Semiconductive bionanocomposites of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) and MWCNTs for neural growth applications

Bionanocomposites of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (P3HB3HHx) (13 % by mol of HHx) with multiwalled carbon nanotubes (MWCNTs) were prepared to obtain semiconductive nanocomposites for potential applications as scaffolds for nerve repair. The effect of the polymer/nanotube interface on the composite properties was studied using oxidized (oxi‐MWCNTs) and surface modified MWCNTs with low‐molecular weight P3HB3HHx (pol‐MWCNTs), in a ratio from 0.3 to 1.2 wt % for each type of MWCNTs employed. Morphology and conductive properties of the composites indicated a good interaction between pol‐MWCNTs and the polymer matrix. Composites with improved conductivity were obtained with only 0.3 wt % of pol‐MWCNTs added. However, agglomeration and lower conductivity was observed for samples with oxi‐MWCNTs. Cell viability studies carried out with neurospheres showed that samples with 1.2 wt % of pol‐MWCNTs are not cytotoxic and, in addition favors the neurospheres growth on the composite surface. Considering the electrical properties and biological behavior, nanocomposites of P3HB3HHx and pol‐MWCNTs are promising substrates for the regeneration of nerve tissue. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 349–360     

Copolymer networks from carboxyl‐containing polyaryletherketone and diglycidyl ether of bisphenol‐A: Preparation and properties

This article presents a new type of epoxy‐toughening system, in which high‐T_g polyaryletherketone (PEK‐L) containing one carboxyl group per repeating unit was utilized to randomly copolymerize with epoxy resin (DGEBA) to form crosslinking network. Compared to the neat epoxy resin, the PEK‐L/DGEBA copolymers showed simultaneous enhancement in flexural strains at break by 282%, G_IC value by 193%, and flexural strength by 14%. The reason was attributed to the uniform three‐dimensional copolymer network interweaved by PEK‐L and DGEBA segments through strong covalent bonds. The copolymerization process were monitored and examined by FTIR spectra. The effect of copolymer composition on the thermal and mechanical properties as well as toughening mechanism were also investigated and discussed in detail. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Synthesis of MWCNTs‐core/thiophene polymer‐sheath composite nanocables by a cationic surfactant‐assisted chemical oxidative polymerization and their structural properties

Multi‐walled carbon nanotubes (MWCNTs)‐core/thiophene polymer‐sheath composite nanocables were synthesized by chemical oxidative polymerization of 3,4‐ethylenedioxythiophene (EDOT) with oxidant (FeCl₃) in the presence of cationic surfactant, deceyltrimethyl ammonium bromide (DTAB). In the polymerization process, DTAB surfactant molecules were adsorbed on the surface of MWCNTs and forms MWCNTs‐DTAB soft template. Upon the addition of EDOT and oxidant, the polymerization take place on the surface of MWCNTs and PEDOT is gradually deposited on the surface of MWCNTs. The resulting MWCNTs‐PEDOT nanocomposites have the nanocable structure. Nanocomposites were characterized by HRTEM, FE‐SEM, XRD, XPS, TGA, FTIR and PL, respectively. The π‐π interactions between PEDOT and MWCNTs enhancing the thermal and electrical properties of the nanocomposites with loading of MWCNTs. The temperature dependence conductivity measurements show that the conductivity of the nanocomposite decrease with a decrease of temperature, and conductivity‐temperature relationship is well fit by the quasi‐one dimensional variable range hopping mode. The mechanism for the formation of composite nanocables was explained on the basis of self‐ assembly of micelles. The reported self‐assembly strategy for the synthesis of PEDOT‐coated MWCNTs in micellar medium is a rapid, versatile, potentially scalable, stable, and making it useful for further exploitation in a varies types of applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1477–1484, 2010     

Decoration of Fe3O4 nanoparticles on the surface of poly(acrylic acid) functionalized multi‐walled carbon nanotubes by covalent bonding

