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In this paper we report the fabrication of Schottky barriers using polyaniline (PANI) doped with trifluoroacetic acid (TFA). The PANI doped with TFA (PANI-TFA) was prepared by chemical oxidative polymerization using an indirect synthetic route known as doping-dedoping-redoping. The structural, morphological, optical and thermal properties of the obtained doped polyaniline (PANI-TFA) were studied by FTIR, SEM, UV−Vis-NIR, and TGA and DSC, respectively. Its electrical conductivity was measured at room temperature with a four-probe method. FTIR and UV−Vis-NIR analysis confirmed the structure and the doping of the emeraldine base by the trifluoroacetic acid. Four-probe measurements showed that the electrical conductivity of the PANI-TFA sample was around 0.226 S/cm. In addition, a Schottky diode with configuration Al/PANI-TFA/Ag was fabricated. Current–voltage (I−V) and capacitance–voltage–frequency (C−V−f) measurements were used to characterize the fabricated Al/PANI-TFA/Ag device. It was found that the (I−V) plot was nonlinear and asymmetric and the (1/C2−V) plots were almost linear in reverse bias voltage indicating that the Al/PANI-TFA/Ag device exhibited behavior similar to a diode with rectification behavior and followed the modified Schottky diode equation. The diode parameters, including the ideality factor, barrier height, saturation current and carrier concentration, were calculated using the modified Shockley equation.

During the extrusion of thermoplastic particulates, the major problem is to adjust and optimize the experimental conditions of temperature and rotational speed of the screw, to decrease porosity defects, resulting from the coalescence of the polymer grains. In this work, a study of high-density polyethylene (HDPE) coalescence as a function of temperature and shear rate is conducted, with modeling of this phenomenon by the Bellehumeur model. The effect of applying a shearing force to get closer to the conditions of extrusion is also evaluated using the equations of Yao-Yuan Chang and Shi-Yow Lin, which represent the latest version of the changes to the Laplace equation. Results show that the coalescence changes as a function of time despite the slight increase in the shear rate between 1 to 7 s−1, it tends clearly to reduce the rate of coalescence up to 60% and thus promotes deformation and rupture. In addition, the studied Bellehumeur modeling of coalescence reveals only a mild deviation respected to experimental data even the complicated measurement conditions.

This work is devoted to the study of the cationic ring opening polymerization of tetraphenyltetramethylcyclotetrasiloxane (D4Ph,Me), using a solid green catalyst prepared by the activation of a natural clay by sulfuric acid (Maghnite-H+). This treatment leads to the spacing of the montmorillonite sheets due to the substitution of the existing interlayer cations by the protons of the acid. This consequence is clearly shown on the X-ray diffraction (XRD) spectrum. The polymerization reaction proceeded in bulk and under mild conditions. Various tests were carried out by changing the temperature, the time and the catalyst mass content in order to increase, at the same time, the yield of the reaction and the average molecular mass of the polyphenylmethylsiloxane (PPMS) obtained. The structure of the PPMS obtained was identified by infrared (IR), 1H nuclear magnetic resonance (NMR) and 13C NMR analyses over different periods of time. The thermal behavior was investigated by differential scanning calorimetry (DSC) analysis. At the end, in order to show the role played by the Maghnite-H+ during the various reaction stages, a reaction mechanism was proposed.

A new procedure for synthesizing a dimethyl siloxane polymer is addressed in the present work, which is based on the use of Maghnite-H+ as a green and environmentally friendly catalyst in the polymerization of dodecamethylcyclohexasiloxane (D6). The Maghnite-H+ is natural smectite clay, activated by a strong acid, sulfuric acid is generally the most used. The impact of acid activation appears in increasing the basal spacing of the Maghnite, it is confirmed by XRD analysis. The solvent-free polymerization of D6 by cationic route using the Maghnite-H+ has been made, the product obtained was characterized by different methods of analysis as IR, 1H NMR, 13C NMR and GPC. Temperature, time and mass content of catalyst were optimized so to obtain a yield and an average molecular mass large enough and without cyclic structures. Also, the thermal behavior of the polymer was investigated by DSC. At the end, a reaction mechanism was proposed which describes in detail the role played by the Maghnite-H+ during the various stages of the reaction.

