Preparation and characterization of polydiphenylamine/multi‐walled carbon nanotube composites

We describe the synthesis of methane sulfonic acid (MeSA)‐doped poly(diphenylamine) (PDPA) with carboxylic groups containing multi‐walled carbon nanotubes (c‐MWNTs) via in situ polymerization. Diphenylamine monomers were adsorbed on to the surface of c‐MWNTs and polymerized to form PDPA/c‐MWNT composites. SEM and TEM images indicated two different types of materials: the thinner fibrous phase and the larger globular phase. The individual fibrous phase had a diameter around 100–130 nm, which should be the carbon nanotubes (diameter 20–30 nm) coated with a PDPA layer. The structure of PDPA/c‐MWNT composites was characterized by FTIR, UV‐visible spectroscopy and X‐ray diffraction patterns. The electrical conductivities of PDPA/c‐MWNT composites were much higher than that of PDPA without c‐MWNTs. Copyright © 2006 Society of Chemical Industry     

Doped polyaniline/multiwalled carbon nanotube composites: Preparation and characterization

Polyaniline (PANI)/multiwalled carbon nanotube (MWNT) composites with a uniform tubular structure were prepared from in situ polymerization by dissolving amino‐functionalized MWNT (a‐MWNT) in aniline monomer. For this the oxidized multiwalled nanotube was functionalized with ethylenediamine, which provided ethylenediamine functional group on the MWNT surface confirmed by Fourier‐transform infrared spectra (FT‐IR). The a‐MWNT was dissolved in aniline monomer, and the in situ polymerization of aniline in the presence of these well dispersed nanotubes yielded a novel tubular composite of carbon nanotube having an ordered uniform encapsulation of doped polyaniline. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanotubes were coated with a PANI layer. The thermal stability and electrical conductivity of the PANI /MWNTs composites were characterized by thermogravimetric analysis (TGA) and conventional four‐probe method respectively. Compared with pure PANI, the electrical conductivity and the decomposition temperature of the MWNTs/PANI composites increased with the enhancement of MWNT content in PANI matrix. POLYM. COMPOS., 34:1119–1125, 2013. © 2013 Society of Plastics Engineers     

Poly (N‐methylaniline)/multi‐walled carbon nanotube composites—Synthesis,characterization, and electrical properties

This study described the synthesis of hydrochloric acid (HCl)‐doped poly (N‐methylaniline) (PNMA) with carboxylic groups containing multi‐walled carbon nanotubes (c‐MWNTs) via in situ polymerization. Based on the π–π electron interaction between c‐MWNTs and the N‐methylaniline monomer and the hydrogen bond interaction between the carboxyl groups of c‐MWNTs and imine groups of N‐methylaniline monomers, N‐methylaniline molecules were adsorbed on the surface of c‐MWNTs and polymerized to form PNMA/c‐MWNT composites. Scanning electron microscopy images showed that both the thinner fibrous phase and the larger block phase could be observed. The individual fibrous phases had diameters from several tens to hundreds of nanometers, depending on the PNMA content. Transmission electron microscopy proved that PNMA/c‐MWNTs composite fibrous phases were core (c‐MWNT)‐shell (PNMA) tubular structures. The structure of PNMA/c‐MWNT composites was characterized by FTIR, UV–vis spectra, and X‐ray diffraction patterns. The electrical conductivities of PNMA/c‐MWNT composites were much higher than that of PNMA without c‐MWNTs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2356–2361, 2006     

Conducting polymer composites of multiwalled carbon nanotube filled doped polyaniline

A multiwalled carbon nanotube (c‐MWNT)/polyaniline (PANI) composite was synthesized by an in situ chemical oxidative polymerization process. With the carbon nanotube loading increased from 0 to 30 wt %, the conductivity also increased and became weakly temperature‐dependent. Fourier transform infrared spectroscopy studies showed that the synthesis by an in situ process led to effective site‐selective interactions between the quinoid ring of the PANI and the multiwalled nanotubes, facilitating charge‐transfer processes between the two components. The morphological analysis indicated that the c‐MWNTs were well dispersed and isolated, and the tubes became crowded proportionally to the weight percentage of c‐MWNTs used in the composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of composites of polyaniline nanorods and multiwalled carbon nanotubes coated with polyaniline

