Self-doped Sulfonated Polyaniline Research Articles

Simplified in-situ tailoring of cross-linked self-doped sulfonated polyaniline (S-PANI) membranes for nanofiltration applications

Sulfonated polyaniline (S-PANI) membranes could have wide-ranging applications due to their electrical tunability, antifouling behaviour and chlorine resistance. However, S-PANI membranes below the ultrafiltration (UF) separation range have not been successfully established. This study presents a scalable approach to produce the first in-situ cross-linked S-PANI membranes at nanofiltration (NF) range. S-PANI membranes were produced by non-solvent induced phase separation (NIPS). The presence of sulfonic groups as polymer cross-linking anchors and controlling the coagulation bath's acidic strength resulted in instant stabilisation of the selective layer, which hindered the solvent/non-solvent exchange rate. This enabled the production of a tailored membrane morphology with a dense skin layer, suppressed macro-voids, reduced porosity, enhanced tensile strength, increased hydrophilicity and solvent stability. S-PANI membranes cast in 3 M HCl(aq) with MWCO≈680 g mol−1 (sucrose octa-acetate) showed a rejection of 99 % for PEG 1000 g mol−1 and 91–100 % for dye solution (MW range of 320–1017 g mol−1) compared to 34 % and 74–85 % rejection for a commercial fluoropolymer membrane (nominal MWCO 1000 g mol−1), respectively. The reported approach is simple and can be applied to design new classes of cross-linked solvent stable S-PANI NF membranes.

Comparative study on anticorrosion enhancement of carboxylated and sulfonated self-doped polyaniline on waterborne epoxy coating

Water-dispersed self-doped sulfonated polyaniline (SPANi) and self-doped carboxylated polyaniline (CPANi) were prepared by the copolymerization of aniline with m-aminobenzenesulfonic acid and m-aminobenzoic acid, respectively, and were identified by UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. The resultant SPANi and CPANi nanofibers were used as anticorrosion pigments for water epoxy coatings (EP). The corrosion resistance was compared using anticorrosive studies in 3.5 wt% NaCl solution using electrochemical impedance spectroscopy (EIS), polarization curves (Tafel), and a neutral salt spray (NSS) test. Polarization tests showed that the corrosion potential of SPANi/EP coating increased compared with CPANi/EP. EIS tests after 40-day immersion. This behavior further confirmed that the impedance modulus and coating resistance of SPANi/EP increased by three orders of magnitude compared with EP, which were two orders of magnitude higher than that of polyaniline (PANi)/EP and one order of magnitude higher than that of CPANi/EP.

Sulfonated Polyaniline as Zwitterionic and Conductive Interfaces for Anti-Biofouling on Open Electrode Surfaces in Electrodynamic Systems.

Electrodynamic systems for bioanalytical applications constantly suffer from biofouling due to electrical field-induced nonspecific bioadsorption on electrode surfaces. To minimize this issue, surface modification using anti-biofouling and conductive materials is necessary to not only protect the electrode surface from nonspecific bioadsorption but also maintain desired electrodynamic properties for electrode operation. In this study, we designed and prepared a conductive, zwitterionic, and self-doped sulfonated polyaniline (SPANI) coating on Au electrode surfaces for anti-biofouling applications. The zwitterionic coating was fabricated by electrochemical polymerization of aniline on the Au electrode surface functionalized with cysteamine (HS-CH2CH2-NH2) and then a post-polymerization treatment with fuming sulfuric acid. We found that the SPANI-coated electrodes exhibited an excellent anti-biofouling ability in dielectrophoresis (DEP) capturing-and-releasing processes, with a very low average residual mass rate of 1.44% for the SPANI-5s electrode, whereas electrodes modified with poly(ethylene glycol) (PEG) gave an average residual mass rate of 14.30%. Even under continuous operation for more than 1 h, the SPANI-5s electrode still showed stable anti-biofouling ability for an 11-cycle E. coli capturing-and-releasing DEP process, with the residual mass rate for all 11 cycles being kept at or below 2.18% to give an average residual mass rate of 1.62% with a standard deviation of 0.40%. This study demonstrates that electrodynamic systems with zwitterionic SPANI coated on open electrode surfaces can excellently function with decent conductance and anti-biofouling performance.

