Emulsion Polymerization Pathway for Preparation of Polyaniline‐Sulfate Salt,using Non Ionic Surfactant

In this work, aniline was polymerized directly to the polyaniline‐sulfate salt without using a protonic acid. The polyaniline‐sulfate salt was prepared by emulsion polymerization, using a non ionic surfactant such as poly(ethylene glycol)–block poly(propylene glycol)‐block poly(ethylene glycol). In the aniline oxidation process, to give the polyaniline salt by ammonium persulfate, the sulfate ion is generated from ammonium persulfate and doped on to the polyaniline. Ammonium persulfate acts both as an oxidizing agent, as well as the protonating agent in the aniline polymerization process, to give the polyaniline salt. This result indicates that the effect of sulfate ion, generated by ammonium persulfate during oxidation of aniline to the polyaniline salt, may be taken into consideration in the polymerization process of aniline.     

Polyaniline‐coupled graphene/nickel hydroxide nanohybrids as flame retardant and smoke suppressant for epoxy composites

Graphene‐polyaniline/nickel hydroxide ternary hybrid (RGO‐PANI/Ni(OH)₂) was synthesized and incorporated into epoxy resin (EP) to improve the fire retardant property. Thermogravimetric analysis results showed that the RGO‐PANI/Ni(OH)₂ nanohybrid could catalyze the thermal degradation of epoxy matrix that was essential to trigger the char formation. The char yield of the RGO‐PANI/Ni(OH)₂/EP composite was improved compared with that of the samples with graphene and polyaniline only. With 3.0‐wt% RGO‐PANI/Ni(OH)₂, significant reduction in peak heat release rate (40%) and peak smoke production rate (36%) was observed in the cone calorimeter tests. Thermogravimetric analysis/infrared spectrometry (TG‐IR) results indicated that the flammable volatiles of the RGO‐PANI/Ni(OH)₂/EP composite was reduced compared with those of the EP and RGO‐PANI/EP. The superior flame retardant and smoke suppressant behaviors of the RGO‐PANI/Ni(OH)₂ nanohybrid over RGO‐PANI were attributed to the combination of good barrier effect of graphene with catalytic ability of char formation of PANI and metal hydroxide.     

Conducting Polyaniline Confined in Semi‐Interpenetrating Networks

Conducting semi‐interpenetrating network composites with low conductivity percolation threshold were synthesized from waterborne conducting polyaniline (cPAn) and melamine‐urea resin. A perfect network of cPAn in the composite was observed by means of TEM (see Figure). The conductivity stability of cPAn in water was improved by confining the chain mobility of cPAn via in‐situ crosslinking of melamine‐urea resin. Cyclic voltammetry of the composites reveals electrochemical activities and reversibilities similarly to those of pure cPAn.     

Synthesis of chromene derivatives in the presence of mordenite zeolite/MIL‐101 (Cr) metal–organic framework composite as catalyst

In the present study, the synthesis of mordenite zeolite/MIL‐101(Cr) metal–organic framework (MOF) composite [MOR/MIL‐101(Cr)] using the ship in a bottle method was suggested. The properties of prepared composite and individual MOF and MOR zeolite were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption–desorption measurement, and thermogravimetric analysis (TGA). The XRD results indicated diffraction peaks for each compound (MOR and MOF) in composite. The SEM and TEM images showed the formation of plates MOR (with size of 2.5 × 3 μm) along with spherical particles MIL‐101. The Brunauer–Emmett–Teller results showed that the surface area of the composite was smaller than individual MOF and MOR zeolite. Based on TGA plots, the hybrid zeolite/MOF composite was more thermally stable compared with the isolated MIL‐101(Cr). The composite was functionalized by post‐synthetic modification to obtain acid–base bifunctionality (H‐MOR/MIL‐101‐ED) for the synthesis of chromene derivatives. The acidity from framework Al‐O(H)‐Si sites in MOR and basicity from amine groups in MIL‐101 were obtained by post‐synthetic modification.     