Composites of polyaniline (PANI) nanorods and multiwalled carbon nanotubes (MWNTs) coated with PANI were prepared by in situ polymerization with perchloric acid as a dopant. Transmission electron microscopy images showed that the coexisting composites of PANI nanorods and MWNTs coated with PANI were formed at low MWNT contents. The interaction between MWNTs and PANI was proved by Fourier transform infrared and ultraviolet–visible spectra. The electrical conductivity of a dedoped PANI/MWNT composite with a 16.3 wt % concentration of MWNTs reached 3.0 × 10^?3 S/cm, which was 6 orders of magnitude higher than that of dedoped PANInanorods. The results also showed that coexisting composites of PANI nanorods and MWNTs coated with PANI had high electrochemical activity and good cyclic stability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Efficient dispersion of multi‐walled carbon nanotubes by in situ polymerization

Multi‐walled carbon nanotube (MWNT)‐reinforced polyimide nanocomposites were synthesized by in situ polymerization of monomers in the presence of acylated MWNTs. The acyl groups associated with the MWNTs participated in the reaction through the formation of amide bonds. This process enabled uniform dispersion of MWNT bundles in the polymer matrix. The resultant MWNT–polyimide nanocomposite films were optically transparent with significant mechanical enhancement at a very low loading (0.5 wt%). Evidence has been obtained for improved interactions between the nanotubes and the matrix polymer. Copyright © 2006 Society of Chemical Industry     

Mechanical and thermal properties of functionalized multiwalled carbon nanotubes and multiwalled carbon nanotube–polyurethane composites

Multiwalled carbon nanotube (MWNT)–polyurethane (PU) composites were obtained by an in situ polycondensation approach. The effects of the number of functional groups on the dispersion and mechanical properties were investigated. The results showed that the functionalized MWNTs had more advantages for improving the dispersion and stability in water and N,N′‐dimethylformamide. The tensile strength and elongation at break of the composites exhibited obvious increases with the addition of MWNT contents below 1 wt % and then decreases with additions above 1 wt %. The maximum values of the tensile strength and elongation at break increased by 900 and 741%, respectively, at a 1 wt % loading of MWNTs. Differential scanning calorimetry measurements indicated that the addition of MWNTs resulted in an alteration of the glass‐transition temperature of the soft‐segment phase of MWNT–PU. Additionally, new peaks near 54°C were observed with differential scanning calorimetry because of the microphase‐separation structures and alteration of the segment molecular weights of the hard segment and soft segment of PU with the addition of MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of surface modification with 3‐aminopropyltriethoxysilane on structure and mechanical property of multiwalled carbon nanotube/polycarbonate composites

Hydroxyl functionalized multiwalled carbon nanotubes (H‐MWNTs) were silanized using 3‐aminopropyltriethoxysilane (APTES) in order to improve the dispersion and interfacial interaction in composites. MWNT/polycarbonate (PC) composites filled with H‐MWNTs and silanized MWNTs (S‐MWNTs) were fabricated by melt mixing and injection molding. Fourier transform infrared spectrometry (FTIR) and energy dispersion X‐ray spectroscopy (EDS) were employed to prove the presence of APTES on the surface of S‐MWNTs. In addition, thermogravimetric analysis (TGA) was used to evaluate the relative amount of introduced APTES. The microstructure and mechanical property of both composites were investigated by scanning electron microscopy (SEM), transmission electron microscope (TEM), tensile test and dynamic mechanical analysis (DMA). The SEM and TEM images showed that S‐MWNT/PC composites had better dispersion and interfacial adhesion than H‐MWNT/PC composites. A reinforcing and toughening effect on tensile behavior of composites was obtained after silane functionalization. The storage modulus of composites increased markedly as a function of MWNTs content, especially for the composites with S‐MWNTs. In summary, the silanization can improve the dispersion of MWNTs and the interfacial adhesion between MWNTs and PC so as to enhance the mechanical properties of composites. POLYM. COMPOS., 37:1914–1923, 2016. © 2015 Society of Plastics Engineers     

Surface resistivity and rheological behaviors of carboxylated Multiwall carbon nanotube‐filled PET composite film

Multiwalled carbon nanotube (MWNT) nanocomposites with poly(ethylene terephthalate) (PET) were prepared via in situ polymerization. The refluxing time was more important factor than the sonication time for giving carboxylic groups onto the surface of MWNT. Acid‐MWNT prepared was well dispersed in ethylene glycol, whereas the neat‐MWNT agglomerated and sedimented at the bottom. The viscosity of the composites increased with the addition of MWNT, but PET/acid‐MWNT composite showed lower viscosity than PET/neat‐MWNT because of the damage of MWNT by acid treatment and copolymerization effect by the reaction between carboxylic groups of MWNT and PET. PET/acid‐MWNT composite film showed lower surface resistivity than PET/neat‐MWNT composite film. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 900–904, 2006     

