Polystyrene Sulphonate Research Articles

Incorporating Biodopants into PEDOT Conducting Polymers: Impact of Biodopant on polymer properties and biocompatibility

ABSTRACTPoly(3,4-ethylenedioxythiophene) (PEDOT) was polymerized with the biological dopants dextran sulphate and chondroitin sulphate. Polymer physical and mechanical properties were investigated using quartz crystal microgravimetry with dissipation monitoring and atomic force microscopy, revealing polymer shear modulus and interfacial roughness to be significantly altered as a function of the dopant species. The adsorption of fibronectin, an important extracellular protein that is critical for a range of cellular functions and processes, was investigated using QCM-D, revealing protein adsorption to be increased on the DS doped PEDOT film relative to the CS doped film. PEDOT films have traditionally been doped with synthetic counterions such as polystyrene sulphonate (PSS), however the incorporation of biological molecules as the counterion, which has been shown to improve polymer biofunctionality, has received far less attention. In particular, there has been little detailed study on the impact of incorporating polyelectrolyte biomolecules into the PEDOT polymer matrix on fundamental polymer properties which are critical for biomedical applications. This investigation provides a detailed characterization of the interfacial and mechanical properties of biologically doped PEDOT films, as well as the efficacy of the composite films to bind and retain extracellular proteins of the type that are critical to the biocompatibility of the polymeric material.

Synthesis of polyaniline-based inks, doping thereof and test device printing towards electronic applications

Polyaniline (PANI) was synthesised by oxidation polymerization starting from aniline dimer, thus avoiding the use of a toxic/mutagenic substance such as aniline. In order to work in an aqueous phase, polystyrene sulphonate (PSS) was used as an emulsioning/doping agent. The fine tuning of oxidant quantity allowed the production of PANI in the mixed leucoemeraldine/emeraldine oxidation states. PANI/PSS was solubilised in dimethylsulphoxide and used as ink for the fabrication of inkjet printed tracks, which showed an interesting negative capacitance effect that can be attributed to the presence of different oxidation states and the partial doping obtained by the use of PSS. Negative capacitance devices are extremely attractive in high frequency applications where positive parasitic capacitances have to be compensated.

Polyanion-induced circular dichroism of Thioflavin T

Thioflavin T (ThT) is amyloid specific fluorescence dye possessing the properties of molecular rotor. We have shown that Thioflavin T forms complexes with non-peptide polyanions heparin, polyadenylate and polystyrene sulphonate by means of absorption spectroscopy. In the presence of chiral polyanions - heparin and polyadenylate - induced optical activity of ThT occurs whereas interaction with achiral polystyrene sulphonate (PSS) does not lead to production of induced circular dichroism signal. The positively charged ThT forms centre for ordered binding of chiral polyanion. Similarly, complexation of structurally different chromophore 9-aminoacridine with polyanions has led to induction of optical activity only in the presence of chiral ones. We suggest that, primarily, the optical activity of environment plays important role in inducing optical activity of achiral compounds.

Studies of Electrolytic Conductivity of Some Polyelectrolyte Solutions: Importance of the Dielectric Friction Effect at High Dilution

We present a general description of conductivity behavior of highly charged strong polyelectrolytes in dilute aqueous solutions taking into account the translational dielectric friction on the moving polyions modeled as chains of charged spheres successively bounded and surrounded by solvent molecules. A general formal limiting expression of the equivalent conductivity of these polyelectrolytes is presented in order to distinguish between two concentration regimes and to evaluate the relative interdependence between the ionic condensation effect and the dielectric friction effect, in the range of very dilute solutions for which the stretched conformation is favored. This approach is illustrated by the limiting behaviors of three polyelectrolytes (sodium heparinate, sodium chondroitin sulfate, and sodium polystyrene sulphonate) characterized by different chain lengths and by different discontinuous charge distributions.

Silver nanowire-polymer composite electrode for high performance solution-processed thin-film transistors

Silver nanowires (AgNWs)/poly-(3,4-ethylenedioxythiophene/polystyrene sulphonate) (PEDOT:PSS) composite films as conductive electrode for OTFTs were prepared, and their optical and electrical properties were investigated. The conductive composite films used in this study afforded low sheet resistance of <140Ω/sq and transmittance as high as 70% in the visible region. For the composite film with 0.1wt.% of AgNWs, contact resistance as low as 2.7×104Ωcm was obtained, as examined by Transfer length model (TLM) analysis, and work function of the corresponding film was 5.0eV. Furthermore, the composite films were employed as source and drain electrodes for top-gate/bottom-contact organic thin-film transistors (OTFTs) based on solution-processed 5,11-bistriethylsilylethynyl anthradithiophene (TES-ADT) as organic semiconductor, and the resulting device showed high electrical performance with carrier mobility as high as 0.21cm2/Vs.