Magnetized (PANI-coated Fe3O4) epoxy resin was synthesized to produce $X$ -band microwave absorbing structures (MASs) with tuning thickness and fillers ratio. The structure and crystallinity of materials were checked by SEM and X-ray diffraction. It was found that the thickness, amount, and ratio of magnetized PANI-coated Fe3O4 affect the microwave absorption properties. Single layer MAS with 3 mm showed a reflection loss (RL) of −54 dB at 8.73 GHz and −41 dB at 9.52 GHz. However, a double-layer absorber based on 0.9 mm of the matching layer of PANI and the absorbing layer of magnetized (PANI-coated Fe3O4) epoxy resin composite with a thickness of 1.8 mm show a minimum RL value of −38 dB at 9.82 GHz and an absorption bandwidth of about 3.55 GHz with RL below −10 dB. In addition, by rising thicknesses the RL peak shift to lower frequency. A materials prepared with thin double-layer structure have a high absorption performances and broader bandwidth in $X$ -band.

The present work is devoted to the synthesis and characterization of vinylsiloxane polymers produced by the use of an activated natural catalyst known as Maghnite-H+. The cationic ring opening polymerization of pentavinylpentamethylcyclopentasiloxane (V5D5) made it possible to obtain the desired polymeric materials. Through this study, we have adapted a new strategy of synthesis of a siloxane polymer with relatively high molecular mass, using a solid initiator activated by sulfuric acid, which has enabled us to combine the ecological aspect of synthesis and the effectiveness of the catalyst in this kind of reaction. Structural [infrared (IR), proton and carbon nuclear magnetic resonance (1H NMR and 13C NMR)], thermal differential scanning (DSC) and chromatographic (GPC) characterization methods have allowed the products obtained to be identified and their various properties to be focused on. The kinetic study was made to determine the order of the reaction. The proposed reaction mechanism shows the advantages of Maghnite-H+.

The polymerization of octamethylcyclotetrasiloxane (D4) catalyzed by Maghnite-H+, a nontoxic and green solid catalyst, is studied. The Maghnite-H+ is a montmorillonite type 2:1 dioctahedral phyllosilicates whose interlayer ions are exchanged by hydronium ions after activation with sulfuric acid which gives it its catalytic appearance. D4 was polymerized cationically by ring opening at 60 °C without solvent using Maghnite-H+ contents less than 5% by weight. The molecular structure of the polymer obtained was identified by IR, 1H NMR and 13C NMR. The DSC was used to study the thermal properties. The operating conditions were optimized so that we can achieve best performance for obtaining a linear polymer with high average molecular mass. The variation of the molecular mass distribution was verified by GPC. Finally, a reaction mechanism was proposed to show the role of the Maghnite-H+ during the different steps of the reaction.

A new green technique to synthesize polysiloxane-type polymers is suggested based on use of chemically modified clay (Maghnite-H+) as heterogeneous, cost-effective, environmentally friendly catalyst for polymerization of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (V4D4) under gentle conditions and without solvent. Maghnite-H+ is an ion-exchanged montmorillonite prepared by treatment with sulfuric acid, which leads to increased interplanar spacing due to intercalation of acid protons between sheets, a crystalline change clearly seen in the X-ray diffraction (XRD) spectrum. Polymers obtained under different conditions were characterized by infrared (IR) and 1H and 13C nuclear magnetic resonance (NMR) analyses and their thermal behavior studied by differential scanning calorimetry (DSC) analysis. The average molecular mass and dispersity were followed by gel permeation chromatography (GPC) by varying the operating conditions. A reaction mechanism is proposed to understand the role played by Maghnite-H+ during the various stages of the reaction.

