Nanocomposites of natural rubber and polyaniline-modified cellulose nanofibrils

Cellulose nanofibrils (CNF) were isolated from cotton microfibrils (CM) by acid hydrolysis and coated with polyaniline (PANI) by in situ polymerization of aniline onto CNF in the presence of hydrochloride acid and ammonium peroxydisulfate to produce CNF/PANI. Nanocomposites of natural rubber (NR) reinforced with CNF and CNF/PANI were obtained by casting/evaporation method. TG analyses showed that coating CNF with PANI resulted in a material with better thermal stability since PANI acted as a protective barrier against cellulose degradation. Nanocomposites and natural rubber showed the same thermal profiles to 200 °C, partly due to the relatively lower amount of CNF/PANI added as compared to conventional composites. On the other hand, mechanical properties of natural rubber were significantly improved with nanofibrils incorporation, i.e., Young’s modulus and tensile strength were higher for NR/CNF than NR/CNF/PANI nanocomposites. The electrical conductivity of natural rubber increased five orders of magnitude for NR with the addition of 10 mass% CNF/PANI. A partial PANI dedoping might be responsible for the low electrical conductivity of the nanocomposites.     

导电聚苯胺与磁性CoFe2O4纳米复合物的合成及其电磁性能

在利用HNO3处理CoFe2O4磁性纳米粒子使其表面离子化、分散性得到改善的基础上, 采用苯胺在其表面原位聚合, 制备了具有电磁功能的聚苯胺(PANI)/CoFe2O4纳米复合物. 借助TEM、XRD、FT-IR、四探针电导率仪和VSM(振动样品磁强计)等分析手段研究了复合物的形貌、结构及其电磁性能. 结果表明, CoFe2O4以25 nm左右的粒子分散于聚苯胺基体中, 被其完全包覆, CoFe2O4与PANI之间存在化学键合作用; 复合物同时具有电性能和磁性能, 其导电率随CoFe2O4含量增加而降低, 饱和磁化强度随之升高, 而矫顽力在所研究的范围内则先增大而后又减小, 且均高于CoFe2O4的矫顽力.     

Conductive Nanocomposites Based on Cellulose Nanofibrils Coated with Polyaniline-DBSA Via In Situ Polymerization

Summary: Cellulose nanofibrils (CNF) were extracted by acid hydrolysis from cotton microfibrils and nanocomposites with polyaniline doped with dodecyl benzenesulphonic acid (PANI-DBSA) were obtained by in situ polymerization of aniline onto CNF. The ratios between DBSA to aniline and aniline to oxidant were varied in situ and the nanocomposites characterized by four probe DC electrical conductivity, ultraviolet-visible-near infrared (UV-Vis - NIR) and Fourier-transform infrared (FTIR) spectroscopies and X-ray diffraction (XRD). FTIR and UV-Vis/NIR characterization confirmed the polymerization of PANI onto CNF surfaces. Electrical conductivity of about 10⁻¹ S/cm was achieved for the composites; conductivity was mostly independent of DBSA/aniline (between 2 and 4) and aniline/oxidant (between 1 and 5) molar ratios. X-ray patterns of the samples showed crystalline peaks characteristic of cellulose I for CNF samples, and a mixture of both characteristic peaks of PANI and CNF for the nanocomposites. Field emission scanning electron microscopy (FESEM) characterization corroborated the abovementioned results showing that PANI coated the surface of the nanofibrils.     

Synthesis and characterization of polyaniline/graphite conducting nanocomposites

A new method for the synthesis of exfoliated graphite and polyaniline (PANI)/graphite nanocomposites was developed. Exfoliated graphite nanosheets were prepared through the microwave irradiation and sonication of synthesized expandable graphite. The nanocomposites were fabricated via the in situ polymerization of the monomer at the presence of graphite nanosheets. The as-synthesized graphite nanosheets and PANI/graphite nanocomposite materials were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis (TGA). The conductivity of the PANI/graphite nanocomposites was dramatically increased over that of pure PANI. TGA indicated that the incorporation of graphite greatly improved the thermal stability of PANI. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1972–1978, 2004     

Microwave absorption studies of polyaniline nanocomposites encapsulating gold nanoparticles on the surface of reduced graphene oxide in the presence of 2-naphthalene sulfonic acid

Polyaniline nanocomposites containing gold nanoparticles (GNPs) attached to the surface of reduced graphene oxide (RGO) were chemically prepared using β-naphthalene sulfonic acid as a dopant. The synthesized composites were characterized using Fourier transform infrared spectroscopy and UV-vis spectroscopy, and their surface morphology and amended crystallinity were determined by scanning electron microscopy and X-ray diffraction, respectively. Further the elemental analysis was also performed to identify the synthesized polymer composites. Complex impedance measurements were performed on the composite samples in the form of films. Sheets prepared by conventional techniques were used to study the microwave absorption properties in the microwave range of 2–12?GHz, and the effects of sample thickness on the microwave absorption were investigated. Experimental results show that the electrical conductivity of the composites increases with increasing concentrations of added GNP-RGO without a percolation threshold.     