Preparation of polyaniline‐sulfate salt ­by emulsion and aqueous ­polymerization pathway without using ­protonic acid

Aniline was polymerized directly into polyaniline‐sulfate salt without using protonic acid in this work. Polyaniline‐sulfate salt was prepared by emulsion and aqueous polymerization pathways. The dopant i.e. sulfate ion in polyaniline‐sulfate salt was generated from ammonium persulfate which was used for oxidizing aniline. Ammonium persulfate acts both as oxidizing agent as well as protonating agent in the polymerization process of aniline to polyaniline salt. The efficiency of oxidizing and protonating power of ammonium persulfate is increased by the use of surfactant. The activity of ammonium persulfate is further increased by the use of sulfuric acid as protonic acid. It may be necessary to consider the effect of sulfate ion which is generated during the oxidation process of aniline in the chemical polymerization of aniline to polyaniline salt by ammonium persulfate either aqueous or emulsion polymerization pathway in the presence of protonic acid/functionalized protonic acid. Copyright © 2001 John Wiley & Sons, Ltd.     

Study on the Impedance Characteristic and Electrocatalytic Activity of Platinum‐Modified Polyaniline Film

The composite electrode of platinum‐modified polyaniline film is formed in 0.5 M H₂SO₄ + 3 mM H₂PtCl₆ solution by cyclic potential or constant potential deposition of platinum particles in polyaniline film. To make a comparison, the polyaniline film with the same initial thickness and structure is also treated with the cyclic potential or constant potential polarization in 0.5 M H₂SO₄ solution. The electrochemical impedance spectroscopy (EIS) of the composite electrode of platinum‐modified polyaniline film is studied in sulfuric acid solution and compared with the EIS of the polyaniline film without platinum dispersion. The results show that the different modes of potential polarization affect greatly the nature and distribution of the platinum particles, instead of the structure of the polyaniline film (matrix). The electrode reaction kinetics and mass transport process parameters involving charge transfer resistance (R_ct), double layer capacitance (C_dl), constant phase elements (CPE) and Warburg impedance in platinum substrate/platinum‐modified polyaniline film/solution interface are discussed on the basis of the interpretation of the characteristic impedance spectra and connected to the electrocatalytic activity on the oxidation of methanol molecules.     

Cure kinetics of epoxy resin-natural zeolite composites

The cure kinetics of epoxy resin and epoxy resin containing 10 mass% of natural zeolite were investigated using differential scanning calorimetry (DSC). The conformity of the cure kinetic data of epoxy and epoxy-zeolite system was checked with the auto-catalytic cure rate model. The results indicated that the hydroxyl group on the zeolite surface played a significant role in the autocatalytic reaction mechanism. This group was able to form a new transition state between anhydride hardener and epoxide group. The natural zeolite particles acted as catalyst for the epoxy system by promoting its curing rate.     

分子筛修饰电极中内电子传输机理的研究

用电化学方法聚合方法筛孔道内的苯胺,以聚苯胺分子筛修饰电极为模型研究了分子筛修饰电极的内电子传输机理,ＮａＹ分子筛的离子交换点位被苯胺修饰后,通过电聚合制得聚苯胺分子筛修饰电极（Ｐａｎ＾＋Ｙ－ＺＭＥ）,该电极通过聚苯胺链自身的电子跳跃来实现电子传输,且只有通过阴极富集后对溶液中Ｃｄ＾２＋才有响应,并能用于测定抗坏血酸。     

Radar Absorption Properties of Ni0.5Zn0.5Fe2O4/PANI/epoxy Nanocomposites

A nitrate? citrate gel was prepared from metallic nitrates and citric acid by sol? gel process and was further used to synthesize Ni_0.5Zn_0.5Fe₂O₄ nanocrystalline powder by auto‐combustion. Then, two novel 15 and 35% (w/w) magnetic Ni_0.5Zn_0.5Fe₂O₄ containing polyaniline nanocomposites, named as PANI‐Ni15 and PANI‐Ni35, respectively, were prepared via in‐situ polymerization of aniline in an aqueous solution containing proper amount of Ni_0.5Zn_0.5Fe₂O₄ magnetic powder. The incorporation of the nanopowders to PANI matrix was confirmed by X‐ray diffraction (XRD), IR and SEM. Synthesized PANI‐NiZn ferrite composite particles were subsequently added to an epoxy resin matrix to produce related nanocomposites. The morphological properties of these nanocomposite materials were investigated by SEM and TEM. The electromagnetic‐absorbing properties were studied by measuring the reflection loss in the frequency range of 8.0 to 12.0 GHz. Results showed the reflection loss of the PANI‐Ni35 composite is higher than pure polyaniline and PANI‐Ni15. The good reflection loss of the nanocomposites suggests their potential applicability as radar absorber.     

