Synthesis and conductive properties of polypyrrole nanocomposites

This paper studies the impact on the different surfactants and capacity of the oxidant for the synthesis of polypyrrole (PPy). The soluble PPy has also been studied. PPy was characterized mainly from the surface morphology, Fourier transform infrared spectroscopy, and conductivity sigma. First, using cetyltrimethylammonium bromide (CTAB) as the surfactant doped in an acid doping environment and without using ammonium persulfate (APS) as an oxidant, we determined the different capacities of the oxidant to synthesize the PPy. Scanning electron microscopy, Fourier transform infrared spectroscopy, and a four-probe conductivity meter were used to characterize the PPy. The acid doping conductivity was found to be 25 S/cm higher. Then, the solubility of polypyrrole was studied by doping with sodium dodecyl benzene sulfonate (SDBS), polyethylene glycol (PEG), and poly(styrene sulfonate) (PSS), proceeding the above-mentioned characterization.     

Thermal properties of PMMA/montmorillonite clay nanocomposites

Polymer/Clay offer tremendous improvement in wide range of physical and engineering properties for polymers with low filler loading. In nanotechnology polymer/clay nanocomposites use smectitetype clays that have layered structures. In this work, Poly (methyl methacrylate) (PMMA) was synthesized by free radical addition polymerization in the presence of high power ultrasound. The Poly (methyl methacrylate) (PMMA)-Montmorillonite (MMT) clay nanocomposites were synthesized by two different techniques viz., ultrasonic mixing and magnetic stirring. An analysis of the XRD data confirms that the composites are in the nanometer scale. The FTIR spectra show that there is strong interaction between the clay and the polymer that enhances the thermal stability. The thermal stability of the experimental nanocomposite prepared by the two processes is compared. Further analysis of XRD data shows that intercalation as well as exfoliation has taken place in both the types of nanocomposites preparation. An analysis of the TG, DTG curves reveal that the thermal stability is found to increase by nearly 30% for ultrasonic mixing than that of magnetic stirring.     

Biodegradable nanocomposites from toughened polyhydroxybutyrate and titanate-modified montmorillonite clay

Montmorillonite clay treated with neopentyl (diallyl)oxy tri(dioctyl) pyrophosphato titanate was used as a reinforcement for toughened bacterial bioplastic, Polyhydroxybutyrate (PHB) in order to develop novel biodegradable nanocomposites. The modified clay, PHB, toughening partner and specific compatibilizer were processed by extrusion followed by injection molding. Different microscopy and goniometry techniques, rheology analysis, X-ray diffraction and thermo-mechanical testing were used to characterize the nanocomposites. Results showed that the nanocomposites with 5 wt% titanate-modified clay loading exhibited about 400% improvement in impact properties and 40% reduction in modulus in comparison with virgin PHB. The novel aspect of the titanate-based modification was that the nanocomposites still maintained nearly the same impact strength value as that of toughened PHB. The diffraction patterns suggest exfoliation of the organically modified clays and this was further supported by transmission electron microscopy and melt rheological analysis. The mechanical properties of the nanocomposites were correlated with a modified Halpin-Tsai theoretical model and the predictions matched significantly with the experimental results. Toughened and compatibilized PHB showed significantly lower biodegradation rate than virgin PHB and most significantly the addition of the titanate-modified clay in the same formulation enhanced the biodegradation several fold.     

Electromagnetic absorption efficiency of polypropylene/montmorillonite/polypyrrole nanocomposites

Electrical conductivity and dielectric properties have been studied for two types of polypropylene composites containing conducting phase. One type comprised conducting polymer–polypyrrole while the second employed montmorillonite particles coated with conducting polymer–polypyrrole. Composites’ shielding properties were estimated based on their previously determined electromagnetic characteristics. Unlike a basic binary polypropylene/polypyrrole composite, the ternary sample with multicomponent montmorillonite particles exhibits higher dielectric losses and consequently a significant rise in shielding efficiency in the radio-frequency range of 0.1–1.5 GHz. This stems from the presence of highly polarizable multicomponent montmorillonite anisotropic lamellar particles with polypyrrole conducting layer, which considerably increases the complex permittivity of the composite.     