Fabrication of self-doped sulfonated polyaniline membranes with enhanced antifouling ability and improved solvent resistance

The fabrication of self-doped sulfonated polyaniline S-PANI membranes is reported here for the first time and addresses key challenges of PANI membranes including fouling, solvent stability issues and acid leaching. Sulfonation of the PANI-powder was confirmed by FTIR, UV-VIS and SEM-EDX characterisation. The membranes were prepared via phase inversion approach in water from a solution of 23% w/v S-PANI and were chemically cross-linked with three different organic cross-linkers: α,α′-Dichloro-p-xylene (DCX), glutaraldehyde (GA) and terephtaloyl chloride (TCL). PANI, S-PANI, S-PANI DCX, S-PANI TCL and S-PANI-GA were evaluated for their hydrophilicity, morphology, chemical properties and filtration performance showing that the chemically cross-linked S-PANI membranes have superior stability and reusability in DMF when tested in dead-end cell at 5 bar. Filtration experiments in water showed that S-PANI-GA has an increase in PEG rejection of 2.3 times and a MWCO of 1800 Da in contrast with PANI and SPANI, which showed a MWCO above 5000 Da. Fouling performance using BSA, showed a significant improvement of flux recovery for S-PANI and S-PANI GA, with the membranes regaining 87% and 83% of their original flux after one cleaning-fouling cycle. Conversely, PANI had a flux recovery of only 40%. The low irreversible fouling of the membranes, 13% for S-PANI and 17% for S-PANI GA, against 65% for PANI after 3 cycles is an encouraging result for the reduction of costly and high environmentally impact chemical cleaning in membrane processes. Overall, this study provides a simple method to produce low fouling and long-term solvent resistant membranes to enhance the widespread use of membrane technology in industrial processes.

Preparation of high-performance antifouling polyphenylsulfone ultrafiltration membrane by the addition of sulfonated polyaniline

In this work, blend ultrafiltration (UF) membranes were prepared on the basis of polyphenylsulfone (PPSU)/sulfonated polyaniline (SPANI). A synthesis method based on non-solvent induced phase separation (NIPS) with PPSU/SPANI dissolved in N-methyl-2-pyrrolidone (NMP) was proposed. The self-doped SPANI was prepared as zwitterionic polymer to improve the anti-fouling property of PPSU UF membrane. The morphological characteristics and structure of the membranes were observed under a field emission scanning electron microscope. Results revealed that the membranes exhibited a typical asymmetric structure with a dense top layer and a porous structure. The BSA adsorption of the modified membranes was weaker than that of the PPSU membrane. The water permeate fluxes of the prepared membranes were higher than those of the pure PPSU membrane. The PPSU/SPANI membrane showed highly improved water flux, which was almost 2 times higher than that of the PPSU membrane, whereas the rejection of prepared membrane was still maintained at a high level. The bovine serum albumin BSA rejection rate of the membranes decreased from 99% to 96%. The surface hydrophilicity of the static contact angle of the modified membranes increased. The X-ray photoelectron spectra and surface zeta potential of the membranes were also examined. The water flux recovery ratio, total fouling ratio, reversible fouling ratio, and irreversible fouling ratio also enhanced the antifouling property of the modified membranes. The proposed method provides a simple and convenient approach to prepare antifouling UF membranes.