Effect of cellulose nanofibers on induced polymerization of aniline and formation of nanostructured conducting composite

Cellulose nanofibers (CNFs), derived from the most abundant and renewable biopolymer, are known as natural one-dimensional nanomaterials because of their high aspect ratio. CNFs also are rich in hydroxyl groups, offering opportunities for functionalization toward development of high-value nanostructured composites. Herein, CNFs were extracted from poplar wood powder by chemical pretreatment combined with high-intensity ultrasonication, and then coated with polyaniline (PANI) through in situ polymerization. The PANI-coated CNFs formed nanostructured frameworks around PANI, thereby conferring the CNF/PANI composite with stability and higher charge transport. The optimum PANI content to achieve maximum conductivity of CNF/PANI composites was determined. The morphology, crystall structure, chemical composition, and conductivity of the samples were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and four-point probe method, respectivily. Our results demonstrated that CNFs can be effective as a template for a flexible and stable conducting polymer to form higher-order nanostructures.     

Hierarchical nanocomposites of polyaniline scales coated on graphene oxide sheets for enhanced supercapacitors

The homogeneous polyaniline–graphene oxide (PANI-GO) nanocomposites were facilely assembled with a redox system in which cumene hydroperoxide (CHP) and iron dichloride (FeCl₂) acted as oxidant and reductant, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that PANI scales coated uniformly on the surface of GO sheets owing to the synergistic effect between the PANI and GO. The obtained PANI-GO nanocomposites exhibited improved electrochemical performance as an electrode material for supercapacitors compared with the pure PANI. The specific capacitance of the PANI-GO nanocomposites was high up to 308.3 F g^?1, much higher than that of the pure PANI with specific capacitance of 150 F g^?1 at a current density of 1 A g^?1 in 2 M H₂SO₄ electrolyte. The Raman and XPS results illustrated that enhanced electrochemical performance might be attributed to the π-π conjugation between the PANI and GO sheets.     

不同质子酸掺杂对银/聚苯胺纳米复合材料结构和导电性的影响

利用紫外光作为辅助条件,在反胶束体系中采用一步双原位法合成了硝酸(HNO3)、对甲基苯磺酸(TSA)和5-磺基水杨酸(SSA)掺杂的银/聚苯胺(Ag/PANI)纳米复合材料.通过对复合材料进行红外光谱(FTIR)、紫外光谱(UV-Vis)、扫描电镜(SEM)、X射线衍射(XRD)和导电性能的测试,研究了不同质子酸对Ag/PANI纳米复合材料结构、形貌和导电性能的影响.测试结果表明,3种酸掺杂制备的Ag/PANI纳米复合材料均为聚苯胺包覆银粒子的核-壳结构.不同的质子酸掺杂会对Ag/PANI纳米复合材料的电性能有重要影响.在3种酸掺杂的复合材料中,TSA掺杂的复合材料的电导率最佳,为215.14 S·cm-1.     

Preparation and electrochemical analysis of graphene/polyaniline composites prepared by aniline polymerization

Polyaniline (PANI)/graphene nanosheet (GNS) composites were prepared by a chemical oxidation polymerization. The morphology, structure, and crystallinity of the composites were examined by scanning electron microscopy, transition electron microscopy, and X-ray diffraction. Electrochemical properties were characterized by cyclic voltammetry in 1 M H₂SO₄ electrolyte. GNS are considered as supporting materials which can provide a large number of active sites. The PANI nanofibers with diameter of 50 nm were homogeneously coated on the surface of GNS. The PANI/GNS composites exhibited a better electrochemical performance than the pure individual components. The PANI/GNS composites showed the highest specific capacitance 923 Fg^?1 at 10 mVs^?1 compared to 465 Fg^?1 for pure PANI and 99 Fg^?1 for GNS.     