Corrosion protection of cold-rolled steel with alkyd paint coatings composited with submicron-structure types polypyrrole-modified nano-size alumina and carbon nanotubes

Abstract This paper is focused on studying corrosion protection of cold-rolled steel with alkyd paint coatings comprising nano-size alumina and either polystyrene-sulphonate (PSS) modified or sulphonated multi-walled carbon nanotube (MWCNT) supported polypyrrole (PPy). Single layer coatings (in thickness of 40 ± 5 μm) comprising PPy deposited alumina and PSS modified MWCNT supported PPy afforded viable protection during the 1 M sodium chloride test. The coatings containing PSS modified and weakly sulphonated MWCNTs (at volume fractions of 9.9 × 10−4 and 2.5 × 10−4) with PPy volume fractions of 3.5 × 10−3 and 2.5 × 10−3 provided effective corrosion prevention during the 1 M sodium chloride and hydrochloric acid solution tests. While inhibitor particles were characterised by infrared spectroscopy, corrosion products formed at the paint–steel interface were studied by X-ray photoelectron spectroscopy. Apart from the electron microscopy observations, rheology study of three-dimensional structure of the inhibitor particles was performed in dispersions at similar compositions to those used for the paint formulations. Thus, protection mechanism relating to both types of immersion tests is discussed in terms of properties of the inhibitor particles and their microstructure in the coatings.

Poly(3,4-ethylenedioxythiophene) based enzyme-electrode configuration for enhanced direct electron transfer type biocatalysis of oxygen reduction

An O2-consuming cathode for biofuel cell applications consisting of Trametes hirsuta laccase (ThL) immobilized in an electropolymerized fine-tuned poly(3,4-ethylenedioxythiophene) (PEDOT) bilayer structure as the catalyst was studied. A NO3−-doped PEDOT layer with a relatively porous structure was used as the immobilization matrix on which the enzyme was added by solution casting. A capping layer of polystyrene sulphonate, PSS−-doped PEDOT was then electrodeposited on top of the first PEDOT layer in order to entrap the ThL between the layers. The PEDOT-NO3−/ThL/PEDOT-PSS− enzyme electrode is reported to be able to promote direct electron transfer (DET) between ThL and the current collector and it catalyzes the reduction of O2 into water. The applicability of the PEDOT-NO3−/ThL/PEDOT-PSS− enzyme electrode structure on ITO glass with a geometrical surface area of 1cm2 as the electrode material was studied. The influence of different enzyme electrode fabrication parameters, such as the dopant ion used during electropolymerization, different combinations of PEDOT films, the thickness of both PEDOT layers and ThL loading on the enzyme electrode performance were investigated by chronoamperometric and cyclic voltammetric measurements. The optimum working pH for the enzyme electrode was found to be in the pH range 3.0–3.5. No enhanced cell performance was recorded when 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) was used as mediator compared to DET in the PEDOT bilayer structure.

A comparative assessment of surface microstructure and electrical conductivity dependence on co-solvent addition in spin coated and inkjet printed poly(3,4-ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS)

This study focuses on the fabrication of poly(3,4-ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS) thin films by inkjet printing and investigates the developed surface morphology and electrical conductivity of the printed films as a function of the concentration of dimethyl sulfoxide (DMSO), added as conduction enhancing co-solvent, and Surfynol, added as a surfactant. The printed films are compared with PEDOT:PSS films fabricated by the traditional spin coating technique. Measurements of the surface tension justify including surfactant as a processing additive, where addition of 1% Surfynol results in substantial decrease of the surface tension of the PEDOT:PSS solution, whilst it also increases film surface roughness by an order of magnitude for both fabrication methods. The addition of 5wt% DMSO is shown to result in a 103 decrease in sheet resistance for both spin coated and inkjet printed films with both processing routes demonstrating decrease in surface roughness and coarsening of PEDOT grains as a function of the co-solvent concentration, whilst X-ray photon spectroscopy showed an increase in the surface PEDOT to PSS ratio from 0.4 to 0.5. Inkjet printed films have lower sheet resistance than the corresponding spin coated films, whilst atomic force microscopy reveals a coarser surface morphology for the inkjet printed films. The findings in this work point out at the decrease of sheet resistance due to coarsening of PEDOT grains which is linked to a decrease of surface roughness for small RMS values associated with the PEDOT grains. However, the higher surface roughness generated when Surfynol surfactant was added was not detrimental to the film’s in-plane conductivity due to the fact that these higher roughness values were unrelated to the PEDOT grains.

