Poly(vinyltriethoxysilane) modified MWCNT/polyimide nanocomposites—Preparation,morphological, mechanical,and electrical properties

Multi‐walled carbon nanotube (MWCNT) modified by vinyltriethoxysilane (VTES) via free radical reaction has been prepared (poly (vinyltriethoxysilane) modified MWCNTs, PVTES‐MWCNT). Precursor of polyimide, polyamic acid has been synthesized by reacting 4,4′‐oxydianiline with 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride. PVTES‐MWCNT were then mixed with polyamic acid and heated to 300 °C to form CNT/polyimide composite. During the imidization processes, the silanes on CNT surface reacted with each other and may be connected together by covalent bond (Si? O? Si). The PVTES‐MWCNT was analyzed by Fourier transform infrared and X‐ray photoelectron spectroscopy. The PVTES‐MWCNT/polyimide composites were analyzed by CP/MAS solid state ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. Morphological properties of the PVTES‐MWCNT/polyimide composites were investigated by scanning electron microscope and transmission electron microscope. Electrical conductivity increased dramatically comparing to the unmodified MWCNT/polyimide composites. Mechanical properties of nanocomposite were enhanced significantly by PVTES‐MWCNT. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 803–816, 2008     

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     

Curing kinetics,thermal, mechanical,and dielectric properties based on o‐cresol formaldehyde epoxy resin with polyhedral oligomeric (N‐aminoethyl‐γ‐amino propyl)silsesquioxane

The curing reaction and kinetics of o‐cresol formaldehyde epoxy resin (o‐CFER) with polyhedral oligomeric silsesquioxane of N‐aminoethyl‐γ‐amino propyl group (AEAP‐POSS) were investigated by differential scanning calorimetry (DSC). The thermal, mechanical, and dielectric properties of o‐CFER/AEAP‐POSS nanocomposites were investigated with thermogravimetric analysis (TGA), torsional braid analysis (TBA), tensile tester, impact tester, and electric analyzer, respectively. The results show that the activation energy (E) of curing reaction is 58.08 kJ/mol, and the curing reaction well followed the ?esták‐Berggren (S‐B) autocatalytic model. The glass transition temperature (T_g) increases with the increase in AEAP‐POSS content, and reaches the maximum, 107°C, when the molar ratio (N_s) of amino group to epoxy group is 0.5. The nanocomposites containing a higher percentage of AEAP‐POSS exhibited a higher thermostability. The AEAP‐POSS can effectively increase the mechanical properties of epoxy resin, and the tensile and impact strengths are 2.84 MPa and 143.25 kJ m^?2, respectively, when N_s is 0.5. The dielectric constant (ε), dielectric loss factor (tan δ), volume resistivity (ρ_v), and surface resistivity (ρ_s) are 4.98, 3.11 × 10^?4, 3.17 × 10¹² Ω cm³, and 1.41 × 10¹² Ω cm², respectively, similarly at N_s 0.5. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and applications of novel fluoroalkyl end‐capped oligomers/polyimide/silica nanocomposites

Fluoroalkyl end‐capped acrylic acid, N,N‐dimethylacrylamide, N‐(1,1‐dimethyl‐3‐oxobutyl)acrylamide and vinyltrimethoxysilane oligomers reacted with polyamic acid possessing trimethoxysilyl groups under alkaline conditions to yield the corresponding fluoroalkyl end‐capped oligomers/polyamic acid/silica nanocomposites. These isolated fluorinated composite powders were found to afford nanometer size‐controlled fine particles with a good dispersibility and stability in water and traditional organic solvents. We succeeded in preparing new fluoroalkyl end‐capped oligomers/polyimide/silica nanocomposites by the imidization of fluorinated polyamic acid silica nanocomposites through the stepwise heating at 110 and 270°C under air atmosphere conditions. These fluorinated polyimide/silica nanocomposites thus obtained were applied to the surface modification of glass and poly(methyl methacrylate) (PMMA) to exhibit good hydro‐ and oleo‐phobic characteristics imparted by fluoroalkyl groups in the composites on their surface. In addition, the surface morphology of the modified glass treated with these fluorinated nanocomposites were analyzed by using FE‐SEM and DFM. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrochemical synthesis of polypyrrole/polyimide conducting composite using a polyamic acid precursor

