Thermal properties of processable polyaniline with novel sulfonic acid dopants

Thermal properties of melt processable polyaniline (PANI) synthesized by doping with functionalised novel sulfonic acid dopants have been investigated. Doping of PANI was carried out by using the dopants derived from an inexpensive naturally existing biomonomer, cardanol: sulfonic acid of 3‐pentadecylphenol, sulfonic acid of 3‐pentadecylanisole and sulfonic acid of 3‐pentadecylphenoxyacetic acid. These dopants act as very good plasticizing cum protonating agents for PANI. Doping was carried out either by mechanical mixing of emeraldine base and the dopant or by an in situ doping emulsion polymerization of aniline. Highly conducting free‐standing flexible films of protonated PANI could be prepared by a hot pressing method at different temperatures. The thermal stability and thermal reactions of these protonated PANI were followed by conductivity measurements at different temperatures, wide angle X‐ray diffraction measurements, thermogravimetric analysis and differential scanning colorimetry analysis. © 2001 Society of Chemical Industry     

Studies on the formation of self-assembled nano/microstructured polyaniline–clay nanocomposite (PANICN) using 3-pentadecyl phenyl phosphoric acid (PDPPA) as a novel intercalating agent cum dopant

Novel self-assembled micro/nanostructured polyaniline–clay nanocomposite (PANICN) materials were prepared by in situ intercalative emulsion polymerization of aniline in aqueous dispersion of clay using functionalized amphiphilic dopant, 3-pentadecyl phenyl phosphoric acid (PDPPA) derived from renewable resource. The structural effect of PDPPA on the morphology, electrical conductivity and phase transition temperature of PANICNs was compared with nanocomposites prepared using dodecyl benzene sulphonic acid (DBSA) and HCl. X-ray diffraction and scanning electron microscopic (SEM) studies revealed the formation of monolayer of protonated PANI intercalated nanoclay layers with template polymerized self-assembled micro/nanostructured PANI on the surface of the clay. Nano/microstructured PANIs were formed by the supra-molecular self-assembling of the inter-chain hydrogen bonding, interplane phenyl stacking and electrostatic layer-by-layer self-assembling (ELBS) between polarised alkyl chains present in dopant anions and were manifested using Fourier transform infrared spectroscopy and differential scanning calorimetry.     

Effect of dopant mixture on the conductivity and thermal stability of polyaniline/nomex conductive fabric

Electrically conductive polyaniline (PANI)/[poly(m‐phenylene isophthalamide)] Nomex composite fabric was prepared by in situ polymerization of aniline doped by a mixture of hydrochloride (HCl) and various sulfonic acids such as benzenesulfonic acid (BSA), sulfosalicylic acid (SSA), and dodecylbenesulfonic acid (DBSA); their effect on conductivity and physical properties were then investigated. PANI/Nomex composite fabrics doped by a mixture of protonic acids exhibited higher conductivity than those doped by other single dopants such as camphorsulfonic acid (CSA), p‐toluenesulfonic acid (TSA), BSA, SSA, and HCl. The conductivity of PANI/Nomex fabrics especially doped by a mixture of HCl and DBSA was evenly maintained up to 100°C without depression of mechanical properties of Nomex. Their conductivity was also maintained under extension of the composite fabric. In addition, electrical conductivity of PANI/Nomex fabrics was highly increased by ultrasonic treatment, which facilitated better diffusion and adsorption of aniline by cavitation and vibration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2245–2254, 2002     

Synthesis and studies of exceptionally crystalline polyaniline thin films

Highly crystalline camphor sulfonic acid (CSA)‐doped polyaniline (PANI) thin films cast from m‐cresol and N‐methylpyrrolidone (NMP) were investigated. PANI powder prepared by chemical oxidative polymerization subjected to doping–de‐doping–re‐doping procedures was cast into thin films using NMP and m‐cresol as solvents. X‐ray diffraction (XRD) reveals the presence of exceptionally highly crystalline or rather ordered regions in the PANI film samples prepared from m‐cresol. Atomic force microscopy (AFM) images also support the presence of crystalline regions on the surface of these films. The DC electrical conductivity of m‐cresol‐cast PANI is found to be quite high, and much higher than that of NMP‐cast PANI. The free‐carrier absorption tail extending to the near‐infrared region observed in the optical absorption spectrum of the m‐cresol‐cast PANI films suggests a metallic nature and regular structural arrangement in these films. Both inter‐chain and intra‐chain ordering brought about as a result of CSA doping, secondary doping effect of m‐cresol and ultrasonication are suggested to be the prime factors contributing towards the observed excellent crystallinity of these PANI films as evident from the XRD and AFM studies. The marked thermal stability of the m‐cresol‐cast PANI films is also established based on the variation of DC electrical conductivity with temperature and on thermogravimetric analysis. Copyright © 2012 Society of Chemical Industry     

