Versatile poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) films on polydimethylsiloxane substrates having random micro ridges: Study of resistive behaviors of a polymer–polymer laminate

Conductive polymers such as poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) or PEDOT:PSS has become increasingly important in present day organic electronics. PEDOT:PSS being a polymer is more durable than metals used in electronics and thus offers greater mechanical flexibility during operation. This article presents results regarding resistive behaviors of blade coated PEDOT:PSS films on polydimethylsiloxane (PDMS) substrate having random micro ridges as a function of axial strain and different temperatures. The average resistance of the blade coated PEDOT:PSS films were found to increase by 1.4 times between 35 and 45% axial strain. The resistances of the films were found to change within the temperature range of 25–230°C without any thermal morphological degradations and the polymer–polymer laminate also showed linear thermal actuation behavior. These results suggest that the blade coated PEDOT:PSS films on PDMS substrates with random micro ridges can be potentially useful in versatile applications like stretchable conductors, thermal actuators, thermoelectric generators, and as heating surfaces. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41235.     

Electroconductive paper prepared by coating with blends of poly(3,4‐ethylenedioxythiophene)/poly(4‐styrenesulfonate) and organic solvents

Electroconductive papers were produced by coating commercial base papers with blends of poly(3,4‐ethylenedioxythiophene)/poly(4‐styrenesulfonate) (PEDOT:PSS) and organic solvents. The bulk conductivities of the coated papers were measured using a four‐probe technique. One‐sided and two‐sided coating gave comparable conductivity levels. The presence of sorbitol and isopropanol in the PEDOT:PSS blends did not enhance the bulk conductivity of the coated paper, and with increasing concentrations of these solvents, the conductivity decreased due to dilution of the conducting component. Samples coated with PEDOT:PSS blends containing N‐methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO) exhibited a higher conductivity than those coated with pure PEDOT:PSS because of their plasticizing effect and conformational changes of PEDOT molecules indicated by the red shift and disappearance of the shoulder peak at about 1442 cm^?1 in the Raman spectra of the coated samples. EDS imaging showed that PEDOT:PSS is distributed throughout the thickness direction of the paper. Contact angle measurements were made to monitor the hydrophilicity of the paper surface and total sulfur analysis was used to determine the amount of PEDOT:PSS deposited onto the paper. The tensile strength of all the paper samples increased slightly after treatment. Thus, it is demonstrated that enhanced bulk conductivity in the order of 10^?3 S/cm can be achieved by using organic conductive materials and surface treatment techniques. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

High cycling stability and well printability poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate)/multi‐walled carbon nanotube nanocomposites via in situ polymerization applied on electrochromic display

A high cycling stability material and an additive manufacturing method are reported for the fabrication of solid electrochromic devices. The poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate)/multi‐walled carbon nanotube (PEDOT:PSS/MWCNT) nanocomposites were synthesized via in situ polymerization. A carboxymethyl cellulose gel was used as the ink vehicle for screen printing. The electrochromic (EC) performance of films patterned by screen printing was also examined. The results of characterization indicate that strong interfacial interactions occurred between PEDOT:PSS and the MWCNTs and the MWCNTs formed a network in these conducting polymers film, so the composite was more conductive than pure PEDOT:PSS. Devices containing PEDOT:PSS/MWCNTs were more stable after 1000 cycles, exhibited higher rate of ion exchange and faster increases in current. The composite containing 0.3 wt % MWCNTs also had a 23% higher color contrast (ΔE*) than pure PEDOT:PSS at 2.5 V applied voltages. The EC inks with well printability not only can be used to print large area films, but also can print fine lines and pixel‐type dots in displays. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45943.     

The influence of thermal cycling and compressive force on the resistance of poly(3,4‐ethylenedioxythiophene)/poly(4‐styrenesulfonic acid)‐coated surfaces

There is an increasing interest in the use of conducting polymers for a wide variety of applications. This includes the study and development of alternative contact‐connector materials. The main aim is to achieve overall improvements in performance as well as cost effectiveness. Currently, extrinsic conducting polymers (ECPs) are employed as conductive coats or adhesives at contact interfaces. However, frictional abrasion within the metal‐doped polymer (ECP) causes instability in the resistance. It is important to overcome this fretting effect, especially in automotive applications; hence, the possibilities of employing intrinsically conducting polymers (ICPs) are explored. Flat contact film coatings have been fabricated in‐house using poly(3,4‐ethylenedioxythiopene)/poly(4‐styrenesulfonic acid) (PEDOT/PSS) with dimethylformamide as the secondary solvent. Resistance is measured using the four‐wire method. The conductivities of the PEDOT/PSS‐coated contacts are found to be in the order of 10^?2 S cm^?1. The change of resistance under varying compression forces has been found to be repeatable. The thermal effects on these contacts are also studied and the results are depicted as exponential negative temperature coefficients of resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2445–2452, 2006     