Double corrosion protection mechanism of molybdate-doped polypyrrole/montmorillonite nanocomposites

Nanocomposites based on polypyrrole (PPy) doped with molybdate (PPy(MoO₄)) and montmorillonite (MMT) were prepared by chemical polymerisation. The morphology of nanocomposite particles was studied by scanning electron microscopy. The chemical structure of conducting polymers (CPs) in nanocomposites was characterised by Raman spectroscopy. The thermal analysis showed that all CPs in the nanocomposites were stable for more than 500°C. Energy diffraction X-ray showed that the amount of Mo in element the PPy(MoO₄)/MMT nanocomposite was 5.55%. The corrosion protection mechanism of the nanocomposites was investigated by electrochemical methods, showing that MMT acted as a barrier layer in nanocomposite and molybdate as an inhibitor for corrosion protection of metal.     

Preparation and characterization of carbon/montmorillonite composites and nanocomposites from waste bleaching sodium montmorillonite clay

Waste bleaching sodium montmorillonite clay was used to prepare carbon/clay nanocomposites and composites by calcination in a reducing atmosphere. The main purpose of this study was to determine the influence of the calcination temperature and solvent washing in the material structure and its adsorption properties. X-ray diffraction patterns detected the nanocomposite formation only in the samples calcinated at 350 °C, whose structures were also described by Fourier transform infrared spectra. SEM images showed that all the samples were composed of various agglutinated grains and the non-washed sample calcinated at 350 °C presented the highest carbon recovery as its surface was the smoothest one, as confirmed by thermogravimetry curve. As a result of this higher carbon content, its methylene blue and gasoline adsorption capacities were the highest, albeit a bit lower in comparison to activated carbon due to the hydrocarbon formation onto sample surface. Finally, BET and BJH studies showed that porosity should also be improved in order to achieve higher adsorption values.     

蒙脱土改性聚丙烯纳米复合材料研究进展

介绍了蒙脱土(MMT)的特性以及MMT改性聚丙烯(PP)的机理,综述了近几年经MMT改性后的PP纳米复合材料在力学性能、结晶性能以及热性能等方面的研究进展,并展望了其发展前景。     

Structure and mechanical properties of polycarbonate modified clay nanocomposites

Polycarbonate (PC)/modified clay nanocomposites were prepared, in the absence and presence of different amounts of maleic anhydride grafted polypropylene (PP-g-MA), by direct melt blending. Their structures, as well as mechanical, morphological and thermal properties, were characterized by X-ray diffractometry (XRD), tensile testing, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The XRD results of the PC/clay nanocomposites showed that they had intercalated structures, although some exfoliation was visible at low clay contents, that the gallery heights of the PC/clay nanocomposites were almost the same, and that some of the clay layers collapsed as a result of modifier decomposition at the high processing temperature. The XRD patterns of the PC/PP-g-MA/clay nanocomposites clearly show less intercalation and more exfoliation with increasing PP-g-MA content. These results were supported by TEM observations. Both the tensile strength and modulus show substantial improvements with both increasing clay and PP-g-MA contents, while the elongation at break substantially decreases, although the presence of PP-g-MA somewhat improves these values. All the nanocomposites have lower thermal stability than pure PC, but the presence of PP-g-MA seems to improve the thermal stability of these samples.     

聚吡咯/凹凸棒石水性导电涂料的制备

用吡咯单体(Py)在凹凸棒石(ATP)的表面发生原位聚合反应,制备出聚吡咯/凹凸棒石(PPy/ATP)纳米导电复合材料.通过Fourier红外光谱、X射线衍射、扫描电子显微镜对复合材料进行表征,结果表明聚吡咯的包覆没有破坏凹凸棒石的晶体结构,两者之间作用仅为物理作用.以PPy/ATP为填料制备的水性丙烯酸涂料导电性高于以PPy为填料制备的水性丙烯酸涂料,并通过SEM研究了涂层的导电机理,表明PPy/ATP在导电涂料中具有更为广阔的应用前景.     

Thermal stability of electrochemically prepared polythiophene and polypyrrole

The degradation behaviour of electrochemically prepared polythiophene and polypyrrole has been studied by thermal gravimetric analysis technique. Studies on both the polymers show that they are more stable than polyacetylene but still undergo degradation reactions which involve two steps, viz. loss of dopant and then degradation of polymer backbone. The general features of degradation mechanisms are discussed.     