Rapid analysis of Origanum majorana L. fragrance using a nanofiber sheet,gas chromatography with mass spectrometry,and chemometrics

Headspace nanofiber sheet microextraction together with GC–MS and chemometrics resolution techniques were implemented to separate and identify the volatiles emitted by intact marjoram (Origanum majorana L.) and their relative concentrations. A novel polyaniline‐nylon‐6 nanofiber composite was applied for headspace microextraction. Characteristics such as high surface‐to‐volume ratio and π–π functional groups in polyaniline together with the NH and C=O functional groups in nylon‐6 make the polyaniline‐nylon‐6 nanofiber composite a suitable candidate for the extraction of volatiles and semivolatiles. The extracted constituents were desorbed and injected into the GC–MS system under the optimum conditions. Chemometric resolution techniques were utilized to solve the baseline offset, asymmetric peaks, and overlapped peaks problems that arise from GC–MS analysis. By means of these techniques and resolving the overlapped peak clusters, the number of identified constituents was increased to 67 compounds. The major released constituents from the intact marjoram leaves are 4‐terpineol, β‐linalool, cis‐sabinol, and trans‐geraniol.     

Composites of Polystyrene Sulfonic Acid (PSSA)‐Polyaniline and Montmorillonite Clay: Synthesis and Characterization

Polystyrene sulfonic acid (PSSA) doped water‐soluble polyaniline (PANI)/montmorillonite (MMT) clay composites were synthesized by intercalation polymerization in aqueous medium. The properties of the composites were characterized by X‐ray diffraction (XRD), transmission electron microscope (TEM), Fourier‐transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X‐ray photoelectron spectroscopy (XPS) and conductivity measurement. The results show that the composite has a mixed nanomorphology and exfoliated silicate nanolayers of MMT clay dispersed in the polyaniline matrix. This composite is more thermal stable than that without clay samples and results in good stable temperature‐dependent dc conductivity [σ_dc(T)] as temperature changed.     

Combined effect of zeolite and boric acid on thermal behavior of epoxy composites

The particles of natural zeolite in combination with boric acid were incorporated into the epoxy resin ED-20 in order to improve the thermal stability of epoxy polymer. Epoxy resin was cured using polyethylenepolyamine. Characterization of the epoxy composites was carried out by using Fourier transform infrared spectrometry, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) under flow of air and argon. The thermal behavior of the zeolite/boric acid-based epoxy composites (total percentage 15 mass%) were compared with that of 15 mass% boric acid-based epoxy system and the neat epoxy resin. TG and DSC results revealed that the combination of 5 mass% zeolite and 10 mass% boric acid significantly increased the mid-point temperature and residue, and decreased the maximum decomposition rate of the epoxy composites at the heating.     

Influence of graphene reinforcement in conductive polymer: Synthesis and characterization

Lightweight conductive polymers are considered for lightning strike mitigation in composites by synthesizing intrinsically conductive polymers (ICPs) and by the inclusion of conductive fillers in insulating matrices. Conductive films based on polyaniline (PANI) and graphene have been developed to improve through‐thickness conductivity of polymer composites. The result shows that the conductivity of PANI enhanced by blending polyvinylpyrrolidone (PVP) and PANI in 3:1 ratio. Conductive composite thin films are prepared by dispersing graphene in PANI. The conductivity of composite films was found to increase by 40× at 20 wt% of graphene inclusion compared with PVP and PANI blend. Fourier‐transform‐infrared (FTIR) spectra confirmed in situ polymerization of the polymer blend. The inclusion of graphene also exhibits an increase in Tg by 21°C. Graphene additions also showed an increase in thermal stability by approximately 148°C in the composite films. The mechanical result obtained from DMA shows that inclusion of graphene increases the tensile strength by 48% at 20 wt% of graphene reinforcement. A thin, highly conductive surface that is compatible with a composite resin system can enhance the surface conductivity of composites, improving its lightning strike mitigation capabilities.     

