Colloidal Polyaniline Research Articles

Synthesis and Characterization of Polyaniline Emeraldine Salt (PANI-ES) Colloids Using Potato Starch as a Stabilizer to Enhance the Physicochemical Properties and Processability.

Conductive polymers, such as polyaniline (PANI), have interesting applications, ranging from flexible electronics, energy storage devices, sensors, antistatic or anticorrosion coatings, etc. However, the full exploitation of conductive polymers still poses a challenge due to their low processability. The use of compatible stabilizers to obtain dispersible and stable colloids is among the possible solutions to overcome such drawbacks. In this work, potato starch was used as a steric stabilizer for the preparation of colloidal polyaniline (emeraldine salt, ES)/starch composites by exploiting the oxidative polymerization of aniline in aqueous solutions with various starch-to-aniline ratios. The polyaniline/starch bio-composites were subjected to structural, spectroscopic, thermal, morphological, and electrochemical analyses. The samples were then tested for their dispersibility/solubility in a range of organic solvents. The results demonstrated the formation of PANI/starch biocomposites with a smaller average size than starch particles, showing improved aqueous dispersion and enhanced solubility in organic solvents. With respect to previously reported PANI-EB (emeraldine base)/starch composites, the novel colloids displayed a lower overall crystallinity, but the conductive nature of PANI-ES enhanced its electrochemical properties, resulting in richer redox chemistry, particularly evident in its oxidation behavior, as observed through cyclic voltammetry. Finally, as proof of the improved processability, the colloids were successfully integrated into a thin polyether sulfone (PES) membrane.

Synthesis and characterization of antimicrobial colloidal polyanilines

The potential application of colloidal polyaniline (PANI) as an antimicrobial is limited by challenges related to solubility in common organic solvents, scalability, and antimicrobial potency. To address these limitations, we introduced a functionalized PANI (fPANI) with carboxyl groups through the polymerisation of aniline and 3-aminobenzoic acid in a 1:1 molar ratio. fPANI is more soluble than PANI which was determined using a qualitative study. We further enhanced the solubility and antimicrobial activity of fPANI by incorporating Ag nanoparticles onto the synthesized fPANI colloid via direct addition of 10 mM AgNO3. The improved solubility can be attributed to an approximately 3-fold reduction in size of particles. Mean particle sizes are measured at 1322 nm for fPANI colloid and 473 nm for fPANI-Ag colloid, showing a high dispersion and deagglomeration effect from Ag nanoparticles. Antimicrobial tests demonstrated that fPANI-Ag colloids exhibited superior potency against Gram-positive Staphylococcus aureus, Gram-negative Escherichia coli, and Bacteriophage PhiX 174 when compared to fPANI alone. The minimum bactericidal concentration (MBC) and minimum virucidal concentration (MVC) values were halved for fPANI-Ag compared to fPANI colloid and attributed to the combination of Ag nanoparticles with the fPANI polymer. The antimicrobial fPANI-Ag colloid presented in this study shows promising results, and further exploration into scale-up can be pursued for potential biomedical applications.

Synthesis and Characterization of a Novel Nanosized Polyaniline.

Polyaniline (PANI) is a conductive polymer easily converted into a conducting state. However, its limited mechanical properties have generated interest in fabricating PANI composites with other polymeric materials. In this study, a PANI-prevulcanized latex composite film was synthesized and fabricated in two phases following chronological steps. The first phase determined the following optimum parameters for synthesizing nanosized PANI, which were as follows: an initial molar ratio of 1, a stirring speed of 600 rpm, a synthesis temperature of 25 °C, purification via filtration, and washing using dopant acid, acetone, and distilled water. The use of a nonionic surfactant, Triton X-100, at 0.1% concentration favored PANI formation in a smaller particle size of approximately 600 nm and good dispersibility over seven days of observation compared to the use of anionic sodium dodecyl sulfate. Ultraviolet-visible spectroscopy (UV-Vis) showed that the PANI synthesized using a surfactant was in the emeraldine base form, as the washing process tends to decrease the doping level in the PANI backbone. Our scanning electron microscopy analysis showed that the optimized synthesis parameters produced colloidal PANI with an average particle size of 695 nm. This higher aspect ratio explained the higher conductivity of nanosized PANI compared to micron-sized PANI. Following the chronological steps to determine the optimal parameters produced a nanosized PANI powder. The nanosized PANI had higher conductivity than the micron-sized PANI because of its higher aspect ratio. When PANI is synthesized in smaller particle sizes, it has higher conductivity. Atomic force microscopy analysis showed that the current flow is higher across a 5 µm2 scanned area of nanosized PANI because it has a larger surface area. Thus, more sites for the current to flow through were present on the nanosized PANI particles.