Synthesis of polyaniline nanofiber and copolymerization with acrylate through in situ emulsion polymerization

Polyaniline (PANI) was prepared, respectively, by direct mixed oxidation method in different acids. Scanning electron microscopy showed that high quality of PANI nanofibers can be obtained easily in hydrochloric acid, sulfuric acid, and acetic acid, especially in the sulfuric acid; infrared and ultraviolet spectra characterization showed all products were the doped PANI. Then, using complex emulsifiers, PANI was dispersed in acrylate emulsion by supersonic dispersion assisted with mechanical stirred to obtain mixed pre‐emulsion, the result showed different PANI performed different dispersing stability in the pre‐emulsion. More importantly, PANI–polyacrylate copolymer was prepared through multi‐steps in situ emulsion polymerization using water‐soluble azo (VA‐044) as initiator. Experiment showed that good dispersing stability of PANI in the pre‐emulsion was premise to obtain the final stable copolymer emulsion. Further, the micro‐morphology and thermal property of the copolymer were studied by transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analyzer. The result proved that acrylate occurred in situ polymerization on surface of PANI nanofibers, the presence of PANI increased glass transition temperature (T_g) and thermal decomposed temperature of the copolymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A novel soluble PANI/TPU composite doped with inorganic and organic compound acid

A series of novel soluble and thermoplastic polyurethane/polyaniline (TPU/PANI) composites doped with a compound acid, which was composed of an organic acid (p‐toluene sulfonic acid) and an inorganic acid (phosphoric acid), were successfully prepared by in situ polymerization. The effect of aniline (ANI) content, ratio of organic acid/inorganic acid, and different preparation methods on the conductivity of the TPU/PANI composites were investigated by using conductivity measurement. Lithium bisoxalato borate (LiBOB) was added to the prepared in situ TPU/PANI to coordinate with the ether oxygen groups originating from the soft molecular chains of TPU, and thus the conductivity of the composites was further enhanced. The molecular structure, thermal properties, and morphology of the TPU/PANI composites were studied by UV–visible spectroscopy, differential scanning calorimetry, and scanning electron microscopy, respectively. The results show that the in situ TPU/PANI composites doped with the compound acid can be easily dissolved in normal solvents such as dimethylformamide (DMF) and 1,4‐dioxane. The conductivity of the TPU/PANI composites increases with the increase of the ANI content, in the ANI content range of 0–20 wt %; however, the conductivity of the composites reduces with further increment of ANI content. The conductivity of the TPU/PANI composites prepared by in situ polymerization is about two orders of magnitude higher than that prepared by solution blending method. LiBOB can endow the in situ TPU/PANI composites with an ionic conductivity. The dependence of the conductivity on temperature is in good accordance with the Arrhenius equation in the temperature range of 20–80°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Doping effect of organic sulphonic acids on the solid‐state synthesized polyaniline

Polyaniline (PANI) salts doped with organic sulfonic acids (methanesulfonicacid, p‐toluenesulphonic acid, and dodecylbenzenesulphonic acid) were first synthesized by using solid‐state polymerization method. The polymers were characterized by Fourier transform infrared (FTIR) spectra, ultraviolet‐visible spectrometry, X‐ray diffraction, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and conductivity measurements. It was found that PANI doped with p‐toluenesulphonic acid is formed in conductive emeraldine oxidation state, and displayed higher doping level and cyrstallinity. On the contrary, PANI doped with dodecylbenzenesulphonic acid was lower at doping level and highly amorphous. In accordance with these results, the conductivity and electrochemical acitivity was also found to be higher in p‐toluenesulphonic acid‐doped PANI, and these properties were opposite in the case of dodecylbenzenesulphonic acid. The results also revealed that the morphology of dodecylbenzenesulphonic acid‐doped PANI was remarkably different from other PANI salts. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Polyaniline/polyimide blends as gas sensors and electrical conductivity response to CO–N2 mixtures