Allyl ether of aralkyl phenolic resin with low melt viscosity and its Alder‐ene blends with bismaleimide: synthesis,curing, and laminate properties

This paper outlines the synthesis and characterization of O‐allyl aralkyl phenolic (O‐allyl Xylok, OAX) resins having low melt viscosity and its Alder‐ene blends with 2, 2′‐bis 4‐[(4′‐maleimido phenoxy) phenyl] propane. The blends manifested a three‐stage curing pattern that converged to a two‐stage pattern on enhancing the maleimide content. The polymerization kinetics of typical allyl and maleimide rich resin systems showed apparent activation energy increasing and pre‐exponential factor decreasing from ene to the Diels–Alder step. Increased allyl content improved mechanical and impact properties of the composites at ambient temperature, although it diminished the retention of interlaminar shear strength at elevated temperature. Increased maleimide content of the resin was conducive for the higher rigidity for the composite and its retention at elevated temperature. A substantial increase in T_g (from 153°C to 280°C) and thermal stability was observed with an increase in maleimide content. High allyl content resulted in improved mechanical properties thanks to better resin–reinforcement interaction as revealed from morphological analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

Potentiometric Sensing of Heavy Metal Ions Using a Novel Zeolite Y Membrane

The application of zeolite Y membranes to the potentiometric sensing of heavy metal ions is described. Membranes are prepared from a pressed disk of zeolite Y, treated using tetraethyl orthosilicate (TEOS) as a silica source. The resulting silica‐zeolite Y composite membranes are characterized by powder X‐ray diffraction, MAS NMR and their potentiometric response to cations with a diameter greater than the zeolite Y pore. The initial response to cadmium (Cd²⁺) and lead (Pb²⁺) ions obeys the Nernst equation, including appropriate corrections for non‐ideality, although the responses decay over a time‐scale of several hours for higher concentration ratios.     

Composite polymer electrolyte membranes comprising P(VDF‐co‐CTFE)‐g‐PSSA graft copolymer and zeolite for fuel cell applications

Hybrid organic/inorganic composite polymer electrolyte membranes based on a poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) grafted membrane and varying concentrations of zeolite were investigated for application in proton exchange membrane fuel cells (PEMFC). A proton conducting comb copolymer consisting of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) backbone and poly(styrene sulfonic acid) (PSSA) side chains, i.e. P(VDF‐co‐CTFE)‐g‐PSSA (graft copolymer) with 47 wt% of PSSA was synthesized using atom transfer radical polymerization (ATRP) and solution blended with zeolite. Upon incorporation of zeolite, the symmetric stretching band of both SO group (1169 cm^?1) and the ? OH group (3426 cm^?1) shifted to lower wavenumbers. The shift in these FT‐IR spectra suggests that the zeolite particles strongly interact with the sulfonic acid groups of PSSA chains. When the weight percent of zeolite 5A is above 7%, the proton conductivity at room temperature was reduced to 0.011 S/cm. The water uptake of the composite membranes decreased from 234 to 125% with an increase of the zeolite 5A weight percent to 10 wt%. The decrease in water uptake is likely a result of the decrease in the number of available water absorption sites because of the hydrogen bonding interactions between the zeolite particles and the graft copolymer matrix. This behavior is successfully investigated by scanning electron microscopy (SEM). The results of thermal gravimetric analysis (TGA) also showed that all the membranes were stable up to 300°C. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation of polyaniline grafted multiwalled carbon nanotubes and conductive application in polyetherimide

A methodology for improving antistatic property of polyetherimide (PEI) composite using polyaniline (PANI) grafted multi‐walled carbon nanotubes (MWNTs) as conductive medium was proposed. First, the MWNTs grafted with PANI (PANI‐g‐MWNTs) were prepared by in‐situ polymerization in an emulsion system. Subsequently, PANI‐g‐MWNTs were blended with PEI using N‐methyl‐2‐pyrrolidone as solvent. After removing the solvent, the PEI/PANI‐g‐MWNT composite was prepared. As assisted conductive medium, the grafted PANI molecular chains on MWNT surface were dispersed in the PEI matrix to decrease the percolation value of the antistatic composites. The structure and morphology of PANI‐g‐MWNTs were characterized by Fourier transform infrared spectroscopy, transmission electron microscope, thermogravimetric analysis, and X‐ray powder diffraction, respectively. The dispersion of PANI‐g‐MWNTs in PEI matrix was studied by scanning electron microscope. The electrical performance was characterized by highly resistant meter. The volume resistivity of the conductivity percolation threshold was 1.781 × 10^?8 S/cm when the loading of PANI‐g‐MWNTs was 1.0 wt%. The conductivity of PANI‐g‐MWNTs/PEI composites was found to be higher than that of pristine MWNTs/PEI composite. Copyright © 2012 John Wiley & Sons, Ltd.     