A New Method to Prepare Stable Polyaniline Dispersions for Highly Loaded Cathodes of All-Polymer Li-Ion Batteries.

A new method for the preparation of polyaniline (PANI) films that have a 2D structure and can record high active mass loading (up to 30 mg cm-2) via acid-assisted polymerization in the presence of concentrated formic acid was developed. This new approach represents a simple reaction pathway that proceeds quickly at room temperature in quantitative isolated yield with the absence of any byproducts and leads to the formation of a stable suspension that can be stored for a prolonged time without sedimentation. The observed stability was explained by two factors: (a) the small size of the obtained rod-like particles (50 nm) and (b) the change of the surface of colloidal PANI particles to a positively charged form by protonation with concentrated formic acid. The films cast from the concentrated suspension were composed of amorphous PANI chains assembled into 2D structures with nanofibrillar morphology. Such PANI films demonstrated fast and efficient diffusion of the ions in liquid electrolyte and showed a pair of revisable oxidation and reduction peaks in cyclic voltammetry. Furthermore, owing to the high mass loading, specific morphology, and porosity, the synthesized polyaniline film was impregnated by a single-ion conducting polyelectrolyte-poly(LiMn-r-PEGMm) and characterized as a novel lightweight all-polymeric cathode material for solid-state Li batteries by cyclic voltammetry and electrochemical impedance spectroscopy techniques.

In vitro biocompatibility screening of a colloidal gum Arabic-polyaniline conducting nanocomposite

Although polyaniline (PANI) is a widely investigated conductive polymer for biological applications, studies addressing the biocompatibility of colloidal PANI dispersions are scarcely found in the literature of the area. Therefore, PANI nanoparticles stabilized by the natural polysaccharide gum Arabic (GA) were screened for their biocompatibility. The GA successfully stabilized the colloidal PANI-GA dispersions when exposed to a protein-rich medium, showing compatibility with the biological environment. The results obtained from a series of in vitro assays showed that, after up to 48 h of exposure to a range of PANI-GA concentrations (1–50 μg/mL), both mouse BALB/3T3 fibroblasts and RAW 264.7 macrophages showed no evidence of change in cellular proliferation, viability and metabolic activity. An increase in macrophage granularity poses as evidence of phagocytic uptake of PANI-GA, without resulting activation of this cell type. Additionally, the PANI-GA nanoparticles modulated the cell morphology changes induced on fibroblasts by GA in a concentration-dependent manner. Thus, this unprecedented biocompatibility study of PANI nanoparticles stabilized by a plant gum exudate polysaccharide showed promising results. This simple biomaterial might be further developed into colloidal formulations for biological and biomedical applications, taking advantage of its versatility, biocompatibility, and conductive properties.

Electrophoretic Deposition of Polyaniline on a Copper Substrate and its Application in Corrosion Resistance

Polyaniline (PANI) was prepared by chemical oxidation of aniline for formation of stable colloidal suspension. The suspension was prepared by dispersion of PANI/HCOOH stock solution into acetonitrile. The stable suspension of positively charged PANI colloids was deposited by applying electrophoretic technique on the surface of copper sheet. The coatings obtained were adherent to the copper substrate. The effect of operating parameters such as the deposition time, the concentration of solids in the colloidal suspension, and the voltage applied were examined on the deposition efficiency. The efficacy of the coated layer in corrosion resistance was evaluated using potentiodynamic (Tafel) polarization with a scan rate of-500 to +500 mV. The annealed PANI coated layer showed the highest corrosion efficiency of 86.5% followed by the normal PANI coated layer with inhibition efficiency of 84.4%. The mean roughness and the 3-D morphology of the obtained coated layers from the Atomic Force Microscopy (AFM) were used to explain the surface energy of the coated layers. The rms values obtained for bare copper, annealed PANI coated layer, and the normal PANI coated layer were 63 nm, 182 nm, and 254 nm respectively. The characteristics of the coated surface were examined using Scanning Electron Microscopy (SEM) which indicated a porous layer on the surface of the copper. The crystallographic structure of the coated layers were examined using XRD.