Fe₃O₄ nanoparticles were indirectly implanted onto functionalized multi‐walled carbon nanotubes (MWCNTs) leading to a nanocomposite with stronger magnetic performance. Poly(acrylic acid) (PAA) oligomer was first reacted with hydroxyl‐functionalized MWCNTs (MWCNTs‐OH) forming PAA‐grafted MWCNTs (PAA‐g‐MWCNTs). Subsequently, Fe₃O₄ nanoparticles were attached onto the surface of PAA‐g‐MWCNTs through an amidation reaction between the amino groups on the surface of Fe₃O₄ nanoparticles and the carboxyl groups of PAA. Fourier transform infrared spectra confirmed that the Fe₃O₄ nanoparticles and PAA‐g‐MWCNTs were indeed chemically linked. The morphology of the nanocomposites was characterized using transmission electron microscope (TEM). The surface and bulk structure of the nanocomposites were examined using X‐ray diffraction, X‐ray photoelectron spectrometer (XPS), and thermogravimetric analysis (TGA). The magnetic performance was characterized by vibrating sample magnetometer (VSM) and the magnetic saturation value of the magnetic nanocomposites was 47 emu g^?1. The resulting products could be separated from deionized water under an external magnetic field within about 15 s. Finally, the magnetorheological (MR) performances of the synthesized magnetic nanocomposites and pure Fe₃O₄ nanoparticles were examined using a rotational rheometer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Covalent bonded polymer–graphene nanocomposites

This report describes a new route to covalently bonded polymer–graphene nanocomposites and the subsequent enhancement in thermal and mechanical properties of the resultant nanocomposites. At first, the graphite is oxidized by the modified Hummers method followed by functionalization with Octadecylamine (ODA). The ODA functionalized graphite oxides are reacted with methacryloyl chloride to incorporate polymerizable ? C?C? functionality at the nanographene platelet surfaces, which were subsequently employed in in situ polymerization of methylmethacrylate to obtain covalently bonded poly(methyl methacrylate) (PMMA)–graphene nanocomposites. The obtained nanocomposites show significant enhancement in thermal and mechanical properties compared with neat PMMA. Thus, even with 0.5 wt % graphene nanosheets, the T_g increased from 119 °C for neat PMMA to 131 °C for PMMA–graphene nanocomposite, and the respective storage modulus increased from 1.29 to 2 GPa. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4262–4267, 2010     

Dissolution of MWCNTs by using polyoxadiazoles,and highly effective reinforcement of their composite films

Nonmodified multiwalled carbon nanotubes (MWCNTs)/sulfonated polyoxadiazole (sPOD) nanocomposites are successfully prepared by a facile solution route. The pristine MWCNTs are dispersed in a sPOD solution, and the mixtures are fabricated into thin films by solution casting. The homogeneous dispersion of nanotubes in the composites is confirmed by transmission electron microscopy. The mechanical properties, thermal stability, and electrical conductivity are investigated. Tensile strength, elongation at break, and tensile energy to break are shown to increase by more than 28, 45, and 73%, respectively, by incorporating up to 1.0 wt % pristine MWCNTs. The experimental values for sPOD/MWCNTs composite stiffness are compared with Halpin‐Tsai and modified Halpin‐Tsai predictions. The storage modulus is found to increase up to 10% at low CNT loading. The composite films, which have an outstanding thermal stability, show an increase of up to 57 °C in the initial degradation temperature. The addition of 1.0 wt % MWCNTs increases the electrical conductivity of the sPOD matrix by two orders of magnitude. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Covalent surface functionalization of multiwalled carbon nanotubes through bergman cyclization of enediyne‐containing dendrimers

A method for covalent functionalization of multiwalled carbon nanotubes (MWCNTs) was developed using the free radicals generated through Bergman cyclization of enediyne‐containing compounds. Four enediyne‐bearing Frechet type dendrimers were synthesized in good quantities and characterized. Then, the enediyne‐containing molecules were reacted with MWCNTs in N‐methyl‐2‐pyrrolidinone at 206 °C under nitrogen. The structure and morphology of the resulting products were characterized by thermogravimetric analysis, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy. The dendrimer‐functionalized MWCNTs showed good solubility/dispersibility in common organic solvents and polymer solutions. They were used in the formation of polymer composites through electrospinning with polycaprolactone. The results confirmed the surface functionalization of MWCNTs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

The mechanical and electrical properties of carbon nanotube‐grafted polyimide nanocomposites

Polyimide (PI)‐based nanocomposites containing aminophenyl functionalized multiwalled carbon nanotubes (AP‐MWCNTs) obtained through a diazonium salt reaction was successfully prepared by in situ polymerization. PI composites with different loadings of AP‐MWCNTs were fabricated by the thermal conversion of poly(amic acid) (PAA)/AP‐MWCNTs. The mechanical and electrical properties of the AP‐MWCNTs/PI composites were improved compared with those of pure PI due to the homogeneous dispersion of AP‐MWCNTs and the strong interfacial covalent bonds between AP‐MWNTs and the PI matrix. The conductivity of AP‐MWNTs/PI composites (5:95 w/w) was 9.32 × 10^?1 S/cm which was about 10¹⁵ times higher than that of Pure PI. The tensile strength and tensile modules of the AP‐MWCNTs/PI composites with 0.5 wt % of AP‐MWCNTs were increased by about 77% (316.9 ± 10.5 MPa) and 25% (8.30 ± 1.10 GPa) compared to those of pure PI, respectively. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 960–966     