Polyaniline doped by a new class of dopants,benzoic acid and substituted benzoic acid: synthesis and characterization

This work reports on a new class of dopants, benzoic acid and substituted benzoic acids such as 2‐hydroxybenzoic acid, 2‐chlorobenzoic acid, 4‐nitrobenzoic acid, 2‐methoxybenzoic acid, 3‐methylbenzoic acid, 4‐methylbenzoic acid, 3‐aminobenzoic acid and 4‐aminobenzoic acid, for polyaniline. Benzoic acids can be used to dope polyaniline by mixing benzoic acid (or a substituted benzoic acid) with polyaniline in the common solvent 1‐methyl‐2‐pyrrolidone. Properties of benzoic acid doped polyaniline salts are studied using Fourier transform infra‐red, X‐ray diffraction spectroscopy, scanning electron microscopy, thermogravimetric analysis and conductivity measurements. The conductivity of polyaniline‐benzoic acid salt was found to be high (10⁻² S/cm) when compared to polyaniline‐substituted benzoic acid salts (10⁻³–10⁻⁵ S/cm). Copyright © 2005 John Wiley & Sons, Ltd.     

Preparation and characterization of natural zeolite supported nano TiO2 photocatalysts by a modified electrostatic self‐assembly method

Natural zeolite supported nano TiO₂ photocatalysts were prepared by a modified electrostatic self‐assembly (ESA) method. First, γ‐mercaptopropyltrimethoxysilane with sulfhydryl (―SH) functional groups was modified on the zeolite powders by using a ‘dry process’. Second, silane with ―SH functional groups was oxidized to sulfonate (―SO₃H) groups by using a hydrogen peroxide/glacial acetic acid mixed solution, and the surface of ―SO₃H silane–zeolite was electronegative charged due to the ionization of ―SO₃H. Third, the hydrolytic titanium polycation from TiCl₄ solution assembled onto the electronegative charged zeolite under electrostatic attraction in the reaction solutions. Finally, zeolite supported nano TiO₂ photocatalysts can be obtained after the above compounds calcined at certain temperature. The samples were characterized by X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface areas, Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS) and X‐ray fluorescence (XRF). The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in aqueous solution. The results showed that ESA method effectively improved the composite efficiency of zeolite with TiO₂. The photocatalysts prepared by ESA method exhibited higher photocatalytic and recycling activities than that of traditional method. Copyright © 2014 John Wiley & Sons, Ltd.     

Conducting polyaniline/nano-zinc phosphate composite as a pigment for corrosion protection of low-carbon steel

Zinc phosphate (Zn₃(PO₄)₂) nanocrystals were synthesized and used for making conducting polyaniline/nano-zinc phosphate composite by chemical oxidative method. The product was characterized by UV–visible absorption spectroscopy. The crystal structure, morphology and thermal stability of the product were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and thermo gravimetric analysis, respectively. The epoxy-based paint containing conducting polyaniline/nano-zinc phosphate composite pigment was applied on low-carbon steel samples. Corrosion protection performance of the painted low-carbon steel samples in 3.5 mass % sodium chloride solution was evaluated using electrochemical technique. Transmission electron microscopic image revealed the formation of core shell structure of the composite. Composite was found to be more thermally stable than the conducting polyaniline. The corrosion rate of conducting polyaniline/nano-zinc phosphate-painted low-carbon steel was found to be 5.1 × 10^?4 mm per year, about 34 times lower than that of unpainted low-carbon steel and 10 times lower than that of epoxy nano-zinc phosphate paint-coated steel. The study reveals the possibility of using conducting polyaniline/nano-zinc phosphate as a pigment for corrosion protection.