International audience; The objective of this work is to initiate the discussion about multiphysics relationships between the molten and solid states of high-density polyethylene (HDPE). The extrusion and the injection processes are employed to prepare samples, and the experimental procedures, using differential scanning calorimetry, dynamic thermomechanical analysis (DMTA), thermal gravimetric analysis, and rheological measurements, are defined to choose the optimal variables. After different characterizations, the extrusion and injection temperatures of 220 and 230 °C have been chosen. To investigate the viscoelastic behavior of HDPE, the DMTA is used. To perform the high strain rate tensile tests, tensile machine was equipped with a specific furnace. Two temperatures, −20 and 20 °C, with strain rates varying from 0.001 to 100 seconds−1 were used to compare the flow characteristics. Results showed that by increasing the strain rate the molecular mobility of the HDPE chains is decreased. In addition, to the tests at −20 °C, the increase of Young's modulus can be properly observed, under high strain rates.

The original publication of this article unfortunately contains error. The word “extrusion” was spelled incorrectly as “extrussion” in the article title.

In this study, we propose Maghnite- $$\hbox {H}^{+}$$ , as an ecological, cost-effective and easily renewable catalyst, for the polymerization of decamethylcyclopentasiloxane (D5). The Maghnite is a clay consisting primarily of smectite minerals (montmorillonite group), which can be activated/reactivated through a simple process, by replacing interlayer cations by protons. Linear polymers with higher molecular mass and narrower molecular mass distribution (MMD) can be obtained with less cyclic by-products, using Maghnite- $$\hbox {H}^{+}$$ . The reaction was investigated in bulk, taking into account the effect of time, temperature and amount of catalyst on the monomer conversion and MMD. When the yield rises to 96%, the MMD is broadened, suggesting the formation of cyclic oligomers and/or crosslinking bonds, this was confirmed experimentally by infra-red spectroscopy, proton nuclear magnetic resonance ( $$^{1}\hbox {H}$$ NMR) and $$^{13}\hbox {C}$$ NMR analyses. The kinetics have been also studied; the reaction is first order in the monomer. The proposed reaction mechanism shows clearly the role of Maghnite- $$\hbox {H}^{+}$$ for D5 polymerization.

Conducting polymer blends were prepared using polyaniline doped with para- toluene sulfonic acid (PTSA-PANI) and a polyester polyol-based polyurethane (PU). The morphological, thermal and dielectric properties of the PTSA-PANI/PU blends in the frequency range of 1–5 GHz (S band) were investigated. It was found that the morphology of the samples was affected by the PTSA-PANI loading, resulting in the formation of agglomerates and pathways when above 10 wt%. The thermal stability of the composites was improved with increased PTSA-PANI loading. The electrical conductivity percolation threshold was obtained at 2.5% of PTSA-PANI loading and the electrical conductivity reached the value of 0.13 S/m at a PTSA-PANI loading of 30 wt%. The obtained results for the PTSA-PANI/PU blends prepared indicate a high potential for their successful use in electrical and electromagnetic applications.

The purpose of this study was to obtain poly(furfuryl alcohol) nanocomposites with Algerian organically modified clay (termed 12-montmorillonite). The formation of poly(furfuryl alcohol) was confirmed by infrared spectroscopy (IR); the prepared nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The evolution of mechanical properties was also studied. The obtained results confirm the intercalation of molecules of salt in the clay layers, and a good interaction with the polymer, showing the formation of intercalated and/or exfoliated structures. The nanocomposites showed higher thermal stability compared to pure polymer, and the mechanical properties presented interesting and promising results.

In this study, we propose a novel conducting and soluble polyaniline salt prepared by chemical polymerization in the presence of new doping agent (IAs). This last is prepared by sulphonation of itaconic acid (IA) with concentrated sulphuric acid in THF. The obtained doped polyaniline (PANI-IAs) is extremely soluble in dimethyl sulfoxyde (DMSO) at room temperature, in which the solubility reach 44 mg mL-1. The conductivity measurement of doped polyaniline powder precipitated in THF as dispersing medium gave a value of 0.13 S cm-1 when the emeraldine base form of polyaniline is fully protonated. The polyaniline salt sample is characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction, UV-Visible spectra and FTIR spectra.