Melt processing of polypropylene/clay nanocomposites modified with maleated polypropylene compatibilizers

Maleic anhydride-grafted polypropylene (PPgMA) and organically modified clay composites were prepared in a plasticorder. PPgMAs, including PB3150, PB3200, PB3000, and E43, with a wide range of MA content and molecular weight were used. The structure was investigated with X-ray diffraction (XRD) and transmission electron microscopy (TEM). PPgMA compatibilizers gave rise to similar degree of dispersion beyond the weight ratio of 3 to 1 with the exception of E43, which had the highest MA content and the lowest molecular weight. It was found that thermal instability and high melt index were responsible for ineffective modification by E43. Furthermore, PPgMA with low melting point and high melt index was compounded at low equilibrium temperature in order to maintain a certain level of torque. We then modified polypropylene/organoclay nanocomposites with different levels of PPgMA compatibilizers on a twin-screw extruder. The PP/E43/clay system, as shown through XRD patterns and TEM observation, yielded the poorest clay dispersion among the compatibilizers under investigation. The relative complex viscosity curves also revealed a systematic trend with the extent of exfoliation and showed promise for quantifying the hybrid structure of the nanocomposites. Mechanical properties and thermal stability were determined by dynamical mechanical analysis and thermogravimetric analysis, respectively. Though PPgMA with lower molecular weight and higher MA content could lead to good clay dispersion in PP/clay composites, it caused the deterioration in both mechanical and thermal properties of PP/PPgMA/clay composites.     

Effect of titanate-based surface on hydrophilicity and interlayer spacing of montmorillonite clay for polymer nanocomposites

The fundamental scientific investigations on structure-property correlation of organo-clay are quite valuable in understanding the interface chemistry thus to design and engineer the most effective polymer-clay nanocomposites systems. Organo alkyl-titanate derivatives have been used as reagents for the surface modification of pristine montmorillonite clay platelets. Such surface modification is validated through coordinated characterization techniques that include X-ray photoelectron spectroscopy (XPS), contact angle measurements, X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). By fine-tuning the surface characteristics (controlling the hydrophilicity); effective nanodispersion in polymers by intercalation or delamination can be accomplished. The titanate-coupling agent increased the water contact angle of the clay from 6 to 44 degrees denoting significant decrease in hydrophilicity. Similarly, XRD studies revealed the increased inter-gallery spacing from 9.8 to 12.7 A. The grafting of titanate modifier on to clay surface is quantified through XPS elemental analysis and co-related with TGA. This new surface-modification method provides an effective technique to convert the hydrophilic surface of the montmorillonite clay into organophillic for polymer-clay nanocomposites.     

导电聚合物及导电聚吡咯的研究进展

综述了导电聚合物的发展历史，导电聚合物的结构特征和基础性能、导电聚合物的类型及其合成方法；然后重点介绍了导电聚吡咯的研究进展。     

Ferromagnetic conductive polypyrrole doped with water-soluble ferrocene derivative

In this paper, we report synthesis and characterization of polypyrrole (PPy) doped with a new water-soluble ferrocene derivative of p-ferrocenyl benzene sulfonic acid (BSAFc). The ferromagnetic conductive PPy powder was obtained by chemical polymerization. XPS and FT-IR were used to clarify the structure of PPy powder and confirm the existence of ferrocene group in the PPy powder. A complete understanding of the electronic structure of iron in PPy powder was achieved by Mössbauer spectrum measured at room temperature, which indicates that ⁵⁷Fe in the PPy powder is in the low-spin electronic structure of trivalence. The PPy powder exhibited an electrical conductivity of about 10⁰ S/cm at room temperature, a coercive force of 20 Oe and saturation magnetization of 1.76 emu/g at low temperature of 1.8 K. Thermogravimetric analysis (TGA) showed that the PPy powder had the same thermostability as normal PPy. The electro-active PPy freestanding film was also synthesized by doping with the new water-soluble ferrocene derivative via electrochemical polymerization, which is significant for developing the application of the PPy film in secondary battery, membrane electrode and so on.     