Corrosion protection performance of waterborne epoxy coatings containing self-doped polyaniline nanofiber

Self-doped sulfonated polyaniline (SPANi) nanofiber was synthesized by the copolymerization of 2-aminobenzenesulfonic acid (ASA) and aniline via a rapid mixing polymerization approach. The chemical structure of SPANi was investigated by the Fourier-transform infrared (FT-IR), Raman, X-ray photoelectron spectroscopy (XPS), UV–vis spectra and X-ray diffraction (XRD) pattern. The as-prepared SPANi nanofibers had 45nm average diameter and length up to 750nm as measured by scanning electron microscope (SEM) and transmission electron microscope (TEM). The self-doped SPANi nanofiber possessed excellent aqueous solubility, good conductivity (0.11S/cm) and reversible redox activity, making it suitable as a corrosion inhibitor for waterborne coatings. The prepared SPANi/waterborne epoxy composite coatings exhibited remarkably improved corrosion protection compared with pure waterborne epoxy coating as proved by the polarization curves and electrochemical impedance spectroscopy (EIS). The passivation effect of SPANi nanofiber and the corrosion products beneath the epoxy coatings immersed in 3.5% NaCl solution as a function of time were also investigated in this study.

Efficient Preparation of Super Antifouling PVDF Ultrafiltration Membrane with One Step Fabricated Zwitterionic Surface.

On the basis of the excellent fouling resistance of zwitterionic materials, the super antifouling polyvinylidene fluoride (PVDF) membrane was efficiently prepared though one-step sulfonation of PVDF and polyaniline blend membrane in situ. The self-doped sulfonated polyaniline (SPANI) was generated as a novel zwitterionic polymer to improve the antifouling property of PVDF ultrafiltration membrane used in sewage treatment. Surface attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, surface zeta potential, and water contact angle demonstrated the successful fabrication of zwitterionic interface by convenient sulfonation modification. The static adsorption fouling test showed the quantified adsorption mass of bovine serum albumin (BSA) pollutant on the PVDF/SPANI membrane surface decreases to 3(±2) μg/cm(2), and the water flux recovery ratio (FRR) values were no less than 95% for the three model pollutants of BSA, sodium alginate (SA), and humic acid (HA), which were corresponding hydrophobic, hydrophilic, and natural pollutants in sewage, respectively. This Research Article demonstrated the antifouling advantages of zwitterionic SPANI and aimed to provide a simple method for the large scale preparation of zwitterionic antifouling ultrafiltration membranes.

Self-doped polyaniline-based interdigitated electrodes for electrical stimulation of osteoblast cell lines

We report a facile method of synthesis and fabrication of self-doped sulfonated polyaniline (SPAN)-based interdigitated electrodes (IDEs) for cell stimulation. In this method, a layer-by-layer of SPAN copolymers was deposited by in situ polymerization on a micropattern printed polyethylene teraphthalate (PET) film. Bone marrow stromal cells (BMSCs) and pre-osteoblast cells (MC3T3-E1) were utilizing for the cell compatibility and proliferation studies. Increased degree of sulfonation was found to increase the SPAN conductivity, which in turn improved the cell attachment and cell growth. The in vitro osteogenesis of the BMSCs or the MC3T3-E1 cells grown on the SPAN based IDEs under the electrical stimulation was investigated by utilizing an alkaline phosphatase (ALP) activity assay. The Von Kossa staining of the cells revealed significantly increased mineralization by both the cells compared to their respective controls (without electrical stimulation). The high electrical conductivity and stability of the SPAN in a broad pH range of physiological culture medium in addition to the excellent cytocompatibility make the SPAN based IDEs as potential scaffold materials for in vitro cell culture and tissue engineering applications.