Electrophoretic separation of neurotransmitters on a polystyrene nano-sphere∕polystyrene sulphonate coated poly(dimethylsiloxane) microchannel.

In this paper, a poly(dimethylsiloxane) microchip with amperometric detector was developed for the electrophoretic separation and determination of neurotransmitters. For increasing the separation efficiency, the microchannel is modified by polystyrene sulphonate∕polystyrene nano-sphere self-assembly coating. A stable electro-osmotic flow (EOF) and higher separation efficiency are obtained in proposed modified microchannel. Under optimized conditions, dopamine, epinephrine, catechol, and serotonin are acceptably baseline separated in this 3.5 cm length separation channel with the theoretical plate number from 4.6 × 10(4) to 2.1 × 10(5) per meter and resolution from 1.29 to 12.5. The practicability of proposed microchip is validated by the recovery test with cerebrospinal fluid as real sample which resulted from 91.7% to 106.5%.

Titania shells with single crystallites layer thickness and the photocatalysis properties

TiO2 shells comprised of single-layer nanocrystallites were synthesised using sulphonated polystyrene (SPS) nanospheres as hard templates. The assembling of titania gel-based particles during the hydrolysation process caused the formation of SPS–titania gel core–shell spheres, the dissolution of SPS and the condensation process by calcination resulting in single-layer crystallites-connected TiO2 shells with a rough surface. The prepared TiO2 shells showed considerable photocatalytic activity on the degradation of Rhodamine B.

Stability of poly(3,4‐ethylene dioxythiophene) materials intended for implants

This study presents experiments designed to study the stability of the conducting polymer poly(3,4-ethylene dioxythiophene) (PEDOT), under simulated physiological conditions using phosphate-buffered saline (PBS) and hydrogen peroxide (H(2)O(2)) (0.01 M) at 37 degrees C over a 5- to 6-week period. Voltage pulsing in PBS was used as an additional test environment. The influence of switching the counter ion used in electropolymerization from polystyrene sulphonate (PSS) to heparin was investigated. Absorbance spectroscopy and cyclic voltammetry were used to evaluate the material properties. Most of the samples in H(2)O(2) lost both electroactivity and optical absorbance within the study period, but PEDOT:PSS was found slightly more stable than PEDOT:heparin. Polymers were relatively stable in PBS throughout the study period, with around 80% of electroactivity remaining after 5 weeks, disregarding delamination, which was a significant problem especially for polymer on indium tin oxide substrates. Voltage pulsing in PBS did not increase degradation. The counter ion influenced the time course of degradation in oxidizing agents.

Preparation and characterization of activated carbon spheres from polystyrene sulphonate beads by steam and carbon dioxide activation

AbstractThe polymeric precursor polystyrene sulphonate beads were used to produce activated carbon spheres (ACSs). ACSs were prepared by carbonization of polymeric precursor at 800°C followed by activation of resultant char with steam and carbon dioxide activation processes. The resulting ACSs were characterized for N2 adsorption, Raman spectrometry, and scanning electron microscope (SEM). The adsorption properties such as, BET surface area (SBET), pore volume (Vpore), and micropore volume (Vmicro) of ACSs produced at different gasification time and temperature with steam and carbon dioxide activation were investigated in this study. It is found that porosity of ACSs produced from steam and carbon dioxide activation increases with increasing activation time. The results exhibited that ACSs produced from above carbon dioxide activation have shown high SBET and Vpore 1266 m2/g and 1.13 cm3/g respectively compared to ACSs from steam activation SBET 949 m2/g and Vpore 0.98 cm3/g, respectively. SEM study revealed that ACSs produced from carbon dioxide activation have exhibited a smooth surface and better microstructure as compared to ACSs from steam activation process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Entrapment of live microbial cells in electropolymerized polyaniline and their use as urea biosensor