The aim of this work is to obtain an organophilic montmorillonite with Algerian modified clay (termed 12-maghnite). The organic surfactant used in this preparation is 12-aminolauric acid. The functionalization of the organophilic clay was confirmed by infrared spectroscopy (IR). The obtained organoclay was characterized by X-ray diffraction (XRD) which shows a remarkable increase of the basal distance that reaches up to 17.62 A. The transmission electron microscopy analysis (TEM) supports fully the result obtained by XRD analysis. The novelty of this work is the exploitation of local clay that is widely available, inexpensive and has excellent properties and high quality features, which make it the subject of continuing research. These results will be a starting point and an essential reference for a comparative study, with the results of future works concerning the synthesis of Polymer/12-Maghnite nanocomposites.

Furfuryl alcohol (FA) which is derived from lignocellulosic biomass polymerizes into poly(furfuryl alcohol) (PFA) under acidic catalysis. A greener and more sustainable catalytic pathway was suggested in order to replace hazardous acidic catalysts by Algerian modified clay (maghnite-H+ or mag-H+). The possibility of the polymerization of FA by mag-H+ was reported, and it was found that the polymerization of FA was initiated by mag-H+ in dichloromethane. The reaction parameters such as time, temperature, and mag-H+/monomer weight ratio were optimized to improve the yield of the reaction and increase the average molecular weight. The kinetics indicated that the polymerization rate is first-order with respect to monomer concentration. The structural analysis of the polymer was carried out by IR, 1H NMR and 13C NMR spectroscopies. Thermal properties of the polymer were studied by TGA and DSC analyses. The novelty of this work is the exploitation of local clay that is widely available, inexpensive and has excellent properties and high quality features, which make it the subject of continuing research. These results will be a starting point and an essential reference for a comparative study, with the results of future work concerning the synthesis of PFA/maghnite nanocomposites.

Nylon 6/clay nanocomposites (1, 3, 5, and 10 % (w/w) 12-maghnite based on the e-caprolactam content) were synthesized by in situ polymerization. 12-maghnite is a montmorillonite silicate sheet clay was prepared through a straightforward exchange process, using a green natural clay from Maghnia (west of Algeria). Fourier transform infrared spectroscopy confirmed the formation of nylon 6. X-ray diffraction and transmission electron microscopy revealed that the modified montmorillonite layers were uniformly dispersed and exfoliated in the nylon 6 matrix for low levels of clay, while intercalated structures and immiscible regions were detected for high levels. Thermogravimetric analysis revealed that the thermal properties of nylon 6/clay nanocomposites were enhanced with increasing 12-maghnite levels ((500 C). Additionally, the nanocomposites showed a remarkable improvement in their mechanical properties compared to pure polymer.

The ring opening bulk polymerization of ε-caprolactam catalyzed by Maghnite-H+ was reported. Maghnite-H+ is a montmorillonite silicate sheet clay was prepared through a straight forward proton exchange process. The effect of the amount of catalyst, and temperature was studied. Increasing Maghnite-H+ proportion and temperature produced the increase in ε-caprolactam conversion. The kinetics indicated that the polymerization rate is first order with respect to monomer concentration. Mechanism studies showed that monomer inserted into the growing chains with the acyl–oxygen bond scission rather than the break of alkyl–oxygen bond. © 2014 BCREC UNDIP. All rights reservedSubmitted: 3rd October 2013; Revised: 28th February 2014; Accepted: 1st March 2014[How to Cite: Kherroub, D.E., Belbachir, M., Lamouri, S. (2014). Cationic Ring Opening Polymeriza-tion of ε-caprolactam by a Montmorillonite Clay Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 9 (1): 74-79. (doi:10.9767/bcrec.9.1.5555.74-80)][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.1.5555.74-80]