Effects of functionalized MWNTs with GMA on the properties of PMMA nanocomposites

The acid modification of multiwall carbon nanotubes (MWNTs) was performed by an HNO₃/H₂SO₄ solution. The glycidyl methacrylate (GMA) undergoing an opening‐ring was grafted onto the surface of acid‐modified MWNTs. The surface properties of MWNTs were investigated by Fourier transform infrared spectrometer (FTIR), Raman spectra, transmission electron microscopy (TEM), X‐ray diffraction, and thermogravimeric analysis. Then the MWNTs/ poly(methyl methacrylate) (PMMA) nanocomposites were prepared by in situ polymerization. The tribological and dielectric properties of nanocomposites were studied. As a result, GMA was grafted on the surface of MWNTs. The tribological and dielectric properties of MWNTs/ PMMA nanocomposites were improved as the content of the surface‐modified MWNT increased. The marked improvement in tribological and dielectric properties were attributed to the good dispersion of MWNTs that were bonded with C?C on the surface that participated in the polymerization of MMA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermomechanical and water‐responsive shape memory properties of carbon nanotubes‐reinforced hyperbranched polyurethane composites

Shape memory composites of hyperbranched polyurethane (HBPU) and acid‐treated multi‐walled carbon nanotubes (MWNTs) were prepared using an in situ polymerization method. HBPUs with different hard segments contents were synthesized via the A₂ + B₃ approach using poly(ethylene glycol) (PEG) as a soft segment, 4,4′‐methylene bis(phenylisocynate), castor oil, and 1,4‐butanediol as hard segment. Compared to HBPU, the HBPU/MWNT composites showed faster shape recovery and double the shape recovery stress in the thermomechanical shape memory test, which was dependent on the MWNTs content and HBPU hard segment content. The water‐responsive shape memory effect of HBPU/MWNT composites was considered to result from the combined contribution of hydrophilic PEG and well dispersed MWNTs in highly branched HBPU molecules. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and characterization of conducting poly(diphenylamine) entrapped polyurethane network electrolyte

Composites of thermoplastic polyurethane (TPU) with poly(diphenylamine) (PDPA) were prepared by entrapping diphenylamine (DPA) molecules into the matrix of TPU and polymerizing DPA within the TPU matrix. Swelling rate of the parent TPU and the composites in 1M LiClO₄ in propylene carbonate solution were compared to understand the influence of the presence of PDPA in the composite in altering the morphology, conductivity, and electrolyte behavior. The nitrogen atoms in the PDPA interact and are likely to form hydrogen bonding with the carbonyl and ether groups in TPU. As a result, different morphology, thermal, and impedance behavior were witnessed for the composites in comparison to TPU. Results from differential scanning calorimetry, scanning electron microscopy (SEM), thermogravimetric analysis, and ac impedance measurements were obtained as supporting evidences. An increase in glass transition temperature for the composite in comparison to TPU infers the increase in phase mixing of soft and hard segment of TPU. The SEM micrograph shows the presence of fibrillar morphology of PDPA molecules in the composite. The ionic conductivity of the swelled composite was 1‐fold higher than that of pure TPU. A schematic representation showing the interaction of PDPA molecules with TPU is presented. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 611–617, 2006     

Preparation and properties of multiwalled carbon nanotube/polycaprolactone nanocomposites

Multiwalled carbon nanotube/polycaprolactone nanocomposites (MWNT/PCL) were prepared by in situ polymerization, whereby as‐received MWNTs (P‐MWNTs) and purified MWNTs (A‐MWNTs) were used as reinforcing materials. The A‐MWNTs were purified by nitric acid treatment, which introduced the carboxyl groups (COOH) on the MWNT. The micrographs of the fractured surfaces of the nanocomposites showed that the A‐MWNTs in A‐MWNT/PCL were better dispersed than P‐MWNTs in PCL matrix (P‐MWNT/PCL). Percolation thresholds of the P‐MWNT/PCL and A‐MWNT/PCL, which were studied by rheological properties, were found at ～2 wt % of the MWNT. The conductivity of the P‐MWNT/PCL was between 10^?1 and 10^?2 S/cm by loading of 2 wt % of MWNT although that of the A‐MWNT/PCL reached ～10^?2 S/cm by loading of 7 wt % of MWNT. The conductivity of the P‐MWNT/PCL was higher than that of the A‐MWNT/PCL at the entire range of the studied MWNT loading, which might be due to the destruction of π‐network of the MWNT by acid treatment, although the A‐MWNT/PCL was better dispersed than the P‐MWNT/PCL. The amount of the MWNT at which the conductivity of the nanocomposite started to increase was strongly correlated with the percolation threshold. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1957–1963, 2007     