The lyophilized biomass of bacterium Brevibacterium ammoniagenes was immobilized in polystyrene sulphonate–polyaniline (PSS–PANI) conducting polymer on a Pt twin wire electrode by potentiostatic electropolymerization. The bacterial cells retained their viability as well as urease activity under entrapped state, as confirmed with bacterial live–dead fluorescent assay and enzymatic assays. The entrapped cells were visualized using scanning electron microscope. The immobilized cells were used as a source of unpurified urease to develop a conductometric urea biosensor. The catalytic action of urease in the sensor released ammonia, thereby causing an increase in the pH of the microenvironment. The pH dependant change in the resistivity of the polymer was used as the basis of sensing mechanism. The sensor response was linear over a range of 0–75mM urea with a sensitivity of 0.125mM−1. The sensor could be reused for 12–15 independent measurements and was quite stable in dry as well as buffered storage condition at 4°C for at least 7 days.

Composite biomolecule/PEDOT materials for neural electrodes

Electrodes intended for neural communication must be designed to meet both the electrochemical and biological requirements essential for long term functionality. Metallic electrode materials have been found inadequate to meet these requirements and therefore conducting polymers for neural electrodes have emerged as a field of interest. One clear advantage with polymer electrodes is the possibility to tailor the material to have optimal biomechanical and chemical properties for certain applications. To identify and evaluate new materials for neural communication electrodes, three charged biomolecules, fibrinogen, hyaluronic acid (HA), and heparin are used as counterions in the electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). The resulting material is evaluated electrochemically and the amount of exposed biomolecule on the surface is quantified. PEDOT:biomolecule surfaces are also studied with static contact angle measurements as well as scanning electron microscopy and compared to surfaces of PEDOT electrochemically deposited with surfactant counterion polystyrene sulphonate (PSS). Electrochemical measurements show that PEDOT:heparin and PEDOT:HA, both have the electrochemical properties required for neural electrodes, and PEDOT:heparin also compares well to PEDOT:PSS. PEDOT:fibrinogen is found less suitable as neural electrode material.

Corrosion properties of 316L stainless steel coated with polyelectrolyte multilayers of varying anionic acidity

Polyelectrolytes have been proposed as promising systems for the potection of stainless steels and for biomedical and drug release applications. Multilayer nanofilms with varying anion acidity were deposited on AISI316L stainless steel. The cationic polyelectrolyte was polyallylamine hydrochloride (PAH) whereas the anionic polyelectrolytes with increasing acidity were polyacrylic acid (PAA), polystyrene sulphonate-co-maleic acid and polystyrene sulphonate (PSS). Potentiodynamic polarisation showed an increase in corrosion potential Ecorr upon coating with multilayer nanofilms and a corresponding decrease in corrosion current. Transient currents were observed upon application of PSS due to its high acidic strength although it showed better pit recovery characteristics as shown in cyclic polarisation experiments. Constant potential experiments at 700 mV v. Ag/AgCl for 12 h showed a suppressed current by 50% for the PAH/PSS coated steel compared to the uncoated specimen. The SEM images showed the existence of agglomerates, uncovered areas and corrosion products underneath channels on the coating.

Effect of Solute‐Polymer Interactions on Sorption and Diffusion in Polyacrylamide Gels

Solute‐polymer interactions can exert a large effect on selective sorption and permeation in polyacrylamide (PAAm) gels. In order to investigate this effect, three probe polyelectrolytes, sodium polystyrene sulphonate (PSS), polyvinylpyrrolidone (PVP), and sulfonated polyaniline (SPANI), were chosen as probe species in sorption, release, and permeation experiments in PAAm gels. For PAAm gels with trapped SPANI, FTIR spectroscopy has confirmed that there exists hydrogen‐bonding between SPANI and PAAm. In addition, rigid‐chain SPANI has an intense tendency to aggregate; it is likely that the effective chains of the PAAm matrices are enwrapped in these aggregates. Hydrogen‐bonding and aggregation resulted in that the release kinetics of SPANI from PAAm gels exhibited a remarkable “lag time”, as long as 100 h (lag period means that in the initial period there is no detectable SPANI released from PAAm gels.), the releasing rate of SPANI was very slow, and the selective sorption of SPANI in PAAm gels was extremely high. On the other hand, the release and permeation of PVP and PSS through PAAm gels were much faster than SPANI, and the selective sorption were close to unity. From these facts it could be deduced that there is no or only weak interaction between PAAm and PSS (or PVP). Adding of concentrated support electrolyte resulted in decrease of the release rate and a two‐magnitude decrease of the calculated diffusion coefficients of PSS; the effect of support electrolyte on release and permeation of PSS was partly attributed to the electrostatic interaction.