The purpose of this study was to obtain polyamide-6 nanocomposites with national organically modified clay (termed 12-montmorillonite). The formation of polyamide-6 was confirmed by infrared spectroscopy (IR), the prepared nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The evolution of mechanical properties was also studied. The obtained results confirm the intercalation of molecules of salt in the clay layers, and a good interaction with the polymer, showing the formation of intercalated and/or partially exfoliated structures. The nanocomposites showed higher thermal stability compared to pure polymer, and the mechanical properties presented interesting and promising results.

In this work, conducting poly(aniline)/zeolite (PANI-HY) composites used for a carbon dioxide (CO2) gas sensor, were prepared in two ways, The first method utilized in situ polymerization of aniline with ammonium perdisulfate as an oxidizer in an aqueous medium with addition of zeolite type HY-free acids. The second method involved the dispersion of various fractions of HY (5, 10, 15, 20 and 50 wt %) in a PANI-HCl matrix by physical mixing. We focused mainly on studying the conductivity with respect to temperature and gas environment. The synthesized conducting composites were characterized by FTIR, SEM, ultraviolet-visible spectroscopy, porosity and X-ray Diffraction. The PANI-HY composites showed the ability to detect CO2 at room temperature. An original dispositive is used to study the effect of temperature on the conductivity of new materials based mainly on the conducting composites containing poly(aniline) and zeolite, these later exhibit reaction toward the carbon dioxide gas.

International audience; In this work, two types of hybrid composite materials were elaborated. The first based on polyaniline (PANI) doped Camphor Sulfonic acid (CSA), Carbon-Coated Cobalt (CCo), and FeNi nanoparticles dispersed in polyurethane. A value of 104 S/m of conductivity and a 90 dB of shielding effectiveness in multilayer structure were obtained over the 8–18 GHz frequency band. The second type, based on PANI doped para-toluene sulfonic acid (PTSA), dispersed in epoxy resin with FeNi nanoparticles. A thick material with moderate conductivity and high attenuation of electromagnetic waves was obtained. It was found that a PANI-PTSA/FeNi/epoxy resin composite with thicknesses of 9.7 and 6.5 mm had, respectively, reflection loss values of −22 dB at 9.52 GHz, and −20.7 dB at 14.7 GHz. The electromagnetic properties of the elaborated structure hybrid materials can be optimized to increase the electromagnetic reflection–absorption properties. Thus, the obtained structure can be used in shielding and radar absorbing materials applications.

Hybrid organic/inorganic electromagnetic absorbing materials (EMAMs) based on polyaniline (PANI) and magnetite (Fe 3 O 4 ) fillers dispersed in epoxy resin matrix were successfully prepared for electromagnetic applications. The effects of PANI and Fe 3 O 4 loading on permittivity, permeability and microwave absorption properties were studied. The structure and the morphology of the elaborated composites were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electromagnetic properties and absorbing behaviors were performed over frequency range of 12.4–18 GHz (Ku-band). The results show that synthesis parameters such as amount and particle size of PANI and used Fe 3 O 4 affect significantly the morphology, the conductivity, and the microwave absorption properties of the final materials. It was revealed that the electromagnetic parameters were higher in hybrid PANI/magnetite/epoxy resin than in dielectric PANI/epoxy resin composites. The permittivity and the permeability parameters increased to high values with the rate of fillers in the composite and remained constant with the frequency. A minimum reflection coefficient (RC) of −42 dB was observed at 16.3 GHz with a thickness around 1 mm for composites containing 15% of PANI and 10% of Fe 3 O 4 ( ɛ ′ = 10) and −37.4 dB at 14.85 GHz for the composite of 15% of PANI and 25% of Fe 3 O 4 ( ɛ ′ = 17) . However, a composite made with only 20% of PANI ( ɛ ′ = 8.5) showed a minimum reflection coefficient of −11 dB at 18 GHz with the same thickness. The possibility to modulate the electromagnetic properties of the composite materials is of a great interest to fabricate microwave absorbing and electromagnetic shielding materials with high performances.