等离子体改性聚吡咯膜共价固定乳酸脱氢酶

采用氨等离子体表面改性聚吡咯,使其表面具有活性氨基,并成功地将具有生物活性的乳酸脱氢酶共价连接在改性聚吡咯表面。用反射红外光谱研究了氨等离子体处理前后聚吡咯及聚吡咯酶多层薄膜的表面微观结构。紫外光谱和循环伏安测试结果证实,表面固定了乳酸脱氢酶的聚吡咯多层薄膜具有生物催化活性和电化学活性,有望作为丙酮酸生物传感器。     

Versatile method for synthesis of electrically conductive polypyrrole-polystyrene clay nanocomposites using ATRP and chemical polymerisation methods

A synthetic route for the preparation of a novel solution copolymer derived from styrene (St), pyrrole (Py) and its organoclay nanocomposite with conductive and mechanical properties is demonstrated. The electroactive copolymer of polystyrene-g-polypyrrole (PSt-g-Ppy) nanocomposite was successfully prepared by atom transfer radical polymerisation (ATRP) and chemical polymerisation methods. First, potassium pyrrole was reacted by α-chlorophenyl acetyl chloride to prepare an initiator that can polymerise styrene by ATRP technique. Then, polypyrrole was prepared by chemical polymerisation using FeCl₃ as an oxidant in dichloromethane^,s solvent. Nanocomposites of the copolymer with modified montmorillonite were prepared with a solution intercalation method. The conductivity of the copolymer was measured by the four-point probe method. The structures of the intermediate, copolymer and nanocomposite were investigated by Fourier transform infrared spectroscopy, ¹H-NMR and X-ray diffraction techniques. The molecular weight of the copolymer was determined by gel permeation chromatography. Their thermal behaviour was examined by differential scanning calorimetry and thermogravimetric analyses.     

Montmorillonite/polypyrrole nanocomposites. The effect of organic modification of clay on the chemical and electrical properties

Montmorillonite/polypyrrole (MMT/PPy) nanocomposites, with 15% mass loading of PPy, were prepared by the in situ polymerization of pyrrole in the presence of montmorillonite (MMT) or organo-modified montmorillonite (oMMT) in aqueous solutions containing an oxidant and an anionic surfactant. The morphology of MMT/PPy nanocomposites distinctly differs from that of the untreated MMT as shown by SEM. X-ray photoelectron spectroscopy showed that the MMT/PPy nanocomposite has an MMT-rich surface, whereas the oMMT/PPy nanocomposite surface has a rather organic nature. Due to the organic modification of MMT by the alkylammonium chloride, polymerization of pyrrole at the surface of oMMT is much more efficient in producing a conductive adlayer resulting in an enhancement of conductivity of the oMMT/PPy nanocomposites (1.1 S cm^− 1) compared to MMT/PPy (3.1 × 10^− 2 S cm^− 1). The difference in the behaviour of oMMT/PPy and MMT/PPy is interpreted in terms of surface energy minimization by the alkylammonium ions present at the surface of organo-modified MMT. Indeed, the dispersive contribution to the surface energy (γ_s^d), as determined by inverse gas chromatography at 150 °C, was estimated to be 34.0 mJ/m² for oMMT, much lower than the value of 216 mJ/m² determined for MMT.     

Thermal properties of ethylene octene copolymer (Engage)/dimethyldioctadecyl quaternary ammonium chloride-modified montmorillonite clay nanocomposites

The nanocomposites of ethylene octene copolymer (Engage^®) with an organically modified (dimethyldioctadecyl quaternary ammonium chloride) montmorillonite (M-MMT) clay were synthesized by using a solution intercalation technique. The intercalation of M-MMT layers for M-MMT loading of 2.5–7.5% was verified by the shift of X-ray diffraction peak to a lower angle, showing change in basal d-spacing from 1.26 for M-MMT to 1.35 nm. Internal structure and the dispersion state of M-MMT in the nanocomposites were observed by transmission electron microscope, which confirmed the clay in the intercalated state. Thermomechanical analysis results showed improved dimensional stability under compression at 30 °C for nanocomposites with increasing M-MMT. By DMA, the storage moduli of nanocomposites below glass transition temperature were higher than the neat Engage and increased with increasing M-MMT content. The glass transition temperature was lowest for the nanocomposite containing 2.5% M-MMT (E-2.5M-MMT), suggesting the optimal concentration of M-MMT in nanocomposite being 2.5% or higher from the viewpoint of thermal properties. The oxidation induction time (OIT) of the nanocomposites was obtained by using pressure-differential scanning calorimeter. The Engage/M-MMT nanocomposites were superior in thermal oxidation resistance as compared to the neat Engage, with E-5.0M-MMT yielding highest OIT_time value.