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     

Comparison of the properties of waterborne polyurethane/multiwalled carbon nanotube and acid‐treated multiwalled carbon nanotube composites prepared by in situ polymerization

A series of waterborne polyurethane (WBPU)/multiwalled carbon nanotube (CNT) and WBPU/nitric acid treated multiwalled carbon nanotube (A‐CNT) composites were prepared by in situ polymerization in an aqueous medium. The optimum nitric acid treatment time was about 0.5 h. The effects of the CNT and A‐CNT contents on the dynamic mechanical thermal properties, mechanical properties, hardness, electrical conductivity, and antistatic properties of the two kinds of composites were compared. The tensile strength and modulus, the glass‐transition temperatures of the soft and hard segments (T_gs and T_gh, respectively), and ΔT_g (T_gh − T_gs) of WBPU for both composites increased with increasing CNT and A‐CNT contents. However, these properties of the WBPU/A‐CNT composites were higher than those of the WBPU/CNT composites with the same CNT content. The electrical conductivities of the WBPU/CNT1.5 and WBPU/A‐CNT1.5 composites containing 1.5 wt % CNTs (8.0 × 10⁻⁴ and 1.1 × 10⁻³ S/cm) were nearly 8 and 9 orders of magnitude higher than that of WBPU (2.5 × 10⁻¹² S/cm), respectively. The half‐life of the electrostatic charge (τ_1/2) values of the WBPU/CNT0.1 and WBPU/A‐CNT0.1 composites containing 0.1 wt % CNTs were below 10 s, and the composites had good antistatic properties. From these results, A‐CNT was found to be a better reinforcer than CNT. These results suggest that WBPU/A‐CNT composites prepared by in situ polymerization have high potential as new materials for waterborne coatings with good physical, antistatic, and conductive properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3973–3985, 2005     

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     

Polymorphism of nylon‐6 in multiwalled carbon nanotubes/nylon‐6 composites

The effects of pristine and amino‐functionalized multiwalled carbon nanotubes (MWNTs) on the crystallization behaviors of nylon‐6 were investigated by differential scanning calorimetry and X‐ray diffraction. The results indicate the presence of polymorphism in nylon‐6 and its composites, which is dependent on the MWNTs concentration and the cooling rate. More MWNTs and slow cooling from the melt favors the formation of α crystalline form. With the increase in cooling rates, the crystallinity of neat nylon‐6 decreases, and that of the composites decreases initially but increases afterward. Moreover, the degree of crystallinity of the composites is higher than neat nylon‐6 under high cooling rates, counter to what is observed under low cooling rates. The heterogeneous nucleation induced by MWNTs and the restricted mobility of polymer chains are considered as the main factors. Furthermore, addition of MWNTs increases the crystallization rate of α crystalline form but amino‐functionalization of MWNTs weakens this effect. The influence of thermal treatment on the crystalline structure of MWNTs/nylon‐6 composites is also discussed. A γ–α phase transition takes place at lower temperature for MWNTs/nylon‐6 composites than for nylon‐6. The annealing peaks of the composites annealed at 160 °C are higher than that of neat nylon‐6, and the highest annealing peak is obtained for amino‐functionalized MWNTs/nylon‐6 composites. This phenomenon is closely related to the different nucleation and recrystallization behaviors produced by various MWNTs in confined space. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1499–1512, 2006     

Strengthening of liquid crystalline polymer by functionalized carbon nanotubes through interfacial interaction and homogeneous dispersion

Multiwalled carbon nanotubes (MWCNTs) were functionalized with two types of chemical moieties (i.e. carboxylic, ? COOH and hydroxyl benzoic acid groups, ‐HBA) on their sidewalls in order to improve their interaction with a liquid crystalline polymer (LCP) and dispersion in LCP. We have investigated the rheological, mechanical, dynamic mechanical, and thermal properties in detail with variation of HBA‐functionalized MWCNTs in the LCP matrix. Effect of the dispersion state of the functionalized MWCNTs in the LCP matrix on the rheological behavior was also studied. The composites containing HBA‐functionalized MWCNTs showed higher complex viscosity, storage, and loss modulus than the composites with the same loading of raw MWCNTs and MWCNT‐COOH. It was suggested that the HBA‐functionalized MWCNTs exhibited a better dispersion in the polymer matrix and formed stronger CNT‐polymer interaction in the composites than the raw MWCNTs and MWCNT‐COOH, which was also confirmed by FESEM and FTIR studies. As a result, the overall mechanical performance of the HBA‐MWCNT‐LCP composites could be improved significantly. For example, the addition of 4 wt% HBA‐MWCNT to LCP resulted in the considerable improvements in the tensile strength and modulus of LCP (by 66 and 90%, respectively). Copyright © 2010 John Wiley & Sons, Ltd.     