A dual chamber model of female cervical mucosa for the study of HIV transmission and for the evaluation of candidate HIV microbicides

A dual chamber system was established to model heterosexual HIV transmission. Cell-associated, but not cell-free HIV, added to a confluent layer of cervical epithelial cells in the apical chamber, reproducibly infected monocyte-derived dendritic cells (MO-DC) and CD4 + T cells in the basal compartment. Only minimal epithelial transmigration of HIV-infected mononuclear cells (HIV-PBMCs) was observed. Most evidence points to transepithelial migration of virus, released from HIV-PBMCs after their activation by epithelial cells. We used this model for evaluation of the therapeutic index of various potentially preventive antiviral compounds, including non-nucleoside reverse transcriptase inhibitors (NNRTIs, including UC781 and various diaryltriazines and diarylpyrimidines), poly-anionic entry inhibitors (including PRO2000, cellulose sulphate, dextrane sulphate 5000 and polystyrene sulphonate) and the fusion inhibitor T-20. The epithelium was pre-treated with compound and incubated with HIV-PBMCs for 24 h. Afterwards the apical chamber was removed and MO-DC/CD4 + T cell co-cultures were further cultured without compound. NNRTIs, including a TMC120 gel, blocked infection of the sub-epithelial targets at sub-micromolar concentrations. Polyanionic entry inhibitors (up to 100 μg/ml) and T-20 (up to 449 μg/ml) failed to inhibit transmission. Moreover, whereas the NNRTIs used interfered with epithelial integrity with cervical epithelium only at very high concentrations, the evaluated entry inhibitors showed toxicity at concentrations that did not prevent infection.

The polymer and salt induced aggregation of silica particles

Dynamic light scattering (DLS) was used to map the stability of an aqueous silica colloid in the presence of differing concentrations of sodium polystyrene sulphonate (PSS) and sodium chloride (NaCl). Additionally, values of PSS size with salt and PSS osmotic pressure were measured as a function of PSS concentration. Six theoretical maps based on DLVO and simple depletion theory were then constructed as a comparison to the experimental map using the measured values as well as two theoretical values of PSS size and osmotic pressure. It was found that DLVO overestimates the effect of salt screening and of the various comparisons those calculated using size and osmotic pressure derived from a PSS chain with 1 charge between 5 monomers showed the greatest similarities to the experimental work.

Near-infrared emission of Nd-PSS films

We report a study of a new chemical synthetic route of polystyrene sulphonate (PSS) films doped with neodymium ion (Nd+3) from a neodymium nitrate solution. The UV-Vis-NIR spectrum presents an intense characteristic electronic transition at 800 nm and the infrared spectrum presents low definition bands as a result of Nd3+ coordination with PSS molecule. Additionally, the spectrum of Nd-PSS film presents the same line shape profile of Nd3+ salt in aqueous solution. Selective luminescence spectroscopy measures shows that the incorporation of neodymium ion introduces a red shift bands and a better line shape definition in UV luminescence compared to PSS film, decreasing the interaction between PSS aromatic groups. The near-infrared emission was observed in the large spectrum region from 600 to 800 nm; it is associated with the Nd3+ complex of PSS monomer.

Micro-cylinder biosensors for phenol and catechol based on layer-by-layer immobilization of tyrosinase on latex particles: Theory and experiment

Abstract Microelectrode sensors for phenol and catechol are described, based on the sequential immobilization of polystyrene sulphonate, polyallylamine, tyrosinase and polyallylamine again, onto micrometer scale latex spheres, followed by the adsorption of the spheres onto electrochemically pretreated carbon fibres. The steady state responses of the fibres are analyzed in terms of a cylindrical diffusion – kinetic model. It is deduced that the adsorbed latex particles provide a relatively open film structure, resulting in a diffusion coefficient only one order of magnitude lower than the solution value, and that at minimum 2–3% of the immobilized enzyme is catalytically active. The optimised sensors exhibit linear ranges to phenol and catechol of 7–56.5 μM and 2–19.7 μM respectively, with sensitivities of 0.15 A M−1 cm−2 and 1.72 A M−1 cm−2 respectively. The limiting factor to sensor stability is desorption of latex from the fibres.