Waterborne polyurethane nanocomposites having shape memory effects

UV curable waterborne polyurethane/silica nanocomposites were designed and synthesized with functionalized silicas, where the functionalization was made with allyl isocyanate. The incorporated silica particles gave triple effects of multifunctional chemical cross‐links, reinforcing fillers, and stress relaxation retarders. Consequently, functionalized silica incorporated into the polymer chains showed significantly improved mechanical and thermal properties than the simple addition of unmodified silica. Notably, over 99% shape fixity and shape recovery with minimum cyclic hysteresis were obtained for the repeated cycles at 1% loading of the modified silica. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of interaction between poly(ethylene terephthalate) and carbon nanotubes on the morphology and properties of their nanocomposites

Poly(ethylene terephthalate) (PET) nanocomposites were prepared by melt‐extruding mixtures of PET and functionalized multiwalled carbon nanotubes (MWNTs) with some interaction with PET molecules. For the functionalization of MWNTs, benzyl isocyanate and phenyl isocyanate with different molecular flexibility were employed on the surface of the MWNTs via chemical modification, respectively. The reaction for functionalization of MWNTs was confirmed by FTIR and transmission electron microscopy (TEM) measurements. TEM observations indicated that both benzyl and phenyl isocyanate groups covered the surface of the MWNTs after functionalization. The PET nanocomposites containing isocyanate groups showed improved mechanical properties, including the tensile strength and tensile modulus, compared with those with pristine and acid‐treated nanotubes. These improvements were ascribed to π–π interactions between the aromatic rings of PET molecules and the isocyanate group in MWNTs. The functionalized MWNTs showed a better dispersion of carbon nanotubes in the matrix polymer and a different fractured cross‐section morphology in scanning electron microscope measurements relative to the pristine MWNTs. The crystallinity of the functionalized MWNT‐PET nanocomposites was significantly higher than that of the pristine and acid‐treated MWNTs. FTIR results indicated that the presence of carbon nanotubes induced trans‐conformation of PET chains, and trans conformation was particularly dominant in PET composites incorporating MWNT‐phenyl. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 900–910, 2008     

Melt‐crystallization mechanism of poly(ethylene terephthalate)/multi‐walled carbon nanotubes prepared by in situ polymerization

A series of poly(ethylene terephthalate)/multi‐walled carbon nanotubes (PET/MWCNTs) nanocomposites were prepared by in situ polymerization using different amounts of multi‐walled carbon nanotubes (MWCNTs). The polymerization of poly(ethylene terephthalate) (PET) was carried out by the two‐stage melt polycondensation method. The intrinsic viscosity (IV) of the composites is ranged between 0.31 and 0.63 dL/g depending on the concentration of the MWCNTs. A decrease of IV was found by increasing MWCNTs content. This is due to the reactions taking place between the two components leading to branched and crosslinked macromolecules. These reactions are, mainly, responsible for thermal behavior of nanocomposites. The melting point of the nanocomposites was shifted to slightly higher temperatures by the addition till 0.55 wt % of MWCNTs while for higher concentration was reduced. The degree of crystallinity in all nanocomposites was, also, reduced by increasing MWCNTs amount. However, from crystallization temperature, it was found that MWCNTs till 1 wt % can enhance the crystallization rate of PET, whereas at higher content (2 wt %), the trend is the opposite due to the formation of crosslinked macromolecules. From the extended crystallization analysis, it was proved that MWCNTs act as nucleating agents for PET crystallization. Additionally, the crystallization mechanism due to the existence of MWCNT becomes more complicated because two mechanisms with different activation energies are taking place in the different degrees of crystallization, depending on the percentage of MWCNT. The effect of molecular weight also plays an important role. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1452–1466, 2009     

Preparation of modified multi‐walled carbon nanotubes as a reinforcement for epoxy shape‐memory polymer composites