Sulfonated Polyaniline-Based Organic Electrodes for Controlled Electrical Stimulation of Human Osteosarcoma Cells

Electrically conducting polymers (CPs) were found to stimulate various cell types such as neurons, osteoblasts, and fibroblasts in both in vitro and in vivo studies. However, to our knowledge, no studies have been reported on the utility of CPs in stimulation of cancer or tumor cells in the literature. Here we report a facile fabrication method of self-doped sulfonated polyaniline (SPAN)-based interdigitated electrodes (IDEs) for controlled electrical stimulation of human osteosarcoma (HOS) cells. Increased degree of sulfonation was found to increase the SPAN conductivity, which in turn improved the cell attachment and cell growth without electrical stimulation. However, an enhanced cell growth was observed under controlled electrical (AC) stimulation at low applied voltage and frequency (≤800 mV and ≤1 kHz). The cell growth reached a maximum threshold at an applied voltage or frequency and beyond which pronounced cell death was observed. We believe that these organic electrodes may find utility in electrical stimulation of cancer or tumor cells for therapy and research and may also provide an alternative to the conventional metal-based electrodes.

Fabrication and photovoltaic properties of self-assembled sulfonated polyaniline/TiO 2 nanocomposite ultrathin films

Two kinds of TiO 2/sulfonated polyaniline (SPAn) nanocomposite ultrathin films were fabricated by layer-by-layer (LBL) self-assembly technique on various solid surfaces. One was fabricated with self-doped sulfonated polyaniline (SD-SPAn) and TiO 2 sol, and another was with externally (HCl)-doped sulfonated polyaniline (ED-SPAn) and TiCl 4. The linear growth of both the LBL films was proved by UV–vis spectroscopy. The ordered multilayer films were subsequently characterized by atomic force microscopy, cyclic voltammetry, and photoelectrochemical measurement. Their structure, electrochemical and photoelectrochemical properties were comparatively investigated. The morphology of ED-SPAn/TiO 2 LBL films is evener and smoother than that of SD-SPAn/TiO 2 LBL films. Two kinds of LBL films have different electrochemical behaviours, and ED-SPAn/TiO 2 LBL films show a stabler but slower photocurrent response than SD-SPAn/TiO 2 LBL films.

In situ Raman spectroelectrochemical study of self-doped polyaniline degradation kinetics

The kinetics of electrochemical degradation for a self-doped sulfonated polyaniline derivative (a copolymer of aniline and m-aminobenzenesulfonic acid) has been studied with in situ Raman spectroscopy. It has been shown that the degradation proceeds faster in more acidic solutions. From the data obtained, first-order degradation rate constants have been calculated. Within the solution pH range of 0.5–9.0, first-order rate constants thus obtained vary, respectively, between (6.6 ± 0.8) × 10 −4 s −1 and (0.8 ± 0.1) × 10 −4 s −1 for electrode potential of 0.8 V vs. Ag/AgCl. A linear correlation between the degradation rate constant and solution pH has been found: log k = log k 0 + a · pH, where k represents rate constant at any pH (expressed in s −1), k 0 is the rate constant for pH 0, log k 0 = −3.09, and a = −0.11 is the slope of (log k, pH) dependence.

Voltammetric study of the redox processes of self-doped sulfonated polyaniline

Electrochemical redox properties of self-doped copolymer of aniline and m-aminobenzenesulfonic acid (metanilic acid), electrodeposited on platinum electrode, were studied in different electrolytes. Two reversible redox processes with the midpoint potentials of 0.21–0.25, and 0.41 V vs. Ag/AgCl were found for copolymer films of different redox capacity in 0.1 M sulfuric acid solution. Copolymer films are redox active in nearly pH–neutral solutions, however, their activity depend greatly on the cation present in electrolyte. Well expressed redox behavior has been observed in ammonium sulfate, chloride, nitrate, and phosphate buffer pH 7 solutions, whereas suppressed redox properties were found in the corresponding sodium salt solutions. This difference has been discussed in terms of cation exchange between the copolymer film and solution during redox cycling. In an acidic solution, the copolymer shows electrocatalytic behavior for the hydroquinone/benzoquinone redox couple, whereas in neutral solutions no electrocatalysis for this couple, as well as inhibition of redox processes for Fe 3+/2+ and Fe(CN) 6 3−/4− couples was observed.