Preparation and performance of a transparent poly(3,4‐ethylene dioxythiophene)–poly(p‐styrene sulfonate‐co‐acrylic acid sodium) film with a high stability and water resistance

Poly(p‐styrene sulfonate‐co‐acrylic acid sodium) (PSA) from the copolymerization of acrylic acid sodium and p‐styrene sulfonate monomers were used to dope poly(3,4‐ethylene dioxythiophene) (PEDOT) to generate PEDOT–PSA antistatic dispersions. Compared to those of the PEDOT–poly(p‐styrene sulfonate sodium) (PSS), the physical and electrical properties of the PEDOT–PSA conductive liquids were much better. The PEDOT–PSA films possessed a better water resistance without a decrease in the conductivity. The sheet resistance of the PEDOT–PSA–poly(ethylene terephthalate) (PET) films was about 1.5 × 10⁴ Ω/sq with a 100 nm thickness, the same as the PEDOT–PSS–PET films. The transmittance of the PEDOT–PSA–PET films exceeded 88%. Furthermore, the environmental dispersity of the PEDOT–PSA antistatic dispersion was apparently improved by the dopant PSA so that the stability was extraordinarily promoted. Meanwhile, the water resistances of the PEDOT–PSA–PET and PEDOT–PSA films were also enhanced. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45163.     

Transparent Conducting Electrodes from Conducting Polymer Nanofibers and Their Application as Thin‐Film Heaters

Transparent conducting electrodes attract attention in relation to solar cells, touch panels, displays, e‐readers, and transparent heaters. In many cases, rarefied metal nets with optical transmittance of ≈90% and with minimal sheet resistance are sought after. Here, a mesh of conducting polymer nanofibers is developed as a transparent conducting electrode. A sheet resistance of 8.4 kΩ sq⁻¹ with 84% optical transmittance is achieved with polyethylene oxide/poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEO/PEDOT:PSS) blended polymer nanofibers. This study also demonstrates that such nanofiber being deposited on a glass substrate can be used as a transparent film heater in relevant applications such as window heating or displays at harsh environments. Such a transparent heater is rated at 0.41 W in.⁻² for 120 V. It is also capable of heating a substrate up to ≈70 °C in 4 min at 60 V from room temperature without any degeneration of nanofiber network, rendering itself as a practically useful transparent heater. The performance of the PEO/PEDOT:PSS nanofiber‐coated transparent glass heater is comparable to that of the relatively expensive indium tin oxide thin‐film heaters.     

Freeze-drying and mechanical redispersion of aqueous PEDOT:PSS

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films are attracting famous applications in antistatic coating, energy storage and conversion, printed electronics, and biomedical fields due to their conductivity, optical transparency and flexibility. However, PEDOT:PSS has poor dispersion stability during long-term storage and transport. Moreover, the dried PEDOT:PSS films are insoluble in any solvent and cannot be redispersed again. In comparison to bake drying, here, a feasible strategy to achieve mechanically redispersed PEDOT:PSS with the help of freeze-drying process was reported. The redispersed PEDOT:PSS can recover not only the initial characters such as pH, chemical composition, viscosity, and particle size under similar solid contents, but also conductivity and surface morphology of treated films. In addition, the treated film exhibits self-healing properties similar to pristine film in terms of mechanical and electrical properties. This technology enables reuse and overcomes the technical problems of PEDOT:PSS dispersion, realizing real-time processing to meet variable applications.     

Electrical conductivity enhancement of spin‐coated PEDOT:PSS thin film via dipping method in low concentration aqueous DMSO

The electrical conductivity of poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was enhanced by dipping the thin films prepared by spin coating technique in an aqueous DMSO solution. The low concentration range of DMSO in water between 0–5 vol % was studied in comparison with pure water and pure DMSO. It was found that the electrical conductivity dramatically increased as increasing the concentration of DMSO and reached the constant value of 350 S cm^?1 at 2 vol % of aqueous DMSO solution. This could be explained by the conformational change of PEDOT chains from the coil structure to the linear or expanded coil structure as confirmed by Raman spectra. Further, white patches were obviously noticed on the surface of the films dipped in pure DMSO, indicating the phase separation of conductive PEDOT grains and associated PSS. The sulfur element of the dipped film surface was investigated by XPS. The XPS S2p core‐level spectra displayed that the unassociated PSS was considerably removed from the surface of PEDOT:PSS films dipped in pure water and 2 vol % of aqueous DMSO solution, indicating that the presence of water in the solvents is important to prominently promote the washing effect. Finally, UV–Vis spectra revealed the improved transparency of the films probably owing to the decreased film thickness. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42108.     