Thermal and electrical behaviors of acid functionalized MWCNT/ABC-type triblock copolymer grafted-MWCNT nanocomposites

In this work, ABC-type triblock copolymer grafted onto the surface of the MWCNT/acid functionalized MWCNT (MWCNT-COOH) composites were prepared and the properties of nanocomposites were characterized extensively using differential scanning calorimetry (DSC), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), ac electrical conductivity and dielectrical measurements.

DSC study showed that the glass transition temperatures of the nanocomposites are a some higher than that of the matrix polymer. The increase in oxidized MWCNT in the nanocomposite improved the thermal stability of the composite, according to initial decomposition temperatures. The ac electrical conductivity has increased moderately with increasing frequency, but has increased slowly with increase in the oxidized MWCNT content in the nanocomposites. The electrical conductivity increases slowly with increasing temperature to about the glass transition temperature, then it increases faster. The dielectric constants for the matrix polymer and all the composites decreases slightly with increasing frequency from 0.1 kHz to 2.0 kHz. The dielectric constant increases slightly with increasing temperature up to about the glass transition temperature region and then the increase in temperature is accelerated the increase in the dielectric constant.     

Electrical conductivity and dielectric constant measurements of liquid crystal–gold nanoparticle composites

The behaviour of the anisotropic electrical conductivity of liquid crystal–gold nanoparticle (LC‐GNP) composites consisting of a commercially available room temperature nematic compound doped with alkylthiol‐capped GNPs has been investigated. The nematic–isotropic transition of the composite decreases nearly linearly with increasing X, the concentration of GNP (in weight %) at a rate of about 1°C /weight %. The inclusion of GNPs increases the electrical conductivity of the system with the value increasing by more than two orders of magnitude for X = 5%. However, the anisotropy in conductivity, defined as the ratio of the conductivity along (σ_∥) and orthogonal (σ_⊥) to the director shows a much smaller but definite decrease as X increases.     

Coating of multiwalled carbon nanotubes with polymer nanospheres through microemulsion polymerization

We report a simple and noncovalent method for coating multiwalled carbon nanotubes (MWCNTs) with polyaniline (PANI) nanospheres using a microemulsion polymerization method. In this method, aniline polymerization is performed with MWCNTs in the presence of sodium dodecyl sulfate (SDS), which serves as both a surfactant and a dopant. Morphological, structural, thermal, and electrical properties of MWCNT–PANI nanocomposites were analyzed. The TEM results of the nanocomposites prepared with surfactant reveal that 30–50-nm-diameter PANI nanospheres were coated on the surface of the MWCNTs. Composites prepared without surfactant were found to be in core–sheath-type cable structures. The conductivities of the nanocomposites synthesized through microemulsion polymerization were found to be one order of magnitude higher than both the conductivities of pure PANI and the composites prepared via in situ chemical polymerization without an assisting SDS surfactant. The mechanism for the formation of nanostructured composites is presented.     

The Electrochemical Properties of Nanocomposite Films Obtained by Chemical In Situ Polymerization of Aniline and Carbon Nanostructures

Interactions between the π bonds in the aromatic rings of polyaniline (PANI) with carbon nanostructures (CNs) facilitate charge transfer between the two components. Different types of phenyleneamine‐terminated CNs, including carbon nano‐onions (CNOs) and single‐walled and multi‐walled carbon nanotubes (SWNTs and MWNTs, respectively), were prepared as templates, and the CN/PANI nanocomposites were easily prepared with uniform core–shell structures. By varying the ratio of the aniline monomers relative to the CNs in the in situ chemical polymerization process, the thickness of the PANI layers was effectively controlled. The morphological and electrical properties of the nanocomposite were determined and compared. The thickness and structure of the PANI films on the CNs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and infrared spectroscopy. TEM and SEM revealed that the composite films consisted of nanoporous networks of CNs coated with polymeric aniline. The electrochemical properties of the composites were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. These studies showed that the CN/PANI composite films had lower resistance than pure polymeric films of PANI, and the presence of CNs much improved the mechanical stability. The specific electrochemical capacitance of the CNO/PANI composite films was significantly larger than for pure PANI.     

