), an oxidative catalyst for polythiophene synthesis, and FeCl₃‐doped polythiophene was chemically grafted onto PSt chains via oxidation polymerization. The graft copolymer obtained was characterized by ¹H NMR and Fourier transform infrared spectroscopy, and its electroactivity behavior was verified under cyclic voltammetric conditions. Finally, PSt‐g‐PTh/montmorillonite nanocomposite was prepared by a solution intercalation method. The level of dispersion of organoclay and the microstructure of the resulting nanocomposite were probed by means of XRD and transmission electron microscopy. It was found that the addition of only a small amount of organoclay (5 wt%) was enough to improve the thermal stabilities of the nanocomposite.© 2013 Society of Chemical Industry     

Edge‐functionalized graphene nanoplatelets with polystyrene by atom transfer radical polymerization: grafting through carboxyl groups

The surface modifier 3‐((4‐hydroxybutoxy)dimethylsilyl)propyl methacrylate (CD), which contains a double bond and a hydroxyl group, was synthesized through a coupling reaction of 1,4‐butanediol and (3‐methacryloxypropyl)dimethylchlorosilane. Subsequently, graphene oxide (GO) was functionalized with different amounts of CD from its edge carboxyl groups. Then, grafting through atom transfer radical polymerization of styrene in the presence of various amounts of the edge‐functionalized GO was carried out to evaluate the effect of graphene loading along with graft density. A peak at 3.8 ppm in the ¹H NMR spectrum of CD associated with the methylene adjacent to the Si–O group indicated a successful coupling reaction. Attachment of CD on the edges of GO was evaluated using X‐ray photoelectron and Fourier transform infrared spectroscopies. Expansion of GO interlayer spacing by functionalization was evaluated using X‐ray diffraction. The ordered and disordered crystal structure of carbon was studied using Raman spectroscopy. The close I_D/I_G values for GO and various kinds of functionalized graphenes show the preserved graphitic crystallite size. Relaxation behaviour of polystyrene chains in the presence of graphene nanoplatelets and also the effect of graft content on chain confinement were studied using differential scanning calorimetry. High‐graft‐density nanocomposites show higher glass transition temperatures. Morphology of graphene nanoplatelets was studied using scanning electron and transmission electron microscopies. The flat and smooth morphology of graphene nanoplatelets is disturbed and also the transparency of the nanoplatelets decreases during the oxidation and functionalization processes. © 2014 Society of Chemical Industry     

Terminal functionalized hydroxyl‐terminated polybutadiene: An energetic binder for propellant

We report the functionalization of hydroxyl terminated polybutadiene (HTPB) backbone by covalently attaching 1‐chloro‐2, 4‐dinitrobenzene (DNCB) at the terminal carbon atoms of the HTPB. The modification of the HTPB by the DNCB does not alter the unique physico–chemical properties and the microstructure of the parent HTPB. IR, ¹H‐NMR, ¹³C‐NMR, size exclusion chromatography (SEC) and absorption spectroscopy studies prove that the DNCB molecules are covalently attached to the terminal carbon atoms of the HTPB. The π electron delocalization owing to long polymer chain, strong electron withdrawing effect of the DNCB molecule are the major driving forces for the covalent attachment of the DNCB at the terminal carbon atom of the HTPB. We are the first to observe the existence of intermolecular hydrogen bonding between the terminal hydroxyl groups of the HTPB. IR study shows that the attached DNCB molecules at the terminal carbon atoms of the HTPB breaks the intermolecular hydrogen bonding between the HTPB chains and forms a hydrogen bonding between the NO₂ groups of the DNCB and the OH groups of the HTPB. Absorption spectral study of the modified HTPB indicates the better delocalization of π electron of butadiene due to the strong electron withdrawing effect of the DNCB molecules. Theoretical calculation also supports the existence of hydrogen bonding between the OH and NO₂ groups. Theoretical calculation shows that the detonation performance of both the DNCB and the HTPB‐DNCB are promising. HTPB‐DNCB is the new generation energetic binder which has potential to replace the use of HTPB as binder for propellant.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of magnetic citric‐acid‐functionalized graphene oxide and its application in the removal of methylene blue from contaminated water

A magnetic nanocomposite of citric‐acid‐functionalized graphene oxide was prepared by an easy method. First, citric acid (CA) was covalently attached to acyl‐chloride‐functionalized graphene oxide (GO). Then, Fe₃O₄ magnetic nanoparticles (MNPs) were chemically deposited onto the resulting adsorbent. CA, as a good stabilizer for MNPs, was covalently attached to the GO; thus MNPs were adsorbed much more strongly to this framework and subsequent leaching decreased and less agglomeration occurred. The attachment of CA onto GO and the formation of the hybrid were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction spectrometry and transmission electron microscopy. The specific saturation magnetization of the magnetic CA‐grafted GO (GO‐CA‐Fe₃O₄) was 57.8 emu g^?1 and the average size of the nanoparticles was found to be 25 nm by transmission electron microscopy. The magnetic nanocomposite was employed as an adsorbent of methylene blue from contaminated water. The adsorption tests demonstrated that it took only 30 min to attain equilibrium. The adsorption capacity in the concentration range studied was 112 mg g^?1. The GO‐CA‐Fe₃O₄ nanocomposite was easily manipulated in an external magnetic field which eases the separation and leads to the removal of dyes. Thus the prepared nanocomposite has great potential in removing organic dyes. © 2014 Society of Chemical Industry     