The effects of dopant type, doping level, polyimide (PI) content and temperature on electrical conductivity response of polyaniline (PANI) and polyaniline/polyimide (PANI/PI) blends to CO–N₂ gas mixtures were systematically investigated. At the same doping level, HNO₃‐doped PANI has a greater electrical conductivity response and sensitivity towards CO than that of camphor sulfonic acid (CSA)‐doped PANI because the former has a more ordered structure. The interaction mechanism between CO and PANI is proposed to occur at the attack site, ? N?H? or the amine nitrogen where CO withdraws an electron. Addition of PI causes a small change in electrical conductivity under atmospheric conditions when PI content is below the percolation threshold value of 55 wt%. Addition of PI reduces brittleness and improves electrical conductivity sensitivity towards CO; the effect is more pronounced at higher temperatures. Copyright © 2005 Society of Chemical Industry     

Novel chemically synthesized polyaniline electrodes containing a fluoroboric acid dopant for supercapacitors

The performance of chemically synthesized dual‐acid‐doped polyaniline (PANI) electrode material was investigated for supercapacitors for the first time. Three different grades of PANI‐containing fluoroboric acid (HBF₄) as one of the dopants were prepared by a chemical polymerization method. PANI–dodecylhydrogen sulfate–HBF₄ salt was synthesized by an emulsion polymerization pathway. A PANI–HBF₄–sodium tetrafluoroborate composite and PANI–HBF₄ salt were prepared from different modifications of dopants by a dedoping–redoping process. Capacitative behaviors of the three grades of PANI electrode materials were investigated. Among the three different grades of PANI, PANI–HBF₄ electrode showed the best performance in terms of conductivity (2.3 × 10^?1 S/cm), specific capacitance of the supercapacitor (140 F/g), specific energy (9.6 W h/kg), and specific power (58.8 W/kg). An increase in the capacitance of PANI–HBF₄ was achieved, which identified the significant contribution of the dedoping–redoping processes in the PANI system for supercapacitors. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Epoxidation of modified natural plasticizer obtained from rice fatty acids and application on polyvinylchloride films

In recent years, much research effort has been driven to develop alternative plasticizers for medical and commodity plastic materials. In this study, a modified natural plasticizer, synthesized by esterification of rice fatty acids, was modified by epoxidation with peroxy acid generated in situ. Two natural epoxidized plasticizers were obtained, using peracetic acid (NP‐Ac) and peroctanoic acid (NP‐Oc) as reagent. PVC films after addition of these natural epoxidized plasticizers presented fairly good incorporation and plasticizing performance, as demonstrated by results of mechanical properties, T_g values (as shown by DSC), optical microscopy, exudation, and migration tests, FTIR and X‐ray diffraction obtained for plasticized PVC films. NP‐Ac plasticizer presented enhanced plasticizing performance compared with NP‐Oc, probably due to a higher epoxidation degree obtained in the reaction with peracetic acid. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Melt/solution processable conducting polyaniline: Elastomeric blends with EVA

Polyaniline (PANI) protonated with dopant, the sulfonic acid of 3‐pentadecylphenoxyacetic acid (SPDPAA; synthesized from an inexpensive naturally existing biomonomer, cardanol), was blended with an elastomeric polymer, the ethylene vinyl acetate (EVA) copolymer. Blending was performed either by emulsion polymerization of aniline into the EVA matrix or by the solution‐mixing method. Thin films were prepared by the conventional melt‐processing technique for an emulsion‐polymerized system and by the solution‐casting method for a solution‐mixed system. In the case of the emulsion‐polymerized system, the percolation threshold occurs at a very low weight percentage of PANI, and a maximum conductivity value of 0.85 S cm^?1 was obtained for 28.5 wt % of PANI. These elastomeric conducting blends were characterized by elemental analysis, FTIR and UV‐visible spectral analysis, conductivity measurements, SEM, XRD, tensile properties, TGA, and DSC. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1438–1447, 2002; DOI 10.1002/app.10408     

Electrically conductive polymer blends comprising polyaniline

Summary Electroactive polymer blends comprising polyaniline (PANI) as conductive constituent and poly(methyl methacrylate) (PMMA), polystyrene (PS) and methyl methacrylate-butadiene-styrene (MBS) copolymer as a thermoplastic constituent (TC) were prepared by using various techniques:in situ by oxidative polymerization of aniline in aqueous dispersions of the TC; by, coagulating of latex of TC in the acidic dispersions wherein PANI has been preliminary obtained; and by dry blending. It was shown that highest conductivity values revealedin situ prepared PANI/PMMA blends, where the intermolecular interactions between the constituents were suggested to be stronger than in the other systems studied.     