Electrochemical synthesis of self-doped polyaniline in fluorosulfonic acid/acetonitrile solution

Electrochemical formation of self-doped sulfonated polyaniline (SPAN) was carried out in acetonitrile-containing anhydrous fluorosulfonic acid (FSO 3H). Fluorosulfonic acid was used as both sulfonation reagent for aniline and also as supporting electrolyte. The degree of sulfonation of the polymer was controlled by varying FSO 3H and aniline concentrations while the film is being deposited. Different dry conductivity values for the polymer (1.24–14.6 S/cm) were measured depending on the degree of sulfonation of polyaniline. Polychromic behavior of SPAN (transparent yellow–green–dark blue) was observed when the cyclic voltammograms were taken between −0.30 and +1.90 V (vs. Ag/AgCl, saturated) during the growth of polyaniline film. The polymers having different degrees of sulfonation were found to be soluble in basic aqueous solution, dimethyl sulfoxide (DMSO) and N-methylpyrrolidone (NMP). SPAN was characterized by elemental analysis, FT-IR spectroscopy, UV–visible spectroscopy and cyclic voltammetry.

Corrosion protection of aluminum and aluminum alloys by polyanilines: A potentiodynamic and photoelectron spectroscopy study

AbstractCorrosion protection capabilities of polyaniline in the emeraldine base form and self-doped sulfonated polyaniline form have been studied for aluminum and Al 3003 and Al 2024-T3 alloys. The polyaniline is applied as a coating on the aluminum coupons which were exposed to a variety of corrosive environments, including 0.1 M NaCl. The oxide layers that formed were studied by X-ray photoelectron spectroscopy depth profiling using argon sputtering. Potentiodynamic polarization studies were used to determine changes in corrosion current and corrosion potential as well as pitting potential. For Al and Al 3003 there were modest indications of potential corrosion protection capability of polyanilines. The coatings of emeraldine base (EB) and sulfonated polyaniline (SPAN) on Al 2024-T3 were effective at reducing the corrosion rate when these coated coupons were exposed to 0.1 M NaCl environment. The XPS study suggests a reduction in the copper concentration at the surface of the coated coupons. It is suggested that the EB and sulfonated polyaniline coatings facilitate the extraction of copper from the surface of the Al 2024-T3 thereby reducing the galvanic couple between aluminum and copper that usually leads to accelerated corrosion for the Al 2024-T3 alloys.

Pressure—temperature-induced conductivity in polyaniline base and salts

The conductivities of polyaniline (and poly(2-methoxyaniline), poly(2-methylaniline)) and of the sulfonated derivative have been studied as a function of pressure (0 to 30 kbar) and of temperature (20 to 100–400 °C). Conductivity measurements were made with the aid of impedance spectroscopy in a piston—cylinder high-pressure cell. The conductivity of emeraldine chloride is quite stable up to 10 kbar and then increases continuously up to a factor 50 (1 to 60 S cm −1 at 100 °C, 25 kbar). Similar behaviour is observed for the ortho-substituted derivatives (poly(2-methylaniline) and poly(2-methoxyaniline)) as well as for the self-doped sulfonated polyaniline. The conductivity increases regularly with temperature and then drops irreversibly: highest values are observed at 90, 70 and 60 °C for the self-doped material and the chlorides, poly(2-methoxyaniline chloride) and poly(2-methylaniline chloride), respectively. A strong increasing in conductivity is observed versus temperature and pressure, up to 10 −4 S cm −1, at 300 °C under 20 kbar for the emeraldine base. The nature of the charge carriers (electrons or protons) is discussed.

Electronic control of pH at sulfonated polyaniline electrodes

Electrochemical modulation of self-doped sulfonated polyaniline is demonstrated to provide electronic control of pH and enzyme activity in the vicinity of the electrodes.