Water-soluble carbon nanotubes through sugar azide functionalization

In this work we report a covalent functionalization of pristine single-walled carbon nanotubes (SWCNTs) directly with three sugar azides, 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl, 2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl or 2,3,4,6-tetra-O-acetyl-β-d-mannopyranosyl azide. Microwave-assisted functionalization was carried out for SWCNTs prepared with the HiPCO method. The as-prepared, new type of sugar-functionalized SWCNTs were analyzed by Raman and IR spectroscopy. Deacetylation of the functionalized tubes by sodium methoxide yielded nitrogen-linked, sugar-functionalized carbon nanotubes (CNTs) that formed stable dispersions in water. Reactivity of the sugar azides towards SWCNTs was estimated from the solubility experiments. The water solubility was found to be highest for galactopyranosyl and lowest for gluco- and mannopyranosyl derivatives.     

Fabrication of pH‐ or temperature‐responsive single wall carbon nanotubes via a graft from photopolymerization

An ultraviolet light initiated “graft from” polymerization method to fabricate polymer‐functionalized single wall carbon nanotubes (SWNTs) with pendant pH‐ and temperature‐responsive polymer chains is utilized. The attached polymer chains, formed from methacrylic acid and poly(ethylene glycol) methyl ether methacrylate monomers, are well established for its pH‐responsive swelling/deswelling behavior. This special property was utilized here to control the aqueous dispersibility of the carbon nanotubes. Furthermore, poly(N‐isopropylacrylamide), a temperature‐responsive polymer, was utilized in the fabrication of SWNTs whose dispersibility was dependent on solution temperature. The morphology of the polymer‐functionalized carbon nanotubes was characterized by scanning electron microscopy (SEM) before and after functionalization. Environmental SEM was used to further characterize the morphology of the functionalized SWNTs. In addition, covalent bonding of the polymer to the carbon nanotube surface was established using Raman and Fourier transform infrared spectroscopic techniques. The physical and chemical properties of the functionalized nanotubes were further characterized by energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2980–2986, 2012     

Grafting of polymer chains on the surface of carbon nanotubes via nitroxide radical coupling reaction

Poly(butylene succinate) (PBS) was grafted on the surface of TEMPO (2,2,6,6‐tetramethyl‐1‐piperidinyloxy) modified multi‐walled carbon nanotubes (MWCNTs) via a nitroxide radical coupling reaction. TEMPO functionalized MWCNTs (MWCNTs‐g‐TEMPO) were synthesized using the Cu(I)‐catalyzed azide/alkyne click chemistry approach and the covalent bond of the nitroxide moieties onto the MWCNTs was confirmed via electron paramagnetic resonance (EPR) spectroscopy. The PBS grafting on the sidewalls of MWCNTs was carried out in solution via peroxide‐induced formation of macroradicals and it was confirmed by EPR and attenuated total reflectance Fourier transform infrared analysis. Preliminary rheological and calorimetric analyses revealed that the grafting improves both the quality of stress transfer across the polymer ? nanotube interface and the degree of dispersion of the filler, which also exhibited a moderate nucleating action on the PBS. Overall, our results demonstrate that nitroxide radical coupling is an efficient and feasible ‘grafting to’ method to covalently bond polymer chains on MWCNTs with possible advantages in the final properties of the polymer nanocomposites. © 2015 Society of Chemical Industry     

Postfunctionalization strategy for developing polyphosphazene with a high loading of highly polar molecules in the side arms

A new postfunctionalization strategy for developing polyphosphazene functionalized with a high density of highly polar molecules was explored, and the moiety loading was up to 0.84 per unit. A polyphosphazene with N,N‐dialkyl‐substituted aniline as side chains was first synthesized by a direct substituted reaction, and then post azo coupling of p‐nitrobenzenediazonium fluoroborate toward the aniline groups afforded functionalized polyphosphazenes with highly polar molecules. The structural characterization was performed with ¹H‐NMR, IR, and ultraviolet–visible spectroscopy and gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2989–2993, 2003     

Synthesis and ultraviolet‐curing behaviors of vinyl ether functionalized polyurethane oligomers

The vinyl ether functionalized oligomer is one of the most basic components of vinyl ether functionalized materials for cationic UV‐curable coatings. In this study, three types of vinyl ether functionalized polyurethane oligomers (i.e., polyether, polyester, and polydimethylsiloxane) were synthesized with diisocyanate, diol, and hydroxyethyl vinyl ether. These oligomers were characterized by IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The effect of the raw material ratio on the oligomer, UV‐curing behaviors, and thermal properties of these oligomers were investigated. The UV‐curing behavior was analyzed by real‐time Fourier transform infrared spectroscopy. The vinyl ether terminated polyester urethane oligomer exhibited better UV curing, with a higher final conversion and maximum UV‐curing rates. In addition, the light intensity was enhanced for oligomers with better UV‐curing properties. Research on these vinyl ether functionalized oligomers is essential to the development and applications of cationic vinyl ethers systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40501.     