Conducting polymer/poly(amic acid) composites were synthesized by casting poly(amic acid) (PAAc)film onto the surface of stainless steel followed by electrochemical deposition of polypyrrole. Polypyrrole/polyimide (PPy/PI) composites were also formed by preimidizing the polyamic acid film prior to electrodeposition of PPy. The electrical resistance of the bottom side of PPy/PAAc composite (2.3 Ω cm) was lower than that of the PPy/PI composite (6.4 Ω cm), the thickness of the matrix was the same. A PI matrix was used for electropolymerization of pyrrole. The electrodeposition was investigated by using different current densities. IR spectroscopy revealed interactions between the PAAc and PPy in the composite.     

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     

Synthesis,morphology, and properties of hydroxyl terminated‐POSS/polyimide low‐k nanocomposite films

Polyhedral oligomeric silsequioxane (POSS), having eight hydroxyl groups for the preparation of nanocomposites with polyimide (PI) was synthesized by the direct hydrosilylation of allyl alcohol with octasilsesquioxane (Q₈M₈^H) with platinum divinyltetramethyl disiloxane Pt(dvs) as a catalyst. The structure of allyl alcohol terminated‐POSS (POSS‐OH) was confirmed by FTIR, NMR, and XRD. A high performance, low‐k PI nanocomposite from pyromellitic dianhydride (PMDA)‐4,4'‐oxydianiline (ODA) polyamic acid cured with POSS‐OH was also successfully synthesized. The incorporation of POSS‐OH into PI matrix reduced dielectric constant of PI without loosing mechanical properties. Furthermore, the effects of POSS‐OH on the morphology and properties of the PI/POSS‐OH nanocomposites were investigated using UV–vis, FTIR, XRD, SEM, AFM, transmission electron microscope (TEM), TGA, and contact angle. The homogeneous dispersion of POSS particles was confirmed by SEM, AFM, and TEM. The nanoindentation showed that the modulus increased upon increasing the concentration of POSS‐OH in PI, whereas the hardness did not increase very much with respect to loading of POSS, due to soft‐interphase around POSS molecules in the resulting nanocomposites. Overall results demonstrated the nanometer‐level integration of the polymer and POSS‐OH. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5887–5896, 2008     

Uncross‐linked polypropylene (PP)/ethylene‐propylene‐diene (EPDM)/multi walled carbon nanotube (MWCNT) and dynamically vulcanized PP/EPDM/MWCNT nanocomposites

In this study, relatively large amounts of polypropylene (PP), ethylene‐propylene‐diene (EPDM), and multi‐walled carbon nanotube (MWCNT) were melt‐mixed with and without DCP. Dynamically vulcanized PP/EPDM (TPV)/MWCNT nanocomposites were prepared by two methods: the MWCNTs were added either before or after the dynamic vulcanization of the blends. The effects of composition, rotor speed, and dynamic vulcanization on their surface resistivity were investigated. The surface resistivity of uncross‐linked PP/EPDM/MWCNT nanocomposites increases with increasing the content of EPDM. At PP/EPDM (70/30 wt%) nanocomposite with 1.5 phr MWCNT, slightly lower surface resistivity is obtained by increasing the rotor speed during mixing. However, for PP/EPDM (50/50 wt%) and PP/EPDM (30/70 wt%) nanocomposites, surface resistivity decreases with increasing the rotor speed from 30 to 60 rpm. But further increase in rotor speed (90 rpm) leads to an increase of surface resistivity. When the MWCNTs were added after the dynamic vulcanization of the blends, the surface resistivity of TPV70/MWCNTnanocomposite is lower than that of uncross‐linked PP/EPDM/MWCNT nanocomposite. However, when the MWCNTs were added before the dynamic vulcanization of the blends, the surface resistivity of TPV70/MWCNT nanocomposite is >10¹² Ω/square. Copyright © 2010 John Wiley & Sons, Ltd.     