Singlewall carbon nanotubes covered with polystyrene nanoparticles by in‐situ miniemulsion polymerization

This work is to make carbon nanotubes dispersible in both water and organic solvents without oxidation and cutting nanotube threads. Polystyrene‐singlewall carbon nanotube (PS‐SWNT) composites were prepared with three different methods: miniemulsion polymerization, conventional emulsion polymerization, and mixing SWNT with PS latex. The two factors, crosslinking and surface coverage of PS are important factors for the mechanical and electrical properties, including dispersion states of SWNT in various solvents. The PS‐SWNT composite prepared via a conventional emulsion polymerization showed SWNT bundles entirely covered with PS, whereas the PS‐SWNT composite prepared via a miniemulsion polymerization showed SWNT partially covered with crosslinked PS nanoparticles. The method of mixing SWNTs with PS latex did not show the well dispersed state of carbon nanotubes because PS was not crosslinked and was dissolved in a solvent, and nanotubes separated from PS precipitated. So the PS nanoparticle‐SWNT composite had lower electrical resistance, and higher mechanical strength than the other composites made by the latter two methods. As the amount of SWNT increases, the bare surface area of SWNT increases and the electrical conductivity increases in the composite made by the miniemulsion polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 573–584, 2006     

The effect of mixing methods on the dispersion of carbon nanotubes during the solvent-free processing of multiwalled carbon nanotube/epoxy composites

Several solvent-free processing methods to disperse multiwalled carbon nanotubes (MWCNTs) in bisphenol F-based epoxy resin were investigated, including the use of a microfluidizer (MF), planetary shear mixer (PSM), ultrasonication (US) and combinations. The processed mixture was cured with diethyl toluene diamine. Three complimentary techniques were used to characterize the dispersion of the MWCNTs in cured composite samples: optical microscopy, micro Raman spectroscopy, and scanning electron microscopy (SEM). For sample MF + PSM, optical micrographs and Raman images showed reduced agglomeration and a homogeneous distribution of MWCNTs in the epoxy matrix. SEM analysis of fractured specimen after tensile testing revealed breakage of nanotubes along the fracture surface of the composite. A comparison of the MWCNT dispersion in the epoxy samples processed using different methods showed that a combination of MF and PSM processing yields a more homogeneous sample than the PSM or US + PSM processed samples. Mechanical testing of the composites showed about 15% improvement in the tensile strength of samples processed by the MF + PSM method over other methods. Thermogravimetric analysis (TGA) results showed a small decrease in the onset degradation temperature for poorly dispersed samples produced by PSM compared with the well-mixed samples (MF + PSM). These results strongly suggest that the MF + PSM processing method yield better-dispersed and stronger MWCNT/epoxy composites. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Preparation and characterization of nematic polyazomethine/single‐walled carbon nanotube composites prepared by in situ polymerization

The synthesis and characterization of a series of nematic SWNT‐polyazomethine composites are described. The composites were prepared by in situ polymerization in the presence of 1 wt % of chemically modified SWNTs in such a way that they were either dispersed or covalently bonded to the polymeric matrix. The presence of the SWNTs did not alter the thermal behavior of the polymer matrix and, therefore, highly oriented fibers could be melt‐extruded from the composites at moderate temperatures, as revealed by structural and morphological studies. Preliminary tests on tensile properties indicate that strength and stiffness were improved when compared with fibers without CNTs, particularly when SWNTs were covalently bonded to the polymeric matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2361–2372, 2009     

Carbon Nanotube‐Adsorbed Electrospun Nanofibrous Membranes of Nylon 6

Summary: A simple and mass‐producible method was developed to densely assemble multiwalled carbon nanotubes (MWNTs) onto electrospun nylon 6 nanofibrous membranes. The process consists of dispersing the acid‐treated MWNTs in surfactant solutions or organic solvents, and dipping the nanofibrous membranes in the resulting dispersion for only 60 seconds, followed by the extraction of the surfactants in pure water and drying. The conductivity of the MWNT‐adsorbed nanofibrous membranes ranges from 2.2 × 10⁻² to 1.5 × 10⁻¹ S · cm⁻¹, as determined by the four probe method, which implies that the MWNTs are adsorbed uniformly and densely along the nanofibrous membranes. Furthermore, the results suggest that there is a strong interaction between the acid‐treated MWNTs and nylon 6. We also investigate the amount of MWNTs present in the membranes using thermogravimetric analysis.