Cerium dioxide/polyaniline core-shell nanocomposites

The preparation of CeO2/polyaniline (CeO2/PANI) core-shell nanocomposites via chemical oxidation of aniline using CeO2 as an oxidant is reported. TEM, TGA, FT-IR, XPS, and conductivity measurement are used to characterize the resulting composites. TEM measurements reveal that the shape of PANI/CeO2 nanocomposites is different from CeO2 nanoparticles and fibular PANI oxidized with soluble oxidant. Electron diffraction (ED) patterns of CeO2/PANI nanocomposites reveal single crystal of CeO2. FT-IR spectra confirmed the formation of PANI; the amount of PANI in the nanocomposites is estimated by TGA results. The conductivities increase with the increasing ratio of PANI/CeO2. XPS results reveal that in the nanocomposites Ce4+ of CeO2 is reduced to Ce3+. In addition, the degree of protonation of polyaniline obtained from N 1s XPS results in cerium dioxide/polyaniline composites is about 48.52%.     

Immobilization of gelatin onto natural nanofibers for tissue engineering scaffold applications without utilization of any crosslinking agent

Bacterial cellulose was oxidized by periodate oxidation to give rise to 2,3-dialdehyde bacterial cellulose (DABC) with 60.3 ± 0.5 % aldehyde content, which was further reacted with gelatin (Gel) for the immobilization of Gel to form DABC/Gel nanocomposites. The scanning electron microscopy and transmission electron microscopy revealed that DABC/Gel exhibited the refined 3D nano-network structures and the average thickness of Gel coatings in the composites was about 75 nm. FTIR and XPS were utilized to analyze the functional groups and chemical states of DABC/Gel nanocomposites. The results inferred that Gel was fixed on DABC nanofibers via the Schiff base reaction between –NH₂ in Gel and –CHO in DABC backbone. NIH3T3 mice fibroblast cells were used for determining the cytocompatibility of the scaffolds. The morphology of the cells was observed through optical inverted microscopy. The results show that DABC/Gel can be used as scaffold material in tissue engineering.     

Synthesis and characterization of C60/polyaniline composites from interfacial polymerization

C₆₀/polyaniline (PANI) nanocomposites have been synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in the presence of C₆₀ by using an interfacial reaction. When compared with the pure PANI nanofibers from the similar process, the diameter of the obtained C₆₀/PANI nanofibers was increased because of the encapsulation of C₆₀ into PANI during aniline polymerization, which resulted from the charge‐transfer interactions between C₆₀ and aniline fragment in PANI. In addition, the resulting C₆₀/PANI nanocomposites synthesized from the low initial C₆₀/aniline molar ratio (less than 1:25) showed the homogenous morphology composed of fiber network structures, which has an electrical conductivity as high as 1.1 × 10^?4 S/cm. However, the C₆₀/PANI nanocomposites from the higher initial C₆₀/aniline molar ratio (more than 1:15) showed the nonuniformly distributed morphology, and the electrical conductivity was decreased to 3.5 × 10^?5 S/cm. Moreover, the C₆₀/PANI nanocomposites from the interfacial reaction showed a higher value of electrical conductivity than the mechanically mixed C₆₀/PANI blends with the same C₆₀ content, because of the more evenly distributed microstructures. FTIR, UV–vis, and CV data confirmed the presence of C₆₀ and the significant charge‐transfer interactions in the resultant nanocomposites, which was responsible for the morphology development of the C₆₀/PANI and the variation of the electrical conductivity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Graphene oxide-modified polyaniline pigment for epoxy based anti-corrosion coatings

In the present work, a set of polyaniline–graphene oxide (PANI–GO) nanocomposites which exhibit superior properties in terms of shelf life, processability and conductivity due to the synergistic effect of GO and PANI, have been synthesized by varying the concentration of highly non-conducting GO with respect to aniline. The obtained materials were characterized by UV–Vis, FTIR, XRD, Raman, TGA as well as FESEM, TEM analysis. The results reveal that nanocomposites show better dispersibility, crystallinity, thermal stability, and conductivity. Further, the synthesized composites have been tested for their anti-corrosion properties. The potentiodynamic results reveal that PANI nanocomposites with 1% GO exhibited long-term anti-corrosion behavior with a corrosion rate of 6.5 × 10^?5 mm year^?1, which is much lower than its individual components and commercial-grade red oxide. Also, it possesses highest impedance modulus ~33 kΩ cm² and real impedance ~32 kΩ cm², maximum coating resistance ~14.81 × 10³ Ω cm² and minimum coating capacitance after 96 h of immersion in 3.5% mass NaCl than those exhibited by all other coated samples. Higher concentration of GO could not retard the corrosion rate confirming that hydrophilicity of GO play an important role in the redox mechanism of PANI.     