Effectively improving the mechanical properties and thermal resistance of epoxy shape‐memory polymers (ESMPs) without affecting their shape‐memory performance is necessary to expand these polymers in practical applications. In this article, modified multi‐walled carbon nanotubes (MWCNTs) were prepared and used as efficient reinforcement for enhancing the comprehensive properties of ESMPs. Increases of nearly 289% to 444% for impact strength and 112% to 184% for tensile force were obtained by adding only 0.1 to 1 wt% epoxy‐modified MWCNTs. The addition of unmodified and carboxyl‐modified MWCNTs was also investigated but showed less impact on the mechanical properties of the ESMPs than epoxy‐modified MWCNTs. Thermogravimetry analysis (TGA) and dynamic mechanical analyses (DMA) showed that less than 1 wt% modified MWCNTs can enhance the heat resistance of ESMPs greatly. Although the shape recovery time for composite materials increased upon adding the MWCNTs, the entire recovery time was still less than 1 minute, and the shape recovery rate was relatively high, nearly 100%.     

碳纳米管改性环氧树脂的导热和阻燃性能

以双酚A二缩水甘油醚(DGEBA)环氧树脂(Epoxy Resin,EP)为基体、甲基六氢苯酐(MHHPA)为固化剂、以多壁碳纳米管(MWCNTs)为添加剂制备了环氧树脂/碳纳米管纳米复合材料。通过对微观结构、玻璃化转变温度(Tg)、热失重、热导率和锥形量热测试结果分析,研究了质量分数少于1.5%的MWCNTs对环氧树脂的导热和阻燃性能影响,结果表明,MWCNTs质量分数为1.5%时,复合材料发生团聚;纳米复合材料随着MWCNTs质量分数的增加Tg值先增加后降低;失重5%时,对应的温度先增加后降低,残炭量增加;样品的热导率呈现先升高后降低的趋势,当MWCNTs质量分数为1%时,复合材料的热导率最大;MWCNTs加入后环氧树脂的总释热量减少,释烟量增加,阻燃性得到一定程度的提高。     

Click coupled graphene for fabrication of high‐performance polymer nanocomposites

An effective technique of using click coupled graphene to obtain high‐performance polymer nanocomposites is presented. Poly(ε‐caprolactone) (PCL)‐click coupled graphene sheet (GS) reinforcing fillers are synthesized by the covalent functionalization of graphene oxide with PCL, and subsequently the PCL‐GS as a reinforcing filler was incorporated into a shape memory polyurethane matrix by solution casting. The PCL‐click coupled GS has shown excellent interaction with the polyurethane matrix, and as a consequence, the mechanical properties, thermal stability, thermal conductivity, and thermo‐responsive shape memory properties of the resulting nanocomposite films could be enhanced remarkably. In particular, for polyurethane nanocomposites incorporated with 2% PCL‐GS, the breaking stress, Young's modulus, elongation‐at‐break, and thermal stability have been improved by 109%, 158%, 28%, and 71 °C, respectively. This click coupling protocol offers the possibility to fully combine the extraordinary performance of GSs with the properties of polyurethane. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Exploitation of introducing of catalytic centers into layer galleries of layered silicates and related epoxy nanocomposites. I. Epoxy nanocomposites derived from montmorillonite modified with catalytic surfactant‐bearing carboxyl groups

Montmorillonite (MMT) was modified with the acidified cocamidopropyl betaine (CAB) and the resulting organo‐montmorillonite (O‐MMT) was dispersed in an epoxy/methyl tetrahydrophthalic anhydride system to form epoxy nanocomposites. The intercalation and exfoliation behavior of the epoxy nanocomposites were examined by X‐ray diffraction and transmission electron microscopy. The curing behavior and thermal property were investigated by in situ Fourier transform infrared spectroscopy and DSC, respectively. The results showed that MMT could be highly intercalated by acidified CAB, and O‐MMT could be easily dispersed in epoxy resin to form intercalated/exfoliated epoxy nanocomposites. When the O‐MMT loading was lower than 8 phr (relative to 100 phr resin), exfoliated nanocomposites were achieved. The glass‐transition temperatures (T_g's) of the exfoliated nanocomposite were 20 °C higher than that of the neat resin. At higher O‐MMT loading, partial exfoliation was achieved, and those samples possessed moderately higher T_g's as compared with the neat resin. O‐MMT showed an obviously catalytic nature toward the curing of epoxy resin. The curing rate of the epoxy compound increased with O‐MMT loading. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1192–1198, 2004     

Synthesis and characterization of pyrene bearing amphiphilic miktoarm star polymer and its noncovalent interactions with multiwalled carbon nanotubes