Characterization of cobalt-modified polyimides

Modified polyimide films containing cobalt have been prepared by the addition of cobalt(II) chloride to a solution containing one of the diamines 4,4′-oxydianiline (ODA) or 4,4′-diaminodiphenylsulfide (DDS) and one of the dianhydrides 3.3′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA) or 4,4′-bis(3,4-dicarboxyphenoxy)diphenylsulfide dianhydride (BDSDA) and characterized by thermal methods, UV-visible spectra, room-temperature direct-current electrical resistivity measurements, and X-ray photoelectron and Auger electron spectroscopy. A principal goal of this work was to establish if there was coordination of the potential donor atoms of the polymide to cobalt. UV-visible spectra of the modified polyamic acid solutions and polyimide films and a titration study of a model system do not show any appreciable coordination with either the polyamic acid or the polyimide; rather, the cobalt(II) appears to be coordinated to the solvent, N,N-dimethylacetamide (DMAc), as [Co(DMAc)₄]²⁺, until the temperature is raised above 200°C. X-ray photoelectron spectra of films cured only to 200°C also do not show significant shifts in the binding energies of the potential donor atoms from those binding energies of the undoped polymers, confirming little direct coordination of the cobalt to atoms of the polyimide. Heating the films to 300°C in a forced-air oven causes the formation of a cobalt oxide layer on the air side of the polymer. Direct-current electrical resistivity measurements on this surface show a 10⁴–10⁶ reduction in resistivity due to this layer.     

Synthesis and Electronic/ionic Transport Properties of MoO2/rGO Anode for Lithium Ion Batteries

MoO₂/rGO (reduced graphite oxide) composites have been synthesized by hydrothermal method followed by anneal and characterized by X‐ray diffraction (XRD) and scanning electron microscope (SEM). Galvanostatic charge/discharge testing and electrochemical impedance spectroscopy (EIS) techniques are employed to evaluate the kinetic behaviors of the MoO₂/rGO during lithiation/delithiation. The obtained MoO₂‐based materials have monoclinic crystal structure, and worm like shape with average dimensions of 100‐200 nm width and 500 nm‐1 μm length. There are two steps of lithium ion intercalation/de‐intercalation for the MoO₂/rGO anode at the potential ranging from 1.0 to 3.5 V, locating at E_Li/Li⁺ = 1.60/1.75 V, 1.25/1.40 V, and the first discharge and charge capacities are, respectively, 221.0 and 185.4 mAh g^?1. The resistances of R_SEI and R_CT for the MoO₂/rGO anode are 2‐4 Ω and below 5 Ω. Moreover, the lithium diffusion coefficient calculated from the EIS measurement is about 3.6×10^?9 cm² s^?1.     

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     

Rutherford backscattering spectrometry studies of iodine diffusion in polyimide

Rutherford backscattering spectrometry with a 2.1-meV He²⁺ion beam is used to measure the diffusion of iodine into polyamic acid and polyimide films. The iodine diffusion coefficient D decreases from its initial value of about 2X10^?13cm²/s in polyamic acid to approximately 1.4 × 10^?15cm²/s in partially cured polyimide, but then increases to a value of nearly 1.5 × 10^?14 cm²/s in fully cured polyimide. This dramatic increase in D cannot be attributed to the “in-plane” biaxial orientation of the polyimide molecules since indential D's were found with isotropic specimens. Microvoids less than 2 nm in size caused by water and carbon dioxide formation during imidization may, however, give rise to the observed behavior. The results demonstrate that Rutherford backscattering spectrometry with its excellent depth resolution (better than 30 nm) and good sensitivity (50 ppm iodine can be detected) is very useful for measuring the diffusion of slowly diffusing species in glassy polymers.     

Electrochemical Sensor Prepared from Molecularly Imprinted Polymer for Recognition of 1,3-Dinitrobenzene (DNB)

An electrochemical sensor was modified with multi‐wall carbon nanotubes (MWCNT) and molecularly imprinted polymer (MIP) material synthesized with acrylamide and ethylene glycol dimethacrylate (EGDMA) in the presence of 1,3‐dinitrobenzene (DNB) as the template molecule. The MWCNT and MIP layers were successively modified on the surface of a glassy carbon electrode (GCE), of which the MIP film works as an artificial receptor due to its specific molecular recognition sites. The MIP material was characterized by FT‐IR and electrochemical methods of square wave voltammetry (SWV). The interferences of other nitroaromatic compounds (NAC) such as 2,4,6‐trinitrotoluene (TNT), 1,3,5‐trinitrobenzene (TNB) and 2,4‐dinitrotoluene (DNT) to DNB were also investigated by the prepared MIP/MWCNT electrode. Compared with other traditional sensors, the MIP/MWCNT modified electrode shows good selectivity and sensitivity. In addition, the current responses to DNB are linear with the concentration ranging from 4.5×10^?8 to 8.5×10^?6 mol/L with the detection limits of 2.5×10^?8 (?0.58 V) and 1.5×10^?8 mol/L (?0.69 V) (S/N=3). The construction process of MIP/MWCNT modified electrode was also studied as well. All results indicate that the MIP/MWCNT modified electrode established an improving way for simple, fast and selective analysis of DNB.     

