Photopolymerized silver-containing conducting polymer films. Part I. An electronic conductivity and cyclic voltammetric investigation

A photopolymerization process that simultaneously deposits electronically conducting polymer films and incorporates nanophase silver grains within the films, the silver grains having been formed in situ on irradiating cast, photopolymerizable formulations containing silver salts, was developed. Polymer films produced from formulations containing large organic anions were very flexible and strongly adherent to substrates. Polypyrrole films containing silver grains were characterized electronically on measuring their electronic conductivities and electrochemically on recording their cyclic voltammetric profiles. Conductivities were affected by the chemical identity and concentration of components added to photopolymerizable formulations. The best photopolymerized films had a conductivity of the order of 1 S cm⁻¹. Electronically conducting films derived from formulations consisting of a monomer, an electron acceptor/“dopant,” and a photoinitiator were electrochemically active. They possessed long-term stability under extended electrode potential cycling conditions, acceptable charge storage capacity, and the ability to oxidize or reduce redox couples in solution. Paper submitted for inclusion in the special issue of the Journal of Solid State Electrochemistry honouring the 85th birthday of Professor John O’M. Bockris.     

In situ film characterization of thermally treated microstructured conducting polymer films

Based on a low‐cost fabrication routine microstructured conducting polymer films of poly (dioctylfluorene‐co‐benzothiadiazole) (F8BT) are prepared without any heat treatment or vacuum steps. The influence of thermal annealing at temperatures below the glass transition temperature of F8BT on such microstructured channel structures is investigated. In the applied structuring routine, a F8BT film is spin coated on a channel‐type hard master structure and afterwards floated on a flat support. Thereby, the properties of the final polymeric structures, for example channel width and height, can be tuned by simply varying the polymer concentration in solution and using the same master structure. With in situ grazing incidence small angle X‐ray scattering and imaging ellipsometry the installed channel structure and the influence of thermal treatment are probed. A complex interplay between a macroscopic polymer flow (reduced channel heights) and a molecular rearrangement (formation of mesoscopic crystallites) takes place during thermal annealing. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Synthesis and characterization of thiazolothiazole‐based polymers and their applications in polymer solar cells

A novel series of thiazolothiazole (Tz)‐based copolymers, poly[9,9‐didecylfluorene‐2,7‐diyl‐alt‐2,5‐bis‐(3‐hexylthiophene‐2‐yl)thiazolo[5,4‐d]thiazole] (P1), poly[9,9‐dioctyldibenzosilole‐2,7‐diyl‐alt‐2,5‐bis‐(3‐hexylthiophene‐2‐yl)thiazolo[5,4‐d]thiazole] (P2), and poly[4,4′‐bis(2‐ethylhexyl)‐dithieno[3,2‐b:2′,3′‐d]silole‐alt‐2,5‐bis‐(3‐hexylthiophene‐2‐yl)thiazolo[5,4‐d]thiazole] (P3), were synthesized for the use as donor materials in polymer solar cells (PSCs). The field‐effect carrier mobilities and the optical, electrochemical, and photovoltaic properties of the copolymers were investigated. The results suggest that the donor units in the copolymers significantly influenced the band gap, electronic energy levels, carrier mobilities, and photovoltaic properties of the copolymers. The band gaps of the copolymers were in the range of 1.80–2.14 eV. Under optimized conditions, the Tz‐based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range of 2.23–2.75% under AM 1.5 illumination (100 mW/cm²). Among the three copolymers, P1, which contained a fluorene donor unit, showed a PCE of 2.75% with a short‐circuit current of 8.12 mA/cm², open circuit voltage of 0.86 V, and a fill factor (FF) of 0.39, under AM 1.5 illumination (100 mW/cm²). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of magnetoelectric polymer nanocomposites

Magnetoelectric polymer nanocomposite structures are synthesized using conducting polyaniline and nanosized BFO particles through in situ sol–gel polymerization. The effect of nanosized BFO in polyaniline matrix is studied. The SEM, XRD, VSM, FTIR, and UV–Vis studies were made to understand the morphology, crystalline structure, magnetic, and optical properties of PANI/BFO composites with various concentrations of nanofiller. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2418–2422, 2008     

Temperature diffusivity and heat conductivity of Langmuir–Blodgett–Kuhn and thin spun-on polymer films

The temperature diffusivity β and heat conductivity κ of thin polymer films were measured at room temperature. Temperature waves were excited at one side of the film and detected at the other side with a pyroelectric foil (PVDF). The dependence of β and κ on chemical and structural parameters have been studied. For the first time, Langmuir–Blodgett–Kuhn multilayer assemblies prepared from “hairy rod” polymers were characterized: μm thin films of stiff polyamides prepared by spincoating exhibit heat conductivities an order of magnitude larger than “classical” polymers.     