Polyaniline colloids stabilized with bioactive polysaccharides: Non-cytotoxic antibacterial materials

Colloidal polyaniline dispersions stabilized with biocompatible polysaccharides, sodium hyaluronate and chitosan (both with two different molecular weights), were successfully formulated. The colloids were characterized by UV–vis spectra, particle-size distributions and morphology, as well as by their biological properties in terms of cytotoxicity and antibacterial activity. Colloids containing both chitosan and hyaluronate showed only mild cytotoxicities, which were mainly governed by the concentration of conducting polyaniline in the colloid. Antibacterial activity of the samples, however, depended both on the type of polysaccharide and the ratio between the stabilizer and polyaniline mass. The colloid synthetized using 0.2 M aniline hydrochloride, 0.1 M ammonium persulfate, and 1 wt.% sodium hyaluronate of molecular weight of 1.8–2.1 × 106 exhibited the highest antibacterial activity against both gram positive and gram negative bacteria. This formulation, therefore, allowed for the formation of potentially stimuli-responsive antibacterial colloidal particles with low cytotoxicity.

Engineering the poly(vinyl alcohol)-polyaniline colloids for high-performance waterborne alkyd anticorrosion coating

The ecofriendly waterborne alkyd coatings generally compromise the coating performance. Incorporation of polyaniline into alkyd to form nanocomposites can improve the corrosion resistance; however, the uniform distribution of polyaniline (PANI) within the alkyd resin remains a challenge. In this work, PANI is grafted onto epoxy functionalized phosphorylated poly (vinyl alcohol) (PPVA) with different side-chain configurations in order to improve compatibility and dispersion stability. These functionalized PPVA are synthesized using epichlorohydrin (ECIP) or γ-glycidyl methacrylate (GMA) as modifying agents, and respectively labeled as E-PPVA and G-PPVA. G-PPVA/PANI dispersion is stable even at a high PANI loading of 50%, while the maximum PANI loading for E-PPVA/PANI is only 30%. With the incorporation of G-PPVA/PANI into waterborne alkyd resins (AR), the coating resistance is increased by 7 orders of magnitude, and the corrosion inhibition efficiency is up to 99.9%. The coating with the incorporation of G-PPVA/PANI also demonstrates superior long-term corrosion resistance in comparison with that AR/E-PPVA/PANI nanocomposite coating.

Conducting polymer colloids, hydrogels, and cryogels: common start to various destinations

When a conducting polymer, polyaniline, is prepared in the aqueous solutions of poly(vinyl alcohol), it is obtained as a colloidal dispersion of submicrometer particles. When the reaction mixture is frozen before the oxidation of aniline takes place, polyaniline is produced in ice, and a cryogel results after thawing. This technique of conducting hydrogel preparation has been reported only recently. It is newly demonstrated, that colloidal hydrogels are obtained after freezing of colloidal dispersions. Finally, the cryogenic preparation of polyaniline in polyaniline colloids combines latter two techniques of hydrogel preparation to generate a dispersion cryogel. It is thus illustrated that, by using a simple initial system, various macroporous-conducting hydrogels differing in morphology, conductivity, and mechanical properties can be achieved.

Using Polymer Semiconductors and a 3-in-1 Plastic Electronics STEM Education Kit To Engage Students in Hands-On Polymer Inquiry Activities

To improve polymer education for 9–12 and undergraduate students, a plastic electronics laboratory kit using polymer semiconductors has been developed. The three-module kit and curriculum use polymer semiconductors to provide hands-on inquiry activities with overlapping themes of electrical conductivity, light emission, and light-harvesting solar energy conversion. Many of these themes are critical to contemporary polymer molecular electronics research. The kit includes modules to synthesize and evaluate the electrical properties of conductive colloidal polyaniline (PAni), to construct a polymer light-emitting diode using poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), and to build a polymer solar cell using MEH-PPV and nanoparticulate TiO2. Designed initially for high school science classrooms, the activities developed also meet new ACS undergraduate education requirements for macromolecular, supramolecular, and nanoscale systems in the curriculum and can be used in undergraduate tea...

Biological properties of printable polyaniline and polyaniline–silver colloidal dispersions stabilized by gelatin

The oxidation of aniline with ammonium peroxydisulfate in the presence of gelatin yields spindle-like colloidal polyaniline particles having the particle size smaller than 200nm. The similar oxidation of aniline with silver nitrate leads to hybrid composite polyaniline–silver nanoparticles with more complex morphology. The composites were characterized by transmission electron microscopy, dynamic light scattering and UV–vis spectroscopy. The cytoxicity of colloids has also been investigated. To test biointerface properties, the synthetized colloids were deposited to poly(ethylene terephthalate) foil using spiral bar coating and flexography printing technique. Prepared layers were tested for eukaryotic cell adhesion and proliferation, and antibacterial activity. The prepared surfaces do not only allow for eukaryotic cell adhesion and proliferation but also they possess significant antibacterial properties against Escherichia coli and Staphylococcus aureus, even without silver nanoparticles. This newly prepared surface has therefore high practical potential in variety of application in regenerative medicine or biosensing.