A novel amphiphilic miktoarm star polymer, polystyrene‐poly(ethylene glycol)‐poly(methyl methacrylate), bearing a pyrene group at the end of PS arm (Pyrene‐PS‐PEG‐PMMA) was successfully synthesized via combination of atom transfer radical polymerization and click chemistry. The structure and composition of the amphiphilic miktoarm star polymer were characterized by gel permeation chromatography and ¹H NMR. The functionalization of multiwalled carbon nanotubes (MWCNTs) via “π–π” stacking interactions with pyrene‐PS‐PEG‐PMMA miktoarm star polymer was accomplished and the resulting polymer‐MWCNTs hybrid was analyzed by using ¹H NMR, UV–vis, fluorescence spectroscopy, and thermal gravimetric analysis. The high‐resolution transmission electron microscopy and analytical techniques aforementioned confirmed that the noncovalent functionalization of MWCNT's with the amphiphilic miktoarm star polymer was successfully achieved. The MWCNT/pyrene‐PS‐PEG‐PMMA exhibited significant dispersion stability in common organic solvents such as dimethyl formamide, chloroform, and tetrahydrofuran. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Viscoelasticity and thermal stability of polylactide composites with various functionalized carbon nanotubes

Polylactide (PLA) nanocomposites containing various functionalized multi-walled carbon nanotubes (MWCNTs) were prepared directly by melt compounding. The linear rheology and thermal stability of the PLA nanocomposites were, respectively, investigated by the parallel plate rheometer and TGA, aiming at examining the effect of surface functionalization on the dispersion of MWCNTs by using viscoelastic and thermal properties. Among three MWCNTs used in this work, the carboxylic MWCNTs present better dispersion in PLA matrix than the hydroxy and purified MWCNTs because the corresponding composite shows the lowest rheological percolation threshold, which is further confirmed by the TEM and solution experiments. The presence of all these three MWCNTs, however, nearly cannot improve the thermal stability effectively at the initial stage of degradation and the temperature corresponding to a weight loss of 5 wt% (T_5 wt%) only shows slight increase in contrast to that of the neat PLA while with increase of decomposition level, the presence of carboxylic and purified MWCNTs retards the depolymerization of PLA evidently, showing remarkable increase in the temperature corresponding to maximum rate of decomposition (T_max). Both the dispersion state and the surface functionalization of MWCNTs are very important to the thermal stability of PLA matrix.     

SYNTHESIS, CHARACTERIZATION AND PROPERTIES OF ORGANOCLAY-MODIFIED POLYSULFONE/EPOXY INTERPENETRATING POLYMER NETWORK NANOCOMPOSITES

Organoclay-modified hydroxylterminated polysulfone (PSF)/epoxy interpenetrating network nanocomposites (oM-PSF/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polysulfone and epoxy resin (PSF/EP) using diaminodiphenylmethane (DDM) as curing agent.The mechanical properties like tensile strength,tensile modulus,flexural strength,flexural modulus and impact properties of the nanocomposites were studied as per ASTM standards.Differ...     

Effects of processing conditions on rheological,thermal, and electrical properties of multiwall carbon nanotube/epoxy resin composites

We report on the effect of processing conditions on rheology, thermal and electrical properties of nanocomposites containing 0.02–0.3 wt % multiwall carbon nanotubes in an epoxy resin. The influence of the sonication, the surface functionalization during mixing, as well as the application of external magnetic field (EMF) throughout the curing process was examined. Rheological tests combined with optical microscopy visualization are proved as a very useful methodology to determine the optimal processing conditions for the preparation of the nanocomposites. The Raman spectra provide evidence for more pronounced effect on the functionalized with hardener compositions, particularly by curing upon application of EMF. Different chain morphology of CNTs is created depending of the preparation conditions, which induced different effects on the thermal and electrical properties of the nanocomposites. The thermal degradation peak is significantly shifted towards higher temperatures by increasing the nanotube content, this confirming that even the small amount of carbon nanotubes produces a strong barrier effect for the volatile products during the degradation. The ac conductivity measurements revealed lower values of the percolation threshold (pc) in the range of 0.03–0.05 wt %. CNTs for the nanocomposites produced by preliminary dispersing of nanotubes in the epoxy resin, compared to those prepared by preliminary functionalization of the nanotubes in the amine hardener. This is attributed to the higher viscosity and stronger interfacial interactions of the amine hardener/CNT dispersion which restricts the reorganization of the nanotubes. The application of the EMF does not influence the pc value but the dc conductivity values (σ_dc) of the nanocomposites increased at about one order of magnitude due to the development of the aforementioned chain structure. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011