Preparation and characterization of poly-N-vinyl carbazole langmuir-blodgett films

Langmuir monolayers of poly-N-vinyl carbazole (PNVK) were obtained by dispensing PNVK dissolved in tetrahydrofuran onto an air-water interface. Surface pressure-area isotherms of mixed monolayer of the PNVK were studied under different subphase conditions such as temperature and pH of the subphase. It was demonstrated that the monolayer of PNVK remained stable over a temperature range of 10–40°C. The area per molecule of the solid phase was found to be 31Ų. These monolayers were transferred onto indium-tin-oxide-coated glass plates and characterized by spectroscopic and electrochemical techniques.     

Synthesis and characterization of poly(N‐isopropylacrylamide) films by photopolymerization

A novel method used for the preparation of poly(N‐isopropylacrylamide) (PNIPAAm) films of varying crosslink density under homogeneous/heterogeneous conditions is described in this paper. Photopolymerization of the N‐isopropylacrylamide (NIPAAm) monomer in water (homogeneous at ～7°C and heterogeneous at ～40°C) or a mixture of water/ethanol (50:50, heterogeneous at ～7°C) was carried out using 1‐[4‐(2‐hydroxyethoxy)‐phenyl]‐2‐hydroxy‐2‐methyl‐1‐propane‐1‐one (hydrophilic) or 2‐hydroxy‐2‐methyl propiophenone (hydrophobic) photo‐initiator. In order to investigate the effect of temperature and crosslink density, polymerization was carried out at ～7°C [below lower critical soluble temperature (LCST)] and ～40°C (above LCST) using varying amounts of N,N′‐methylene bisacrylamide (BIS) ranging from 1–4 wt%. Degree of swelling (determined by optical microscopy), phase transition temperature [determined by differential scanning calorimetry (DSC)] as well as morphology (scanning electron microscopy) were found to be dependent on solvent system (homogeneous/heterogeneous), temperature of polymerization and crosslink density. Hydrogels prepared at ～7°C using hydrophobic photo‐initiator and water/ethanol (50:50) as solvent, showed much higher degree of swelling at all levels of crosslink density as compared to hydrogel prepared at ～7°C using hydrophilic photo‐initiator and water as solvent. Hydrogels were used for patterning which may find applications in microfluidic devices. Copyright © 2006 John Wiley & Sons, Ltd.     

Novel conducting polymer poly[bis(phenylamino)disulfide]: Synthesis,characterization, and properties

A bis(phenylamino)disulfide was prepared through the reaction of S₂Cl₂ with aniline, and its configuration was confirmed with elemental analysis, Fourier transform infrared (FTIR), Fourier transform Raman (FT‐Raman), and ¹H NMR spectroscopy. A novel conducting polymer, poly[bis(phenylamino)disulfide] (PPAD), was synthesized from bis(phenylamino)disulfide by both chemical and electrochemical polymerization. The structure of this polymer, in which the side‐chain disulfide bonds were linked to the nitrogen atoms of the main‐chain polyaniline, was characterized with FTIR, FT‐Raman, gel permeation chromatography, electron spectroscopy, and X‐ray photoelectron spectroscopy. A four‐probe measurement revealed that the electrical conductivity of PPAD was 1.8 × 10^?2 to 2.1 × 10^?3 S cm^?1, depending on the doping agents and the pH of the medium for either chemical synthesis or electrochemical synthesis. The conductivity, molecular weight, and spectroscopic properties of the polymer, in comparison with those of polyaniline, showed decreases in the polaron delocalization, structural order, and doping level of the main chain because of the steric hindrance of side‐chain S? S bonds. The cyclic voltammograms of the polymer and the monomer showed that the redox reactions (doping/undoping processes) of the main chain (π‐conjugated system) occurred in almost the same potential range of ?0.3 to 0.3 V versus an Ag/AgCl (saturated KCl) electrode as that of thiol (thiolate anion)/disulfide of the side chain in PPAD; the bond cleavage (reduction) and formation (oxidation) reactions of the disulfide bond in the polymer became easier and more reversible than those of the monomer. These results suggested that this conducting organodisulfide polymer might be a candidate material for energy‐storage devices such as lithium secondary batteries, proton‐exchange batteries, and electrochemical capacitors. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2329–2339, 2004     