Isothermal and nonisothermal crystallization kinetics of poly(ε‐caprolactone)/multi‐walled carbon nanotube composites

Differential scanning calorimeter (DSC) and polarized optical microscopy (POM) have been used to investigate the isothermal and nonisothermal crystallization behavior of poly(ε‐caprolactone) (PCL)/multi‐walled carbon nanotube (MWNT) composites. PCL/MWNT composites have been prepared by mixing the PCL polymer with carboxylic groups containing multi‐walled carbon nanotubes (c‐MWNTs) in tetrahydrofuran solution. Raman spectrum of c‐MWNT indicated the possible presence of carboxylic acid groups at both ends and on the sidewalls of the MWNTs. The TEM micrograph showed that the c‐MWNT is well separated and uniformly dispersed in the PCL matrix. DSC isothermal results showed that the introduction of c‐MWNT into the PCL initiates strongly heterogeneous nucleation, which induced a change of the crystal growth process. The activation energy of PCL significantly decreases by adding 0.25 wt% c‐MWNT into PCL/c‐MWNT composites and then increases as c‐MWNT content increases. The result demonstrates that the addition of c‐MWNT into PCL induces the heterogeneous nucleation at lower c‐MWNT content and then inhibits the polymer chain transportation ability during crystallization at higher c‐MWNT content. In this study, we have also studied the nonisothermal crystallization kinetics and melting behavior of PCL/c‐MWNT composites at various cooling rates. The correlation among isothermal and nonisothermal crystallization kinetics and melting behavior of PCL/c‐MWNT composites can be also discussed. POLYM. ENG. SCI., 46:1309–1317, 2006. © 2006 Society of Plastics Engineers     

Synthesis and characterization of a polymer/multiwalled carbon nanotube composite and its application in the hydration of ethylene oxide

Multiwalled carbon nanotubes (MWNTs) were incorporated into the crosslinking network of a styrene–divinylbenzene copolymer (PS–DVB) via suspension polymerization. The prepared crosslinking PS–DVB with MWNTs was first treated with chloromethyl methyl ether to introduce chloromethyl groups through Friedel–Craft reaction; then, the chloromethylation product was reacted with trimethyl amine to obtain the target polymer/carbon nanotube composite: PS–DVB/MWNT ion‐exchange resin. The obtained composite was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy, and X‐ray photoelectron spectroscopy. The results show the successful incorporation of MWNTs into the polymer network. The physical and chemical properties of the PS–DVB/MWNT ion‐exchange resin were nearly the same as those of the controlled sample. With its excellent antiswelling properties, the catalytic behavior of the polymer composite was examined in the hydration of ethylene oxide. Also, it demonstrated excellent stability as a catalyst without a decline in conversion and selectivity in a long‐time run. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of thermally conductive polystyrene/carbon nanotubes composites

Thermally conductive polystyrene (PS)/multi‐walled carbon nanotubes (MWNTs) nanocomposites was prepared through a simple solution‐evaporation method assisted by ultrasonic irradiation. To enhance the dispersion of MWNTs in PS, MWNTs were chemically functionalized with poly(styrene‐co‐maleic anhydride) (SMA) (MWNT‐g‐SMA), which had benzene group and exhibited strong affinity with PS. The thermal conductive properties of PS increased and the mechanical properties decreased in presence of MWNTs, while by addition of MWNT‐g‐SMA, the properties of the composites can be improved to some extent. The thermal conductivity can reach 0.89 W/m K for the composite with 33.3 vol % MWNT‐g‐SMA, which was four times higher than that of neat PS. A linear increase of the thermal conductivity was observed with increasing MWNTs‐g‐SMA content, and the Maxwell–Eucken model and the Agari model were used for theoretical evaluation. Compared with MWNT‐OH, MWNT‐g‐SMA with larger diameter exhibited diffused boundary with the PS matrix, resulting from the strong interfacial bonding of the two phases. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and properties of poly(butylene terephthalate)/multiwalled carbon nanotube nanocomposites prepared by in situ polymerization and in situ compatibilization