Enhanced thermoelectric performance of poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) with long‐term humidity stability via sequential treatment with trifluoroacetic acid

This paper reports a range of effective sequential chemical processes to enhance the thermoelectric performance of conducting poly(3,4‐ethylenedioxythiophene) films doped with poly(styrene sulfonate) anions (PEDOT:PSS). The electrical conductivity of the PEDOT:PSS films was significantly increased from 0.33 to 3748 S cm^?1 after a series of sequential treatments with trifluoroacetic acid (TFA) while the Seebeck coefficient and thermal conductivity were slightly reduced from 17.5 ± 1.2 to 16.0 ± 1.1 μV K^?1 and 0.537 to 0.415 W m^–1 K^?1 for the pristine film and treated film, respectively, leading to a significant improvement in power factor up to 97.1 ± 5.4 μW m^–1 K^?2. More importantly, around 80% of the electrical conductivity and Seebeck coefficient was retained after 20 days for these TFA‐treated PEDOT:PSS films, revealing the potential for real thermoelectric applications. © 2019 Society of Chemical Industry     

Electromagnetic interference shielding properties of PEDOT/PSS–halloysite nanotube (HNTs) hybrid films

Poly(3,4‐ethylenedioxythiophene)/poly(4‐styrene sulfonate) (PEDOT/PSS) films hybridized with halloysite nanotubes (HNTs) were for the first time investigated for electromagnetic interference (EMI) shielding. The hybridization of the HNTs induced EMI properties for the pristine PEDOT/PSS films, and the content of the HNTs in the hybrid films significantly influenced the EMI properties of the hybrid films. The highest EMI shielding effectiveness of the hybrid film is ?16.3 dB in the measured frequency range from 2 to 13 GHz for the PEDOT/PSS film hybridized with 75% HNTs, using a sample with 4.5 mm thick. The contribution of EMI shielding effectiveness in the hybrid films is mainly due to dielectric loss rather than magnetic loss. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44242.     

A PSS‐Free PEDOT Conductive Film Supported by a Hierarchical Nanoporous Layer Glass

The importance of transparent conductive film is increasing due to its use in applications such as touch‐panel devices. Although indium tin oxide is widely used because of its high conductivity and transparency, conductive polymers are being studied as alternative materials that avoid the use of rare metals and the brittleness associated with existing systems. Polyethylene dioxythiophene (PEDOT)/polyethylene sulfonic acid (PSS) is drawing a lot of attention due to its well‐balanced conductivity, transparency, film formability, and chemical stability. The nonconductive PSS reportedly covers the conductive PEDOT. The PSS shell provides carrier and film‐formability to PEDOT but is also a barrier that hinders electrical conductivity. Therefore, the PEDOT film formability is explored supported by a substrate without the addition of PSS. The “hierarchical nanoporous layer glass” holds the PSS‐free PEDOT with its nanopores to form a homogeneous, transparent film. The PSS‐free PEDOT film thus achieves transparency of over 85% and resistivity of below 500 Ω sq^?1.     

Microstructured conducting polymer coatings on plastic strip for contact electrodes: Formulation and tuning of sheet resistance

Mechanically strong and flexible strips of cellulose acetate were used to support a thin coating of poly(3,4 ethylenedioxythiophene) : poly(styrene sulfonic acid) PEDOT : PSS, an intrinsically conducting polymer (ICP), formulated with an aqueous dispersion of judiciously chosen copolymer of vinyl acetate and ethylene (VAE), to impart adhesion of the coating onto the substrate. Incorporation of a few drops of an organic acid to the formulation resulted in a substantial reduction of the sheet resistance of the coated surface. When the coated strips were post‐treated with a salt solution, a further fine tuning of the sheet resistance by a factor of 10 was achieved. The coated strips combine high conductivity with flexibility and mechanical strength. The performance of the coated strips has been evaluated in relationship to composition, coating thickness, and sheet resistance for application as contact electrodes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 234–237, 2007     

Electrically controlled cellular migration on a periodically micropatterned PEDOT:PSS conducting polymer platform