Charge transport and contact resistance in coplanar devices based on colloidal polyaniline dispersion

ABSTRACTThe charge transport properties of thin films prepared from colloidal dispersion of polyaniline stabilized by poly(N‐vinylpyrrolidone) (PANI/PVP) have been investigated. The electrical characterization of coplanar device comprising of gold electrodes and PANI/PVP film deposited by spin coating served to gain insights into the contact and bulk resistance. The films prepared from PANI/PVP colloidal dispersion show high stability over a large temperature range. Temperature dependent measurements in the range from 90 to 350 K reveal that the charge transport can be described by a three‐dimensional variable‐range hopping mechanism as the dominant mode in the films. The stability of the films cast from dispersion within a large temperature range opens the possibility of the application as a polymer semiconductor layer in sensors and charge‐transport interlayer in organic solar cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1710–1716

Effect of polyvinylpyrrolidone on storage stability, anti-oxidative and anti-bacterial properties of colloidal polyaniline

Aqueous dispersions of colloidal polyaniline (PANI) were prepared by different methods using a water soluble polymer polyvinylpyrrolidone (PVP) acting as a steric stabilizer. In one of the cases, dispersion was prepared by synthesizing PANI in situ in PVP solution. In another case, PVP-PANI fiber scaffold was prepared by electrospinning and then the electrospun fiber scaffold was dispersed in distilled water. Direct dispersion of PANI in distilled water and aqueous PVP solution were also prepared for comparative studies. Storage stability, anti-oxidant capacity and anti-bacterial efficacies of these dispersions were evaluated. The aggregation between PANI particulates was significantly reduced by using PVP as the dispersing medium. Oxidation state of PANI in these dispersions and the hydrodynamic diameter of the colloidal particles were found to be the critical factors in determining the free radical scavenging capacity and antibacterial activity. Amongst these different PVP based dispersions, the direct dispersion of PANI in PVP solution was the simplest method to produce the colloidal PANI and showed the best free radical scavenging capacity, good antibacterial efficacies as well as storage stability.

Gravure-printed ammonia sensor based on organic polyaniline colloids

A chemoresistive ammonia sensor with sensitive polyaniline layer has been fabricated by gravure printing on flexible poly(ethylene terephthalate) substrate. Novel colloids of polyaniline hydrochloride, which were synthetized in xylene or chloroform in the presence of surfactant, were used as a printing formulation. The sensor characteristics of the colloid-based sensitive layers were compared with in-situ polymerized layers of polyaniline. The colloid-based sensors showed a good response to ammonia concentrations in the range from hundreds of ppb to tens of ppm. This provides an opportunity to use these sensors for both monitoring of maximum exposure limits for humans in workplaces as well as environmental air-pollution. Therefore, these fully printed, metal-free, low cost and flexible ammonia sensors based on organic materials can be used in detection systems for monitoring of hazardous gases.

Heat transfer intensification using polyaniline based nanofluids: Preparation and application

The present work reports on the use of ultrasound assisted emulsion polymerization for the synthesis of polyaniline (PANI) nanoparticles. The study of heat transfer characteristics of PANI based nanofluids at different loading (0–1.2wt%) of PANI nanoparticles in water (reference fluid) was performed at fixed Reynolds number. The heat transfer coefficient enhancement was also studied at two different Reynolds numbers by keeping loading of PANI in the range of 0.2–1.2wt%. The heat transfer performance of PANI nanofluid was studied in a copper tube under constant heat flux conditions. The results showed that the heat transfer coefficient increases with an increase in the colloidal PANI concentration and Reynolds number. For 0.2wt% PANI nanofluids, 33% increment in heat transfer coefficient was observed while it was 63% for 1.2wt% addition of PANI nanoparticles.

Colloidal polyaniline dispersions: Antibacterial activity, cytotoxicity and neutrophil oxidative burst

Polyaniline colloids rank among promising application forms of this conducting polymer. Cytotoxicity, antibacterial activity, and neutrophil oxidative burst tests were performed on cells treated with colloidal polyaniline dispersions. The antibacterial effect of colloidal polyaniline against gram-positive and gram-negative bacteria was most pronounced for Bacillus cereus and Escherichia coli, with a minimum inhibitory concentration of 3500μgmL−1. The data recorded on human keratinocyte (HaCaT) and a mouse embryonic fibroblast (NIH/3T3) cell lines using an MTT assay and flow cytometry indicated a concentration-dependent cytotoxicity of colloid, with the absence of cytotoxic effect at around 150μgmL−1. The neutrophil oxidative burst test then showed that colloidal polyaniline, in concentrations <150μgmL−1, was not able to stimulate the production of reactive oxygen species in neutrophils and whole human blood. However, it worked efficiently as a scavenger of those already formed.