A novel cyclic initiator was synthesized from dibutyl tin(IV) oxide and hydroxyl‐functionalized multiwalled carbon nanotubes (MWNTs) and was used to initiate the ring‐opening polymerization of cyclic butylene terephthalate oligomers to prepare poly(butylene terephthalate) (PBT)/MWNT nanocomposites. The results of Fourier transform infrared and NMR spectroscopy confirmed that a graft structure of PBT on the MWNTs was formed during the in situ polymerization; this structure acted as an in situ compatibilizer in the nanocomposites. The PBT covalently attached to the MWNT surface enhanced the interface adhesion between the MWNTs and PBT matrix and, thus, improved the compatibility. The morphologies of the nanocomposites were observed by field emission scanning electron microscopy and transmission electron microscopy, which showed that the nanotubes were homogeneously dispersed in the PBT matrix when the MWNT content was lower than 0.75 wt %. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermal properties of the nanocomposites. The results indicate that the MWNTs acted as nucleation sites in the matrix, and the efficiency of nucleation was closely related to the dispersion of the MWNTs in the matrix. Additionally, the thermal stability of PBT was improved by the addition of the MWNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Dielectric properties of poly(vinylidene fluoride) composites based on Bucky gels of carbon nanotubes with ionic liquids

“Bucky gels” of carbon nanotubes were successfully prepared by grinding multi‐walled carbon nanotubes (MWNTs) and ionic liquids (ILs) for several hours. A series of poly(vinylidene fluoride) (PVDF) composites with Bucky gels was obtained through simple melt compounding. The Raman spectrum showed significant interaction among the ILs, MWNTs, and PVDF. The dielectric behavior of the PVDF composites based on unmodified and IL‐modified MWNTs was studied from 40 Hz to 30 MHz. The addition of ILs significantly enhanced the dielectric property of the PVDF/IL/MWNT ternary composites, which was much higher than that of the sum of PVDF/IL and PVDF/MWNT binary composites. The SEM results revealed that both MWNTs and ILs uniformly dispersed throughout the PVDF/IL/MWNT composites because of the strong interaction between them. The DSC and XRD results showed that the addition of ILs in the composites changed the crystallinity and crystal form of the PVDF. POLYM. COMPOS., 36:94–101, 2015. © 2014 Society of Plastics Engineers     

Fabrication of conducting polyaniline–multiwalled carbon nanotube nanocomposites and their use as templates for loading gold nanoparticles

A new and effective route to synthesize conducting polyaniline‐multiwalled carbon nanotube (PANI ‐f‐MWNT) nanocomposites (where ‘f’ denotes that the MWNTs have been functionalized) starting with amine‐protected 4‐aminophenol is reported. Aminophenol‐functionalized MWNTs were initially synthesized by functionalizing acyl chloride‐terminated nanotubes with N‐(tert‐butoxycarbonyl)‐4‐aminophenol followed by the in situ chemical oxidative grafting of aniline in the presence of ammonium persulfate as an oxidizing agent. Control of the morphology and thickness of the polymer–MWNT nanocomposites was achieved by varying the weight ratios of aniline monomers and MWNTs in the polymerization process. Fourier transform infrared spectroscopy was employed to characterize the initial changes in surface functionalities which also confirmed that PANI was covalently grafted to the MWNTs. Electron microscopy and UV‐visible absorption spectroscopy were employed to characterize the morphology and chemical structure of the resulting hybrids. The results obtained indicate that the structure of the MWNTs was not perturbed by the incorporation of PANI. The content of the polymer in the nanocomposites was determined thermogravimetrically, while the electrical conductivity was obtained using four‐probe measurements. The PANI ‐f‐MWNT nanocomposites were adopted as templates for further decoration with gold nanoparticles in solution, thus opening new possibilities for their prospective technological applications. Copyright © 2010 Society of Chemical Industry     

In situ synthesis and characterization of poly(2,5-benzoxazole)/multiwalled carbon nanotubes composites

This article reports the synthesis of poly(2,5-benzoxazole)/multiwalled carbon nanotubes (ABPBO/MWNT) composites by in situ polycondensation and their chemical and physical properties. The functional groups yielded from the surface modification of MWNTs by hydrochloric acids have been demonstrated to participate in the polymerization and thus led to the composites with homogenous dispersion of carbon nanotubes. The chemical structures and morphology of the afforded polymer composites have been fully characterized by FTIR, WAXD, UV-vis, TGA and SEM. The ABPBO/MWNT composites exhibit excellent thermal stability and greatly improved mechanical properties. The tensile modulus and tensile strength of the composites are 47% and 83%, respectively, higher than those of the polymer matrix. The dielectric constant of the composites is also significantly enhanced from 4 of the polymer matrix to 65 with the incorporation of 5 wt% MWNTs.