Highly soluble conducting poly(ethylene oxide) grafted at two sites of poly(o‐aminobenzyl alcohol)

Poly(o‐aminobenzyl alcohol) (POABA) was grafted with poly(ethylene oxide)s (PEOs) through the reaction of tosylated PEO with both the hydroxide and amine moieties of reduced POABA. Reduced POABA was prepared through the acid‐mediated polymerization of o‐aminobenzyl alcohol, followed by neutralization with an aqueous ammonium hydroxide solution and reduction with hydrazine. The grafted copolymers were very soluble in common polar solvents, such as chloroform, tetrahydrofuran, and dimethylformamide, and the copolymers with longer PEO side chains (number‐average molecular weight > 164) were even water‐soluble. The conductivities of the doped grafted copolymers decreased with increasing PEO side‐chain length because of the nonconducting PEO and its torsional effect on the POABA backbone. The conductivity of highly water‐soluble POABA‐g‐PEO‐350 was 0.689 × 10^?3 S/cm, that is, in the semiconducting range. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4756–4764, 2004     

Preparation and characterization of a polyimide nanofoam through grafting of labile poly(propylene glycol) oligomer

Preparation of a polyimide nanofoam (PI‐F) for microelectronic applications was carried out using a polyimide precursor synthesized from poly[(amic acid)‐co‐(amic ester)] and grafted with a labile poly(propylene glycol) (PPG) oligomer. Polyimide precursor was synthesized by partial esterification of poly(amic acid) (PAA) derived from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA). The precursor was then grafted with bromide‐terminated poly(propylene glycol) in the presence of K₂CO₃ in hexamethylphosphoramide and N‐methylpyrrolidone, imidized at 200°C in nitrogen and the product was subsequently decomposed in air at 300°C to eliminate the labile PPG oligomer to produce PMDA/ODA polyimide nanofoam. Nuclear magnetic resonance spectroscopy (¹H‐NMR) and Fourier transform infrared spectroscopy (FT‐IR) techniques were used to characterize the formation of polyimide precursor and extent of grafting of PPG with polyimide. The results of thermogravimetric analysis (TGA) showed three step decomposition of nanofoam with the removal of PPG at 350°C and decomposition of polyimide at around 600°C. The polyimide nanofoams were also characterized by small angle X‐ray scattering (SAXS), field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM). The morphology showed nanophase‐separated structures with uniformly distributed and non‐interconnected pores of 20–40 nm in size. Dynamic mechanical analysis (DMA) indicated higher storage modulus for the foamed structure compared to the pure PI with reduction in loss tangent for the former system. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis,Characterization, Electronic and Gas‐Sensing Properties towards H2 and CO of Transparent,Large‐Area,Low‐Layer Graphene

Low‐layered, transparent graphene is accessible by a chemical vapor deposition (CVD) technique on a Ni‐catalyst layer, which is deposited on a <100> silicon substrate. The number of graphene layers on the substrate is controlled by the grain boundaries in the Ni‐catalyst layer and can be studied by micro Raman analysis. Electrical studies showed a sheet resistance (R_sheet) of approximately 1435 Ω per □, a contact resistance (R_c) of about 127 Ω, and a specific contact resistance (R_sc) of approximately 2.8×10^?4 Ω cm² for the CVD graphene samples. Transistor output characteristics for the graphene sample demonstrated linear current/voltage behavior. A current versus voltage (I_ds–V_ds) plot clearly indicates a p‐conducting characteristic of the synthesized graphene. Gas‐sensor measurements revealed a high sensor activity of the low‐layer graphene material towards H₂ and CO. At 300 °C, a sensor response of approximately 29 towards low H₂ concentrations (1 vol %) was observed, which is by a factor of four higher than recently reported.     