Composites based on conductive organic/inorganic fillers dispersed in insulating matrix have been widely investigated because of their widespread applications such as electromagnetic shielding, electrostatic discharge, and sensors. In this context, novel composite materials based on epoxy resin matrix charged with polyaniline (PANI)-doped para-toluene sulfonic acid were elaborated. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to check the structure and the morphology of the samples. Viscoelastic behavior and thermal stability of the composites were explored by dynamic mechanical thermal analysis and thermogravimetric analysis. It was shown that the PANI particles exhibited a partial crystalline structure and were homogeneously dispersed in epoxy matrix. Consequently, this structure affected the thermal stability and viscoelastic properties of the composites. Furthermore, the dielectric and electrical properties were investigated up to 1 MHz. Measurements of dielectric properties revealed that with loading fillers in matrix, the dielectric parameters increased to high values at low frequency then decreased at values around 40 and 32 of real and imaginary parts, respectively, at 1 MHz with 15% of PANI content. Copyright © 2011 John Wiley & Sons, Ltd.

This work focuses on the elaboration and characterization of conducting polymer composites based on polyaniline (PANI) dispersed in an epoxy resin (ER) matrix and cured using an anhydride without a catalyst. PANI-doped benzene sulfonic acid was successfully synthesized in this manner and used as conducting filler. The effect of heating rate and PANI loading level on the curing process was investigated by differential scanning calorimetry in the dynamic mode. Furthermore, the phase structure, viscoelastic behavior and hardness of the composites were explored by dynamic mechanical thermal analysis and Vickers tests. The structure and morphology of the samples were investigated by scanning electron microscopy, which revealed behavior that varied as a function of the concentration of PANI in the composites. Dielectric properties were investigated up to 1 MHz. The electromagnetic shielding effectiveness of the composites was measured in the microwave band from 8 to 18 GHz. It was found that the electrical properties of PANI were influenced by elevated curing temperature of the ER, a variable that significantly affected the composite characteristics. In addition, the dielectric properties, curing parameters, viscoelasticites and electromagnetic behaviors of the composites were affecting by increasing the concentration of PANI filler in the matrix. Polyaniline (PANI)-doped benzene sulfonic acid (BSA) with moderate conductivity and high-dielectric properties affects the characteristics of its composites when its loading was below 15%. In addition, heating rate and curing temperature influenced the electrical properties of PANI, which affect composite properties as it was cured without catalyst. Moreover, dielectric, electromagnetic, thermomechanical behaviors and curing parameters were also affected by increasing PANI in matrix.

Conducting polymer composites, which are simply physical mixtures of an insulating polymer matrix and intrinsically conducting polymers, are promising new materials for various applications such as antistatic coatings, shielding and electromagnetic absorbers. In this context, a novel conducting composite was successfully produced. It is based on epoxy resin and polyaniline (PANI) doped in benzene sulfonic acid, which was used as conducting filler. The effect of PANI loading levels on the structural, morphological, thermal, electrical and dielectric properties was explored using techniques, such as Raman, Fourier transform infrared and ultraviolet-visible-NIR spectroscopy, X-ray diffraction, atomic force microscopy, scanning electron microscopy, thermogravimetric analysis and differential scanning calorimetry. The electrical behavior and morphology of the synthesized PANI revealed disorder and defects. In addition, as the applied voltage is increased, the current through the sample increases rapidly. The conductivity and dielectric properties were also investigated at room temperature in the frequency range of 1 MHz–1 GHz. The dielectric constant was shown to increase with increased loading at low frequencies and then decreases rapidly, reaching a constant value at higher frequencies. In addition, the AC conductivity of the prepared composites increases with the addition of PANI and is higher at high frequencies. Furthermore, the stability of the composites was found to be influenced by increasing the amount of PANI filler in the matrix. The defects and heterogeneous system of polyaniline (PANI) doped in benzene sulfonic acid (BSA) with a crystalline region dispersed in an amorphous low-conducting region as shown in the scanning electron microscopy micrograph reveal the current–voltage characteristic, which shows a nonohmic variation. It increases in current with applied voltage owing to the conduction mechanisms of PANI due to the formation of polarons and bipolarons. As the applied voltage increases, the formation of polarons and bipolarons increases rapidly, contributing to higher values of current through sample. This characteristic affects the dielectric behaviors of the elaborate composites.