Novel conducting polyaniline blends with cyanoresin

Novel conducting polyaniline (PANI)/cyanoresin (Cyan) blends were prepared by the addition of Cyan/dimethylformamide solutions to aniline monomer/dopant solutions and the in situ chemical oxidative polymerization of aniline with ammonium persulfate as an oxidant in aqueous p‐toluene sulfonic acid solutions. The PANI/Cyan blends were prepared with various compositions (5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, and 70:30), and blend films of PANI/Cyan were obtained with a casting method. The conductivity of the PANI/Cyan blend films was 10^?7 to 10^?2 S/cm, which was measured by a four‐probe technique. The tensile strength of the blend films was maintained with an increasing amount of PANI (up to 50 wt %), and this was attributed to intermolecular interactions such as hydrogen bonding between PANI and Cyan and a reinforcing effect through blending. This hypothesis was corroborated by Fourier transform infrared spectroscopy. Field emission scanning electron microscopy and thermogravimetric analysis were also used to investigate the morphology and thermal properties of the conducting PANI/Cyan blend films, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1035–1042, 2005     

Systematic evaluation of the preparation of conducting PANI/ABS blends

Films of blended poly(acrylonitrile‐butadiene‐styrene) (ABS) and polyaniline (PANI) were produced by codissolving both components in a common organic solvent, which was then evaporated. The influence of the preparation conditions on the properties of the blends was analyzed by factorial design. The factors evaluated were the PANI content in the blend, the m‐cresol to chloroform solvent ratio, the dopant used (dodecylbenzenesulfonic acid (DBSA) or camphor sulfonic acid) and its concentration, and the acrylonitrile content in the ABS. The responses analyzed were the flexibility and electrical conductivity of the blends. The results showed that the PANI content in the blend and the acrylonitrile content in the ABS were the major factors influencing both of the assessed responses. The dopant affected only the conductivity, DBSA being preferred for the development of more conductive PANI/ABS blends. The solvent ratio did not have any influence, owing to the uniform expanded coil conformation expected for PANI molecules at the studios ratios. After the best conditions had been established, a percolation threshold study was performed that pointed to a low threshold of 3 wt % PANI necessary in the blend, giving a flexible blend with a conductivity of 3 S/cm. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of Ni2+ as a codopant on the structure,morphology, and conductivity of nanostructured polyaniline

One‐dimensional nanostructures of polyaniline (PANI) doped with (1S)‐(+)‐10‐camphorsulfonic acid (D‐CSA) alone and with NiCl₂ as a codopant were synthesized via in situ polymerization. PANI nanofibers with diameters of about 200 nm were formed when PANI was doped with D‐CSA only. When NiCl₂ was added as a codopant, the morphology of PANI obviously changed. The effects and related mechanisms were investigated by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, inductively coupled plasma–atomic emission spectroscopy, and X‐ray diffraction, and the results indicated that Ni²⁺ destroyed the micelles' structure by chemical conjunction with ? SO₃H groups in camphorsulfonic acid (CSA) molecules, which were the key component in forming the CSA–aniline micelles. The combination between Ni²⁺ and SO in CSA with a lower addition of Ni²⁺ led to a reduction of CSA doping to PANI, but a higher loading of Ni²⁺ brought about the direct doping of Ni²⁺ to PANI, which caused a higher degree of doping and oxidation. The conductivity of PANI increased almost linearly with increasing Ni²⁺. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of dopant type on the properties of polyaniline

The comparative study on the effect of different type of dopants on the properties of polyaniline (PANI) is relative less although dopant has profound effect of the properties of PANI. So, the aim of the present work is to study the effect of different type of dopant, namely strong inorganic hydrochloric acid (HCl), organic and aromatic acids containing different aromatic substitution, namely p‐toluene sulfonic acid (PTSA), dodecylbenzenesulfonic acid (DBSA), organic and aliphatic acids having long hydrocarbon chain, namely lauric acid (LA), on the properties of PANI. The PANI was prepared through oxidative polymerization methods and doped with HCl, PTSA, DBSA, and LA and then characterized through different methods like conductivity measurement, UV, X‐ray, DSC, TGA, and SEM. It was found that the properties of doped PANI depend on the type and molecular size of the dopant. With the increase in dopant chain length, the crystallinity is decreased, whereas the d‐spacing, interchain separation, and solubility are increased. The bond formation of water molecules with the backbone nitrogen of the polymers is much less in presence of aromatic dopants when compared with those of inorganic or aliphatic dopants. All the doped polyanilines under investigation do not decompose up to 500°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electrically conductive carbon nanopipe-graphite nanosheet/polyaniline composites