SEM images of the non‐woven fibrous nylon 6 membranes after dip‐coating in a dispersion of the MWNTs in surfactant‐containing water.     

Grafting of polyaniline onto the surface of 4‐aminobenzoyl‐functionalized multiwalled carbon nanotube and its electrochemical properties

Polyaniline (PANi)‐grafted multiwalled carbon nanotube (MWNT) composite is prepared by a two‐step reaction sequence. MWNT is first functionalized with 4‐aminobenzoic acid in polyphosphoric acid/phosphorous pentoxide as a “direct” Friedel‐Crafts acylation reaction medium. The resultant 4‐aminobenzoyl‐functionalized MWNT is then treated with aniline using ammonium persulfate/aqueous hydrochloric acid to promote a chemical oxidative polymerization, leading to PANi‐grafted MWNT composite. The resultant composite is characterized by elemental analysis, Fourier‐transform infrared spectroscopy, wide‐angle X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, UV–vis absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and electrical conductivity measurement. The thermooxidative stability and electrical conductivity of PANi‐grafted MWNT composite are improved compared to those of PANi. Specifically, the electrical conductivity of PANi‐grafted MWNT is improved 10–900 times depending upon the level of doping. The capacitance of the composite is also greatly enhanced. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3103–3112, 2010     

Effective in situ synthesis and characteristics of polystyrene nanoparticle‐covered multiwall carbon nanotube composite

The higher surface area of selectively grown multiwall carbon nanotubes (MWCNTs) and the better proximity of the reactant species in in situ microemulsion polymerization were used to attach the polystyrene (PS) nanoparticles to the outer wall of MWCNTs. Attachment were achieved by replacing surfactant with PS nanoparticles. SEM showed that the MWCNTs and PS nanoparticles were distributed in the composite. High resolution transmission electron microscopy showed successful anchoring of PS nanoparticles to the outer wall of the MWCNTs. In addition, anchoring enhanced the Raman's G/D ratio of the MWCNT and degradation temperature in PS nanoparticles. A mechanism of attachment of PS nanoparticles on the outer wall of MWCNT was proposed. The modified MWCNTs exhibited good durability and dispersability in different organic solvents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1523–1529, 2009     

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.     

“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     

Epoxy/amine‐functionalized short‐length vapor‐grown carbon nanofiber composites

Short length vapor‐grown carbon nanofibers (VGCNFs) were functionalized with 4‐aminobenzoic acid in polyphosphoric acid/phosphorous phentoxide medium via “direct” Friedel‐Crafts acylation reaction to afford aminobenzoyl‐functionalized VGCNFs (AF‐VGCNFs). The AF‐VGCNFs as a cocuring agent were mixed with epoxy resin by simple mechanical stirring in methanol which was added to help efficient mixing. After evaporation of methanol, 4,4′‐methylenedianiline as a curing agent was added to the mixture, which was then cured at elevated temperatures. The resultant composites displayed uniform dispersion of AF‐VGCNFs into cured epoxy matrix. During curing process, the amine functionalities on AF‐VGCNF together with 4,4′‐methylenedianiline were expected to be involved in covalent attachment to the epoxy resin. As a result, both tensile modulus and strength of the composites were improved when compared with those of pure epoxy resin. Thus, the AF‐VGCNFs play a role as an outstanding functional additive, which could resolve both dispersion and interfacial adhesion issues at the same time by functionalization of VGCNFs and covalent bonding between the additive and matrix, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7473–7482, 2008     

Poly(butylene terephthalate)‐functionalized MWNTs by in situ ring‐opening polymerization of cyclic butylene terephthalate oligomers