Gas sensing of colloidal polyaniline in a chemoresistor consisting of nanometer electrodes

Abstract The high conductivity of colloid-conducting polymers is explained by the networking structures and the hopping mechanisms of the metallic particles [1] , [2] , [4] . To observe how the metallic region and the networking structures differ in sensing NH3 gas, E-beam lithography and electromigration were used to make chemoresistors with nanometer-gap electrodes. Colloid Pani was coated on a nanometer gap as a reaction matrix for the gas. The I–V curves were measured in a vacuum and the NH3 gas was nonlinear. In sensors with a gap of less than 10 nm, there was a two- or threefold increase in the conductivity, and the work function decreased from 600 meV in a vacuum to 250 meV in NH3 gas. In contrast, the conductivity of sensors with gaps of 200 and 500 nm decreased to 1/1000 in the NH3 gas environment. The decrease of the conductivity can be explained by electron–hole annihilation, which appears to occur on the surface of the secondary particles. With comb-type electrodes, the operating voltage can be decreased by three orders of magnitude. In electrodes with 200 and 500 nm gaps, the I–V has a step-type response to NH3 gas.

Photosensitive polyaniline colloidal particles prepared by enzymatic polymerization using the azopolymer DMA- co-AZAAm as stabilizer

Water-dispersible polyaniline colloids with photosensitivity were prepared by enzymatic polymerization using the photo- and temperature-responsive azopolymer: N, N-dimethylacrilamide (DMA)- co- N-4-phenylazo-phenylacrylamide (AZAAm) copolymer, poly(DMA- co-AZAAm), as steric stabilizer. The resulting polyaniline nanoparticles showed an interesting photoisomerization behavior in water solution, as indicated by 1H NMR and UV–vis spectra obtained after irradiation with UV light at 365 nm. Its comparative analysis with poly(DMA- co-AZAAm) was realized. The effect of the steric stabilizer on the morphology of the polyaniline was studied by AFM and SEM analysis of the polyaniline synthesized with and without azopolymer. Additional characterization such as molecular weight and infrared spectra were performed.

The carbonization of colloidal polyaniline nanoparticles to nitrogen‐containing carbon analogues

AbstractThe carbonization of nanostructures afforded by conducting polymers represents a new route to the preparation of functional nanostructured carbons. The exposure of colloidal polyaniline particles stabilized with poly(N‐vinylpyrrolidone) or silica nanoparticles at 650 °C in inert atmosphere led, in both cases, to nitrogen‐containing carbonaceous materials with specific surface areas of 200 and 205 m2 g−1, respectively, and conductivities of 8.3 × 10−7 and 1.9 × 10−10 S cm−1, respectively. The latter material contained 77 wt% of silica. The original particulate nanostructure of the samples was preserved after carbonization. The carbon‐to‐nitrogen atomic ratio was 7.2 and 7.9; the nitrogen content in the carbonized polyaniline–poly(N‐vinylpyrrolidone) particles was 10.8 wt%. Thermogravimetric analysis in air revealed their stability to be up to 500 °C. This is comparable with commercial multi‐wall carbon nanotubes, which have similar areas of application. The nitrogen‐containing carbons are potentially useful as supports for catalysts and in applications where carbon of higher hydrophilicity would be of benefit. Copyright © 2010 Society of Chemical Industry

A comparative study of water dispersible polyaniline nanocomposites prepared by laccase‐catalyzed and chemical methods

AbstractA comparative study of chemical and enzymatic methods of aniline polymerization was carried out. Fungal laccase from Trametes hirsuta was used in the synthesis of polyaniline nanoparticles made with poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS). Template polymerization of aniline was carried out in aqueous buffer. It was shown that the laccase had high long‐term and operating stabilities under acidic condition favorable for synthesis of conducting polyaniline. UV‐vis, FTIR spectroscopy, and cyclic voltammetry analysis are used for the characterization of the polyelectrolyte complexes of polyaniline and PAMPS. The incorporation of the polymeric acid in polyaniline has been demonstrated by atomic force microscopy. The size and morphology of the nanoparticles of the polyaniline–PAMPS complexes depended on the method of the synthesis. A comparison of some physical and chemical properties of water dispersible conducting polyaniline–PAMPS was performed under production by enzymatic and chemical methods. It was found a difference in structures and some physicochemical properties of polyaniline colloids prepared by chemical and laccase‐catalyzed methods. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010