Carbon nanopipe (CNP)–graphite nanosheet (GNS)/polyaniline (PANI) composites are synthesized by in situ chemical oxidative polymerization. The structural analysis (electron microscopy, Raman and X-ray diffraction) reveal that PANI is uniformly coated on both CNP and GNS structures resulting in the formation of a network of uniform composite structures. Thermogravimetric analysis shows that CNP–GNS/PANI composites are thermally stable up to 300 °C; the polymeric backbone degrades above 300 °C. CNP–GNS/PANI composites doped with m-cresol, a mixture of camphor sulfonic acid (CSA) and chloroform, and a mixture of CSA and m-cresol are electrically conductive. The electrical conductivity strongly depends on the dopants and about six orders of variation in conductivity can be achieved through the choice of the dopant.     

Characterizations on the amidized multiwalled carbon nanotubes grafted with polyaniline via in situ polymerization

A multiwalled carbon nanotubes (MWCNTs) were carboxylated after refluxing with sulfuric and nitric acids. These attached carboxylic acid groups were further condensated with o‐phenylene diamine into amide catalyzed by dicyclohexyl carbodiimide (DCC). The obtained amidized MWCNTs were in situ‐polymerized with aniline monomers to graft a conducting polyaniline (PANI) onto MWCNT (ES‐g‐MWCNTs) through the polymerization occurring in the ortho‐ and meta‐positions. The reduced conductivity of the MWCNT after carboxylation can be recovered after grafting with PANI, which owns a strong λ_max at the near infrared region due to the extended conjugation from MWCNTs to PANI. Transmission electronic microscopic pictures show a gradual broadening of the MWCNT diameter after carboxylation, amidization, and polymerization. The weight loss from the thermogravimetric thermograms due to the carboxylations of MWCNTs, amidized MWCNTs, and the PANI grafted MWCNTs into CO₂ can be used to estimate the degree of carboxylation, amidization, and grafting of PANI. The degree of carboxylation of MWCNT calculated from ESCA spectrum is around 23% close to that estimated from TGA thermogram. The doping level of redoped PANI‐grafted MWCNT is found to be 27.78% much less than the maximum 50% of neat PANI. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of microstructural functional polyaniline layers on SPEEK/HPW proton exchange membranes

In this study, a method is developed to fabricate sulfonated poly (ether ether ketone)/phosphotungstic acid‐polyaniline (SPEEK/HPW‐PANI) membranes by in situ polymerization of aniline for the purpose of decreasing the weight loss of HPW in the membranes. The synthesis involves the production of a SPEEK/HPW hybrid membrane followed by different layer of PANI coatings on the membrane surface, and subsequent treatment using drying in vacuum procedures. The scanning electronic microscopy images showed that HPW had good compatibility with SPEEK polymers and energy dispersive X‐ray spectroscopy revealed the successfully doping with HPW and polymerization of PANI. The surface of SPEEK/HPW‐PANI becomes more compact than that of SPEEK/HPW and pure SPEEK, which may lead to reduce the water uptake and swelling property. The proton conductivity was found for the SPEEK/HPW‐PANI‐5 composite membrane (91.53 mS/cm at 80°C) higher than that of pure SPEEK membrane (68.72 mS/cm at 80°C). Better thermal stability was determined in both SPEEK/HPW and SPEEK/HPW‐PANI membranes than pristine SPEEK membrane. Therefore, PANI is a good potential coating for organic–inorganic hybrid e.g. SPEEK/HPW membrane materials to improve their hydrothermal stable properties and SPEEK/HPW PANI is a material that shows promise as a proton exchange membranes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41033.     

Dielectric properties of PANI/PSS blends obtained by in situ polymerization technique

Polyaniline (PANI) was obtained by in situ polymerization in a polystyrene sulfonic acid (PSS) solution. We prepared a series of PANI/PSS blends with molar ratio of 1:2, and PSS sulfonated at the degrees of 13 mol%, 21 mol% and 30 mol%. A control sample of polystyrene, at an intermediate sulfonation degree of 21%, without polyaniline, was also considered. The impedance spectroscopy, scanning electron microscopy and X-ray diffraction of the blends were evaluated. Increasing sulfonation degree increases the conductivity of the blends. Scanning electron microscopy (SEM) images allowed us to correlate the electrical properties of the blends with their morphologic characteristics. The smoothness of the blends surface observed by SEM increased with the sulfonation degree. X-ray diffraction indicated the increasing order with the sulfonation. This can be associated with homogeneous phase distribution, which results in highly conductive material.