In the field of tissue engineering, the study of cellular adhesion and migration is of crucial interest. Conducting polymers such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) provide an outstanding interface with biology due to their soft nature, which is closer to the mechanical, chemical, and morphological properties of biological systems. In this work, periodically micropatterned PEDOT:PSS thin films are used as a platform to investigate cellular migration. Human cerebral microvascular endothelial cells (hCMEC) show alignment and linear motion along PEDOT:PSS microstripes of varying widths (10–30 μm). In addition, an electrochemical gradient is created on the PEDOT:PSS film along these microstripes to influence the cell behavior. hCMEC cells linearly change their velocities depending on the redox state of the conducting polymer film. This work demonstrates the potential of such conducting polymer platforms to combine, at the same time, several key physicochemical factors for controlling cellular migration. In the future, we envision that these conducting polymer platforms will deliver tools for tissue regeneration and lead to new opportunities in regenerative medicine. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47029.     

Synthesis of PEDOT:PSS (poly(3,4‐ethylenedioxythiophene))/poly(4‐styrene sulfonate))/ ngps (nanographitic platelets) nanocomposites as chemiresistive sensors for detection of nitroaromatics

Polymer nanocomposites (NCs) are a special class of materials having unique properties and wide application potential in electronics and other diverse areas. In this study, NCs consisting of poly(3,4‐ethylenedioxythiophene)/poly(4‐styrene sulfonate) (PEDOT:PSS) matrix reinforced with graphite nanosheets were fabricated by solution method. The graphite used was functionalized before fabrication of NCs. The functionalized graphite was characterized by transmission electron microscopy (TEM) and Fourier transform Infrared spectroscopy (FTIR) technique. The NCs prepared were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and FTIR technique. The conductivity studies of the prepared NCs were carried out. The prepared NCs films were investigated for the detection of nitrobenzene vapors. The detection mechanism is based on measuring resistivity changes that occur in a NC due to the absorption of nitrobenzene vapors by PEDOT:PSS film. These sensors exhibited excellent response at room temperature when exposed to vapors of nitrobenzene. Sensitivity as high as 18.5% was observed for PEDOT:PSS/NGPs composite. The chemresistor exhibits a fast response (～1.14 min) and good recovery time (～1–2 min). The response of NC to the nitrobenzene vapors is reproducible. POLYM. ENG. SCI., 53:2045–2052, 2013. © 2013 Society of Plastics Engineers     

Surface modification of linear low‐density polyethylene film by amphiphilic graft copolymers based on poly(higher α‐olefin)‐graft‐poly(ethylene glycol)

In this article, a series of amphiphilic graft copolymers, namely poly(higher α‐olefin‐co‐para‐methylstyrene)‐graft‐poly(ethylene glycol), and poly(higher α‐olefin‐co‐acrylic acid)‐graft‐poly(ethylene glycol) was used as modifying agent to increase the wettability of the surface of linear low‐density polyethylene (LLDPE) film. The wettability of the surface of LLDPE film could be increased effectively by spin coating of the amphiphilic graft copolymers onto the surface of LLDPE film. The higher the content of poly(ethylene glycol) (PEG) segments, the lower the water contact angle was. The water contact angle of modified LLDPE films was reduced as low as 25°. However, the adhesion between the amphiphilic graft copolymer and LLDPE film was poor. To solve this problem, the modified LLDPE films coated by the amphiphilic graft copolymers were annealed at 110° for 12 h. During the period of annealing, heating made polymer chain move and rearrange quickly. When the film was cooled down, the alkyl group of higher α‐olefin units and LLDPE began to entangle and crystallize. Driven by crystallization, the PEG segments rearranged and enriched in the interface between the amphiphilic graft copolymer and air. By this surface modification method, the amphiphilic graft copolymer was fixed on the surface of LLDPE film. And the water contact angle was further reduced as low as 14.8°. The experimental results of this article demonstrate the potential pathway to provide an effective and durable anti‐fog LLDPE film. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of polymer–nanoclay conductive nanocomposites

Polymer–clay nanocomposites based on poly(3,4‐ethylenedioxythiophene)/polystyrene sulfonate (PEDOT) : PSS and nanoclay montmorillonite were synthesized and characterized. The doping of PEDOT with polystyrene sulfonate made it water dispersible (PEDOT–PSS). Sodium dodecyl benzene sulfonate (SDBS) and ionic liquid were used to increase the interlayer spacing and the conductivity of the nanocomposites, respectively. The nanocomposite was characterized by various techniques, such as X‐ray diffraction (XRD), TEM, surface resistivity, and thermogravimetric measurement analysis. Interlayer spacing increased as a result of the addition of SDBS, and this was confirmed by the 2θ shift observed via XRD analysis. The surface morphology of the conductive coated clay was examined by TEM analysis. Good electrical surface conductivity, interlayer spacing, and polymer coating were observed for the material prepared using the surfactant and conductive ionic liquid. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface,interface and electronic properties of F8:F8BT polymeric thin films used for organic light‐emitting diode applications