This paper deals with the preparation of polyaniline (PANi) covalently grafted onto aniline-terminated porous silicon (PSi) substrate. Aniline-terminated PSi surface was obtained in a two-steps procedure. First, oxidized PSi surface was reacted with 3-bromopropyltrichlorosilane to yield a brominated surface. Aniline-terminated PSi surface was realized by reacting brominated PSi layer with aniline molecules at 60 °C for 24 h. The aniline moieties anchored onto the PSi surface were used as reactive sites for graft polymerization of aniline monomer. The composition and morphology of the resulting surfaces were examined by Fourier transform infrared spectroscopy (FT-IR), secondary ion mass spectrometry (SIMS) and scanning electron microscopy (SEM). Furthermore, the optical properties of all functionalized materials involved in the synthesis protocol were characterized using photoluminescence (PL).

In this study, the dibenzoyl-L-tartaric acid (DBTA) was used as doping agent to synthesis polyaniline (PANI) by direct oxidative polymerization of a chiral aniline monomer repeat unit. The influence of DBTA on the electrical performances of the polyaniline was studied with the synthesis conditions, particularly the molar ratio of DBTA to aniline and the presence of methanol. The spectral characterization (FT-IR and UV-visible-NIR), the thermal (TGA), electrical properties at macroscopic scale (I-V, C-V curves and the gap) and the morphology of the PANI have been investigated. From the results it's found that synthetic conditions have a great influence on the electrical properties of PANI-DBTA. In addition polyaniline micro-fibres can be obtained when using methanol as a solvent of DBTA.

In this study, a new and easy strategy was discussed for the purpose of synthesizing of a polymer of phenylmethylcyclosiloxane type (PPMS). The cationic ring opening polymerization of triphenyltrimethylcyclotrisiloxane (D3Ph,Me) was initiated by a solid, efficient and environmentally-friendly catalyst called Maghnite-H+. Maghnite-H+ is a natural clay composed essentially of montmorillonite, it is activated with an acid treatment by replacing the interlayer ions by protons, that results to the increase of the basal space, this may be confirmed by XRD analysis. The reaction was carried out without solvent at different temperatures and for different periods of time, using also several catalyst contents. Subsequently, the operating conditions were opted in order to obtain a maximum yield of the linear polymer and a high average molecular mass as well. The structure of polymers obtained was confirmed by IR analysis. 1H NMR and 13C NMR analyzes were used to follow the crosslinking of polymer chains over time. The thermal behavior was investigated by DSC analysis. The average molecular mass and the polydispersity indices were determined by GPC.

Polymer blends based on nanostructured polyaniline (PANI) doped with hydrochloric acid (HCl) and para-toluene sulfonic acid (PTSA) introduced into aliphatic polyurethane matrix (PU) are synthesized to produce flexible thin composite films for microwave absorbers. The effects of dopant type, PANI content and film thickness on morphologies, dielectric and microwave absorption properties in the X-band are studied. It reveals that real and imaginary parts of the complex permittivity are proportional to filler concentrations and type of doped PANI. The PANI-PTSA/PU films show higher permittivity and better microwave absorbing properties than PANI-HCl/PU for the same weight fraction of PANI. The minimum reflection loss RL(dB) values for the PANI-PTSA/PU are −37 dB at (20% PANI and 11.6 GHz) and −30 dB at (15% PANI and 11.3 GHz) for thicknesses of 1.2 and 1.6 mm, respectively. These high values of reflection losses make the obtained lightweight and flexible composites promising radar absorbing materials (RAM). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40961.