Network formation by aza‐Michael addition of primary amines to vinyl end groups of enzymatically synthesized poly(glycerol adipate)

A highly efficient approach for the synthesis of polyester‐based networks via aza‐Michael addition of primary amines to α,β‐unsaturated (vinyl) end groups of poly(glycerol adipate) (PGA) was achieved. By acylation of PGA with 6‐(Fmoc‐amino)hexanoic acid side chains via Steglich esterification, protected amine‐functionalized PGA was obtained. This was followed by the removal of fluorenylmethyloxycarbonyl (Fmoc) protecting groups and the synthesis of PGA‐based networks under catalyst‐free conditions. The successful conjugate addition of primary amines to vinyl end groups and network formation were confirmed using ¹³C magic angle spinning NMR and Fourier transform infrared spectroscopy. Network heterogeneity and defects were quantitatively investigated using ¹H double‐quantum NMR spectroscopy. Finally, a hydrogel was prepared with potential biomedical applications.     

Surfactant-free assembling of functionalized single-walled carbon nanotube buckypapers

The electrical and textural properties of single-walled carbon nanotube buckypapers were tunned through chemical functionalization processes. Single-walled carbon nanotubes (SWCNTs) were covalently functionalized with three different chemical groups: Carboxylic acids (-COOH), benzylamine (-Ph-CH₂-NH₂), and perfluorooctylaniline (-Ph-(CF₂)₇-CF₃). Functionalized SWCNTs were dispersed in water or dimethylformamide (DMF) by sonication treatments without the addition of surfactants or polymers. Carbon nanotube sheets (buckypapers) were prepared by vacuum filtration of the functionalized SWCNT dispersions. The electrical conductivity, textural properties, and processability of the functionalized buckypapers were studied in terms of SWCNT purity, functionalization, and assembling conditions. Carboxylated buckypapers demonstrated very low specific surface areas (< 1 m²/g) and roughness factor (R_a = 14 nm), while aminated and fluorinated buckypapers exhibited roughness factors of around 70 nm and specific surface areas of 160-180 m²/g. Electrical conductivity for carboxylated buckypapers was higher than for as-grown SWCNTs, but for aminated and fluorinated SWCNTs it was lower than for as-grown SWCNTs. This could be interpreted as a chemical inhibition of metallic SWCNTs due to the specificity of the diazonium salts reaction used to prepare the aminated and fluorinated SWCNTs. The utilization of high purity as-grown SWCNTs positively influenced the mechanical characteristics and the electrical conductivity of functionalized buckypapers.     

Synthesis of click‐coupled graphene sheets with hyperbranched polyurethane: Effective exfoliation and enhancement of nanocomposite properties

Graphene oxide (GO) was functionalized with hyperbranched polyurethane (HBPU) via click coupling between azide‐functionalized HBPU and alkynyl‐decorated GO. HBPU‐functionalized GO composites of various compositions were prepared. The azide‐containing HBPU was characterized using Fourier‐transform infrared (FT‐IR) spectroscopy and ¹H‐nuclear magnetic resonance spectroscopy. The HBPU‐functionalized GO composites were characterized using transmission electron microscopy and FT‐IR spectroscopy. The functionalized GO showed excellent dispersion in the HBPU matrix, giving composites with enhanced mechanical and thermal properties. The material properties were effectively regulated by click‐coupled exfoliation of GO with HBPU, enabling the production of high‐performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44631.     

Deposition of functionalized single wall carbon nanotubes through matrix assisted pulsed laser evaporation

Single-wall carbon nanotubes (SWCNTs) functionalized with oxygen-containing groups were deposited onto glass substrates by matrix assisted pulsed laser evaporation (MAPLE). The experiments were performed by subjecting ultraviolet laser pulses (KrF¹ excimer laser, 248 nm wavelength) to frozen SWCNT-toluene targets placed in a parallel plane a few cm in front of the substrate. The morphology, structure, and chemical composition of the deposited materials were studied through atomic force microscopy, high resolution transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The influence of the laser fluence on the material structure was investigated. The results indicate that the functionalized SWCNTs can be transferred by MAPLE at low laser fluences without the alteration of the structure of the initial material used as targets in MAPLE experiments. An increase of the fluence leads to the decomposition of the functional groups, mainly carboxylic acid groups, without degradation of the SWCNT structure whereas, at the highest fluences, the amorphization and even coalescence of the carbon nanotubes takes place.