Poly(butylene terephthalate) (PBT) had been covalently attached onto the surface of multiwalled carbon nanotubes (MWNTs) by a “grafting from” method based on in situ ring‐opening polymerization (ROP) of cyclic butylene terephthalate oligomers (CBT) using MWNT‐supported initiator (MWNT‐g‐Sn). The Sn? O bond grafted on the surface of MWNTs, which was confirmed by X‐ray photoelectron spectroscopy, provided the initiating sites for ROP of CBT. Fourier transformed infrared spectroscopy and nuclear magnetic resonance were used to confirm the chemical structure of MWNT‐graft‐PBT copolymer and emission transmission electron microscope was utilized to observe the nanostructure of the PBT functionalized MWNTs. A distinct core–shell structure with PBT layer as the shell could be observed after functionalization of PBT despite it was not uniform. The results of thermogravimetric analysis indicated that the grafting ratio of PBT was about 59.3%. Furthermore, the solubility of the PBT functionalized MWNTs in phenol/tetrachloroethane had also been investigated. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of polyaniline/multiwall carbon nanotube composite via inverse emulsion polymerization

The composite of polyaniline (PANI) and multiwall carbon nanotube carboxylated through acid treatment (c‐MWCNT) was synthesized by chemical oxidative polymerization in an inverse emulsion system. The resultant composites were compared with products from aqueous emulsion polymerization to observe the improvements in electrical conductivity, structural properties, and thermal stability obtained by this synthetic method. Prior to the inverse emulsion polymerization, MWCNT was treated with a strong acid mixture to be functionalized with carboxylic acid groups. Carboxylic acid groups on surfaces induced selective dispersibility between polar and nonpolar solvents because of the increase of hydrophilicity. As the content of c‐MWCNT was increased, the electrical conductivity was increased by a charge transport function from the intrinsic electrical conductivity of MWCNT and the formation of a highly ordered dense structure of PANI molecules on the surface of c‐MWCNT. The images observed with electron spectroscopy showed the capping of c‐MWCNT with PANI. The growth of additional ordered structures of PANI/c‐MWCNT composite, which was observed through wide‐angle X‐ray diffraction patterns, supported the capping by PANI. It was observed that the doping of the composite had a significant relationship with the concentration of dodecylbenzenesulfonic acid (DBSA). The thermal stability of PANI composite was improved by the addition of c‐MWCNT; this was thought to be related with structure ordering by inverse emulsion polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2255–2266, 2008     

Multifunctional poly(2,5‐benzimidazole)/carbon nanotube composite films

The AB‐monomer, 3,4‐diaminobenzoic acid dihydrochloride, was recrystallized from an aqueous hydrochloric acid solution and used to synthesize high‐molecular‐weight poly(2,5‐benzimidazole) (ABPBI). ABPBI/carbon nanotube (CNT) composites were prepared via in situ polymerization of the AB‐monomer in the presence of single‐walled carbon nanotube (SWCNT) or multiwalled carbon nanotube (MWCNT) in a mildly acidic polyphosphoric acid. The ABPBI/SWCNT and ABPBI/MWCNT composites displayed good solubility in methanesulfonic acid and thus, uniform films could be cast. The morphology of these composite films was studied by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The results showed that both types of CNTs were uniformly dispersed into the ABPBI matrix. Tensile properties of the composite films were significantly improved when compared with ABPBI, and their toughness (～200 MPa) was close to the nature's toughest spider silk (～215 MPa). The electrical conductivities of ABPBI/SWCNT and ABPBI/MWCNT composite films were 9.10 × 10^?5 and 2.53 × 10^?1 S/cm, respectively, whereas that of ABPBI film was 4.81 × 10^?6 S/cm. These values are ～19 and 52,700 times enhanced by the presence of SWCNT and MWCNT, respectively. Finally, without acid impregnation, the ABPBI film was nonconducting while the SWCNT‐ and MWCNT‐based composites were proton conducting with maximum conductivities of 0.018 and 0.017 S/cm, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1067–1078, 2010     

Large‐compound vesicle‐encapsulated multiwalled carbon nanotubes: A unique route to nanotube composites