Changes During Storage of Electrically Conductive Blends Polyaniline–Poly(Ethylene‐co‐vinyl Acetate)

Abstract

The electrical conductivity behavior of polyaniline–poly(ethylene‐co‐vinyl acetate) (PANI–EVA) blends was variable and dynamic during their storage. It was shown that the apparent concentration of the intrinsically conductive polymer at which a conductivity jump of the blends occurs (Φ _c ) is not a constant value over time. The electrical conductivity of the films of low PANI content (below 2.5 wt.%) increased by several (ca. 5) orders of magnitude. It was found that the PANI phase undergoes a flocculation process subsequently resulting in the formation of conductive pathways and a continuous network. Besides, the shape of percolation curves was found to change during storage of the films. Decreased conductivity deviations were registered for blends of low PANI content (<2.5 wt.%), indicating that an improvement (or decreasing number of defects) of the conductive pathways took place within the bulk of the insulating EVA matrix. These results and observed phenomena are discussed by means of the interfacial model for electrically conductive polymer blends. They supported the dispersion/flocculation phase transition within similar composite materials. The phase separation and conductivity jump are attributed to the interfacial interactions between the polymeric constituents. It was shown that the microstructure of the blends consists of highly ordered PANI paths embedded in the insulating EVA matrix. Long fibrils of PANI and interconnected fractal‐like networks were observed. It was found that the sizes of the PANI domains also varied during storage of the films. Due to the spontaneous flocculation of the primary PANI particles, conductive pathways are formed at extremely low percolation threshold (Φ _c , loading level ca. 5 × 10^?3 wt. fraction). Thus, an important property of the conductive constituent, namely its solid‐state rearrangement, was proved. This PANI self‐organization is also interpreted according to the interfacial model of polymer composites. On the other hand, the competition between self‐organization of the complex of PANI with dodecylbenzenesulfonic acid and crystallization of EVA matrix has resulted in structural changes and formation of continuous conductive networks within the blends, responsible for their significantly increased conductivity.     

Facile synthesis of highly conductive polyaniline/graphite nanocomposites

A facile process for the synthesis of exfoliated graphite and polyaniline/graphite (PANI/graphite) nanocomposite was developed. Graphite nanosheets were prepared via the microwave irradiation and sonication from synthesized expandable graphite. The nanocomposites were fabricated via in situ polymerization of aniline monomer in the presence of graphite nanosheets. The nanoscale dispersion of graphite sheets was evidenced by the SEM and TEM examinations. According to the electrical conductivity test, the conductivity of the final PANI/graphite nanocomposites were dramatically increased compared with pristine PANI. From the thermogravimetric analysis, the introduction of graphite exhibits a beneficial effect on the thermal stability of PANI.     

Polyanilme-montmorilltonite (PANl-MMT) nanocomposites: Mechanochemical synthesis,structure, thermostability and electrical properties

Polyaniline (PANI)-montmorillonite (MMT) nanocomposites were prepared by direct intercalation of aniline molecules into MMT galleries, followed by in situ mechanochemical polymerization under solvent free conditions. X-rays diffraction, Fourier Transform Infra Red analyses and UV-vis spectroscopy confirmed the successful synthesis of polyaniline chains between the MMT nano-interlayers. On increasing the amount of MMT basal spacing decreased gradually, suggesting less intercalation with decreasing amount of aniline. Scanning electron micrographs demonstrated strong differences between the morphologies of PANI-MMT nanocomposites and those of pure MMT and PANI. DC conductivity was measured in the temperature range from 145 K to 303 K using four probe methods. Temperature dependent DC conductivity of PANI and all the PANI-MMT composites followed 3 dimensional variable range hopping (3D VRH) model. Frequency dependent AC conductivity (σ_AC), dielectric constant (ɛ′) and loss factor (ɛ″) have been measured in the frequency range 10²–10⁶. All these measured quantities; σ_AC, ɛ′ and ɛ″ decreased with the increase in MMT content in the composites at all frequencies. The frequency dependence of σ_AC displayed a low frequency region below 10⁴ Hz with almost constant conductivity, while above this frequency a rapid rise in σ_AC was observed with a power law of frequency dependence with an exponent equal to 0.7. Both real and imaginary parts of the permittivity exhibited a low frequency dispersion which has been attributed to hopping of polarons and bipolarons in PANI and its composites. The thermal stability was checked by thermogravimetric analysis (TGA) and was found to be enhanced due to addition of MMT in the PANI.