Polyaniline free-standing films behavior has been investigated by electrical measurements, spectral, thermal and morphological analyzes. Two categories of thin films were elaborated. The first one represents films containing intrinsic conducting polymer, Polyaniline (PANI), doped by dipping method in sulfanilic acid solutions for various period of time. The second category contains conducting polymer composite; Polyaniline-Polyvinylchloride (PANI/ PVC), prepared by co-dissolution method using sulfanilic acid as a doping agent and N-methylpyrrolidone (NMP) as solvent and deposited on glass substrate using the spin coating technique. The effect of doping time, PANI fraction and film thickness on the conductivity has been studied principally by electrical measurements.

Often in dry friction, material transfer occurs as a discontinuous film consisting of discrete particles, strongly adhering to the substrate. On smooth surfaces this leads to the formation of asperities interacting both mechanically and physico-chemically with the counterface. A simple analysis of the forces acting on a single asperity allows the definition of the conditions of stability and hence of transfer particle existence. The model developed is illustrated by transfer particle density variations (assessed by image analysis) as a function of experimental conditions for various materials whose surface energies have been determined by inverse gas chromatography or wetting contact angles. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Lahaina, Hawaii, October 16–20, 1994

The friction of pure polyethylene and acrylate grafted films or mixtures of polyethylene and a poly (ethylene-butylacrylate-maleic anhydride) terpolymer is examined at low speed for sliding on a poly(methylmethacrylate)(PMMA) or polyvinylchloride (PVC) substrate. In all cases, the friction coefficient μ at equilibrium is proportional to the adhesion energy of the same films as determined by a peel test. This study shows how much for smooth surfaces, interfacial and mechanical properties intervene simultaneously in polymer-polymer friction.

Soluble emeraldine-base (PANI-EB) was prepared and its structure was characterized using 1H, 13C and 2D (COSY, HMQC and HMBC) NMR. The solubility of the polymer in two solvents (N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO), the structure of the solution (aggregation) and the behavior of polyaniline were studied by viscometry and by dynamic light scattering (DLS) in dilute solution. Viscometric behavior in NMP and Huggins constant determination confirm supramolecular interactions also evidenced by DLS; at end, the molecular weight of the soluble fraction of PANI-EB is determined.

For its potential performances to be expanded, cellulose needs to be processed in different ways. Therefore, an object of the present work was to provide a chemical modification of cellulose through: a specific finish with two quaternary ammonium salts (namely Aliquat 336 and Aliquat 1529, respectively). Chemical grafting of beta-cyclodextrin derivative (beta-CD) onto fibers followed by the inclusion of benzoic acid in the grafted CD cavities as a probe chemical. Physicochemical properties and performances of the untreated and treated fibers have been determined with infrared spectra, microscopy, swelling measurements, antimicrobial finishing tests, and dye adsorption. Our results show that cellulose fibers can be efficiently modified with no significant changes in its structural and surface properties; the treated fibers show an attractive behavior in swelling, dye adsorption and antibacterial activity.

This work is part of a systematic investigation concerning the mechanisms of transfer film formation in dry friction and their influence on frictional forces. This paper deals mainly with discontinuous films and is characterised by an experimental approach using image analysis to quantify the discrete particles formed on smooth surfaces, combined with the analysis of the parameters controlling transfer particle stability. This work aims to complete the previous investigations in the case of polymers, and check to what extent adhesion (measured by peel test) affects transfer particle density. It is based on the use of four well characterised films of polyethylene, differing mainly by the amount of grafted acrylic acid (respectively 0.0, 0.5, 1.0, and 2.0%). The variations of particle density with normal load, displaying either positive or negative slopes are of great interest. In agreement with previous hypotheses, these variations may be interpreted in terms of shear stresses τ, provided that they include the well known pressure dependence of τ.