A simple and unique strategy for preparation of large‐compound vesicle (LCV)‐encapsulated multiwalled carbon nanotubes (MWCNTs) has been developed, and this involves dispersion of MWCNTs in H‐shaped copolymers solution in DMF and encapsulation of MWCNTs with LCVs formed from hydrolysis and polycondensation of ? Si(OCH₃)₃ groups in the amphiphilic H‐shaped copolymers, (PTMSPMA)₂PEG(PTMSPMA)₂. This unique noncovalent approach is nondestructive, and the original structure of MWCNTs remains in the resultant MWCNTs/LCVs nanocomposites. The morphologies of nanocomposites LCVs/MWCNTs are controlled by the chain length ratio (N_PTMSPMA/N_PEG) of PTMSPMA to PEG. For the H‐shaped copolymers with N_PMSPMA/N_PEG ≤ 1.7, they self‐assembled to form LCVs with dense cavities in the presence of MWCNTs in a mixture of DMF/H₂O. When this ratio was more than 2.0, the large‐compound micelle‐wrapped MWCNTs were produced. This approach is potentially useful for preparation of MWCNTs encapsulated with various morphologies of polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3669–3679, 2009     

Molecular motion,morphology, and thermal properties of multiwall carbon nanotube/polysilsesquioxane composite

Diglycidyl ether of bisphenol A (DGEBA)‐bridged polyorganosiloxane precursors have been prepared successfully by reacting diglycidyl ether of bisphenol A epoxy resin with 3‐aminopropyltriethoxysilane. Acid‐modified and unmodified multiwalled carbon nanotube (MWCNT) were dispersed in the diglycidyl ether of bisphenol A‐bridged polyorganosiloxane precursors and cured to prepare the carbon nanotube/diglycidyl ether of bisphenol A‐bridged polysilsesquioxane (MWCNT/DGEBA‐PSSQ) composites. The molecular motion of MWCNT/DGEBA‐PSSQ nanocomposites was studied by high‐resolution solid‐state ¹³C NMR. Acid‐modification can improve the affinity between MWCNT and the polymer matrix. The molecular motion of the DGEBA‐PSSQ decreased with acid‐modified MWCNT content. However, when unmodified MWCNT was used, the molecular motion of the DGEBA‐PSSQ was increased. SEM and TEM microphotographs confirm that acid‐modified MWCNT exhibits better dispersion than unmodified MWCNT in DGBEA‐PSSQ. The dynamic mechanical properties of acid‐modified MWCNT/DGBEA‐PSSQ composites are more favorable than those of unmodified MWCNT. T_g of the DGEBA‐PSSQ decreased from 174.0 °C (neat DGEBA‐PSSQ) to 159.0 °C (1 wt % unmodified MWCNT) and 156.0 °C (1 wt % acid‐modified MWCNT). The storage modulus (at 30 °C) of the DGEBA‐PSSQ increased from 1.23 × 10⁹ Pa (neat DGEBA‐PSSQ) to 1.65 × 10⁹ Pa (1 wt % acid‐modified MWCNT). However, when unmodified MWCNT was used, the storage modulus of the DGEBA‐PSSQ decreased to 6.88 × 10⁸ Pa (1 wt % unmodified MWCNT). At high temperature, above 150 °C, storage modulus of nanocomposites was higher than that of neat polymer system. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 472–482, 2008     

Surface modification of multiwalled carbon nanotubes via nitroxide‐mediated radical polymerization

The nitroxide‐mediated radical polymerization of styrene was carried out on the surfaces of multiwalled carbon nanotubes (MWNTs) initiated by an MWNT‐supported initiator multiwalled carbon nanotube–2″,2″,6″,6″‐tetramethylpiperidinyloxy (MWNT–Tempo). The content of polystyrene grafted from the surface was controlled by changes in the polymerization conditions, such as the reaction times or the ratios of monomers to initiators. The obtained polystyrene‐grafted multiwalled carbon nanotubes (MWNT–PSs) were further used to initiate the polymerization of 4‐vinylpyridine to get polystyrene‐b‐poly(4‐vinylpyridine)‐grafted multiwalled carbon nanotubes (MWNT–PS‐b‐P4VPs). In contrast to unmodified MWNTs, MWNT–PSs had relatively good dispersibility in various organic solvents, such as tetrahydrofuran, CHCL₃, and o‐dichlorobenzene. The structures and properties of MWNT–PSs and MWNT–PS‐b‐P4VPs were characterized and studied with several methods, including thermogravimetric analysis, Fourier transform infrared, ultraviolet–visible, and transmission electron microscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4656–4667, 2006