Ultrathin polymeric films consisting of poly(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl) (F8) blended with poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole) (F8BT) grown onto PEDOT:PSS/ITO/PET were investigated by X‐ray photoelectron spectroscopy (XPS), depth‐profiling XPS, reflection electron energy loss spectroscopy (REELS) and angle‐dependent X‐ray absorption spectroscopy (XAS) to gain information on the films' electronic, order and interface properties. AFM studies provide valuable information on the films' nanotopographical properties and homogeneity. Spectroscopic ellipsometry and photoluminescence spectroscopy were used also to obtain information on the optoelectronic properties. Well‐ordered films were observed from the XAS analysis, measured at the sulfur K absorption edge. XPS measurements demonstrated that the surface composition of the polymer thin films prepared by a spin‐coating wet‐chemical deposition method matches the expected F8:F8BT blend stoichiometry. The interfacial properties were studied through an argon ion sputtering process coupled to the XPS acquisition, showing an enhancement of oxygen components at the interface. The films' inhomogeneity was verified by AFM images and analysis. We obtained a value of 3.1 eV as the electronic bandgap of the F8:F8BT film from REELS data, whereas analysis of the spectroscopic ellipsometry spectra revealed that the optical bandgap of F8:F8BT has a value of 2.4 eV. A strong green emission was obtained for the produced films, which is in agreement with the expected emission due to the 1:19 ratio of the F8 and F8BT blended polymers. © 2018 Society of Chemical Industry     

Hole transport in conducting ultrathin films of PEDOT/PSS prepared by layer-by-layer deposition technique

Multilayered ultrathin films of a conductive polymer, poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) were prepared by layer-by-layer deposition technique. These films were characterized by absorption spectroscopy, atomic force microscopy, cyclic voltammetry and potential step chronoamperometry. The PEDOT/PSS films were layered up with a bilayer thickness of 5 nm and the surface roughness of the films was improved after the ultrasonicated pretreatment of a PEDOT/PSS aqueous dispersion prior to the deposition. The ultrathin films thus obtained kept excellent diffusion constant of hole carriers, 5×10⁻¹⁰ cm² s⁻¹, as high as that of spin-cast films of PEDOT/PSS, indicating that the conducting polymer films are fabricated with nanometer-scale precision and act as a junction layer between the electrode and electrochemically active organic materials.     

Morphology,order, light transmittance,and water vapor permeability of aluminum‐coated polypropylene zeolite composite films

In this study, the polypropylene–zeolite composite films having 2–6 wt % natural zeolite were coated with a thin film of aluminum (Al) by magnetron sputtering, and the contribution of the Al coating on film properties was investigated. The samples were characterized by EDX, X‐ray diffraction, SEM, AFM, UV–visible spectroscopy, and water vapor permeation analyses. The surface of the films coated with a smooth Al film having 98–131 nm thickness. EDX revealed that Al percentage on the surface appeared to be as 8–10 wt % indicating contribution of polymer surface under Al film to analysis. XRD analysis showed that the grain size of Al at the surface was 22–29 nm. The surface roughness increased after Al‐coating process. The transmission of coated films was very low for both UV and visible regions of the light spectrum. Permeation analysis indicated that water vapor permeation was lower for Al‐coated material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characterization of antireflective coatings on poly(methyl methacrylate) substrate by different process parameters

The high/low refractive index organic/inorganic antireflective (AR) hybrid polymers were formed using the sol–gel process, in which TiO₂/2‐hydroxyethyl methacrylate (2‐HEMA) (high refractive index hybrid polymer) and SiO₂/2‐HEMA (low refractive index hybrid polymer) two‐layer thin films were formed on a hard coating deposited poly(methyl methacrylate) (HC‐PMMA) substrate by both spin coating and dip coating. The relationship between the process parameters and the optical properties, thickness, porosity, surface morphology, and adhesion was determined. The results show that the reflectance of the two‐layer thin films on HC‐PMMA substrate is less than 0.21% (λ = 550 nm), with good adhesion (5B) and a hardness of up to 4H. In addition, the thickness, porosity, and roughness of the films affect refractive index and the antireflection properties of the AR two‐layered thin film. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013