Electrical,Optical, and Structural Properties of SnO2: F Films as a Function of Fluoride Precursor Concentration and Temperature

Atmospheric pressure chemical vapor deposition (APCVD) employing the precursor system of tin tetrachloride, ethyl formate, and 2,2,2‐trifluoroethyl trifluoroacetate vapors that were transported to hot glass substrates to deposit fluorine doped tin dioxide thin films. The system is optimized with respect to the substrate deposition temperature and to the amount of fluoride added to the precursor stream and the resultant structural, electrical and optical properties compared. Increasing the substrate temperature from 360 °C to 610 °C resulted in an approximately linear increase in thickness of the tin dioxide films. However, the resistivity decreased from 1.8 × 10^–2 Ω · cm at 360 °C to a minimum of 5.9 × 10^–4 Ω · cm at 560 °C and increased to 9.4 × 10^–4 Ω · cm at 610 °C. While maintaining a substrate temperature of 560 °C different amounts of fluorine precursor was introduced into the carrier stream, from 0 mL · h^–1 to 5 mL · h^–1, resulting in a decrease in resistivity (ρ) from 5.3 × 10^–2 Ω · cm at 0 mL · h^–1 to a minimum of 5.9 × 10^–4 Ω · cm at 2 mL · h^–1 and then increased to 1.0 × 10^–3 Ω · cm at 5 mL · h^–1. As the amount of fluoride is increased a concommittent increase in carrier concentration results until the point of overdoping the film produces an increase in scattering sites that increases resistivity. Best films were deposited at 560 °C and when the fluoride precursor flow rate was 2 mL · h^–1.     

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     

Characterization and Electrocatalytic Activity of Nanocomposites Consisting of Nanosized Cobalt Tetraaminophenoxy Phthalocyanine,Multi‐walled Carbon Nanotubes and Gold Nanoparticles

Glassy carbon electrodes were modified with composites containing cobalt tetraaminophenoxy phthalocyanine nanoparticles (CoTAPhPc NP ), multi‐walled carbon nanotubes (MWCNT) and gold nanorods (AuNRs). The modified electrodes were studied for their electrocatalytic behavior towards the reduction of hydrogen peroxide. Phthalocyanine nanoparticles significantly improved electron transfer kinetics as compared to phthalocyanines which are not in the nanoparticle form when alone or in the presence of multiwalled carbon nanotubes (MWCNTs). CoTAPhPc NP ‐MWCNT‐GCE proved to be suitable for hydrogen peroxide detection with a catalytic rate constant of 3.45×10³ M^?1 s^?1 and a detection limit of 1.61×10^?7 M. Adsorption Gibbs free energy ΔG^o was found to be ?19.22 kJ mol^?1 for CoTAPhPc NP ‐MWCNT‐GCE.     

Polyimide/polyoxometalate copolymer thin films: synthesis,thermal and dielectric properties

A mono‐lancunary keggin‐type decatungstosilicate (SiW₁₁) polyoxometalate (POM) modified by γ‐aminopropyltriethoxysilane (KH550) was incorporated into polyimide (PI) through copolymerization. Nuclear magnetic resonance (NMR), fourier transition infrared spectroscopy (FTIR), and wide angle X‐ray diffraction (WAXD) were used to characterize the structure and composition of the polyoxometalate–organosilane hybrid (SiW₁₁KH550) and PI/SiW₁₁KH550 copolymers. The differential scanning calorimetry (DSC) studies indicate that the glass transition temperature (T_g) of PI/SiW₁₁KH550 copolymers increases from 330°C (for neat PI) to 409°C (for the copolymer sample with 10 wt% of SiW₁₁KH550). Dielectric measurement showed that both the dielectric constant and the dielectric loss for the copolymer thin films decreased with the increase in SiW₁₁KH550 content, and the dielectric constant and dielectric loss values decreased to 2.1 and 3.54 × 10^?3, respectively, for the copolymer sample with 10 wt% of SiW₁₁KH550. The incorporation of SiW₁₁KH550 into polymer matrices is a promising approach to prepare PI films with a low dielectric constant and low dielectric loss. Copyright © 2009 John Wiley & Sons, Ltd.