Multilayer films composed of conductive poly(3‐hydroxybutyrate)/carbon nanotubes bionanocomposites and a photoresponsive conducting polymer

In order to develop new electronic devices, it is necessary to find innovative solutions to the eco‐sustainability problem of materials as substrates for circuits. We realized a photoresponsive device consisting of a semiconducting polymer film deposited onto optically semitransparent and conductive biodegradable poly(3‐hydroxybutyrate) (PHB)/carbon nanotube (CNT) substrates. The experiments indicated that the PHB‐CNT bionanocomposite substrate behaves as an optical window trapping electric charges produced by the photoexcitation of the semiconducting polymer. Such PHB‐CNT functional substrates are expected to be attractive for eco‐friendly electronics. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 596–602     

Linked crystallites in the conducting topmost layer of polymer bilayer films controlled by temperature: from micro- to nanocrystallites.

Temperature has great impact on the structure and size of the linked crystallites of the conducting topmost layer formed at the surface of a polycarbonate film via the reaction BEDT-TTF+IBr [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene]. We show that fine temperature control permits formation of a semiconducting topmost layer of alpha'-(BEDT-TTF)(2)(I(x)Br(1-x))(3) crystallites with either micro- or nanometre size, a result that opens a route to miniaturized conducting plastic materials.     

Preparation and properties of ionic‐liquid‐containing poly(ethylene glycol)‐based networked polymer films having lithium salt structures

Ionic‐liquid‐containing polymer films were prepared by swelling poly(ethylene glycol)‐based networked polymers having lithium salt structures with an ionic liquid, 1‐ethyl‐3‐methylimidazolium bis(fluorosulfonyl)imide (EMImFSI), or with an EMImFSI solution of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI). Their fundamental physical properties were investigated. The networked polymer films having lithium salt structures were prepared by curing a mixture of poly(ethylene glycol) diglycidyl ether and lithium 3‐glycidyloxypropanesulfonate or lithium 3‐(glycidyloxypropanesulfonyl)(trifluoromethanesulfonyl)imide with poly(ethylene glycol) bis(3‐aminopropyl) terminated. The obtained ionic‐liquid‐containing films were flexible and self‐standing. They showed high ionic conductivity at room temperature, 1.16–2.09 S/m for samples without LiTFSI and 0.29–0.43 S/m for those with 10 wt % LiTFSI. Their thermal decomposition temperature was above 220 °C, and melting temperature of the ionic liquid incorporated in the film was around ?16 °C. They exhibited high safety due to good nonflammability of the ionic liquid. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Facile electrosyntheses of high tensile strength alkyl‐bridged dicarbazole polymer films and its fluorescence spectra

Homogeneous and high‐quality free‐standing poly(1,6‐bis(carbazolyl) hexane) (P2Cz‐H) and poly(1,12‐bis(carbazolyl)dodecane) (P2Cz‐D) films were electrochemically synthesized in CH₂Cl₂ + 0.1 M tetrabutylammonium tetrafluoroborate solution. The electrochemical and physical properties indicated that the quality of P2Cz‐D film with tensile strength of 165 kg cm⁻² was better than that of P2Cz‐H due to the flexible monomer 1,12‐bis(carbazolyl)dodecane (2Cz‐D) has a longer carbon chain than that of monomer 1,6‐bis(carbazolyl)hexane (2Cz‐H). On the other hand, both the dicarbazole monomers showed better polymer‐film‐forming capabilities than the single carbazole monomer, partly because of the special design of the polymer backbone constituted of stiff bicarbazyl chromophores linked by flexible long carbon segments. The structures of both dicarbazole polymers were investigated by UV–visible, infrared spectroscopy and scanning electron microscopy. Fluorescence spectral studies revealed that the two dedoped polymer films in solid state had strong emissions at ca. 411 and 415 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5232–5241, 2008     

Dielectric and optical properties of BaTiO<Subscript>3</Subscript> thin films prepared by low-temperature process

Barium titanate (BaTiO₃) thin films have been prepared by low temperature processing on Pt/Ti/SiO₂/Si substrates using sol-gel-hydrothermal (SGHT) technique, which combined the conventional sol-gel process and hydrothermal method. X-ray diffraction analysis showed that the barium titanate thin films are polycrystalline. As-reacted barium titanate films grown on Pt(111)/Ti/SiO₂/Si(100) substrates had a dielectric constant (ε) and loss tangent (tanδ) of 80 and 0.05 at 1 MHz, respectively. The optical constants including refractive index n, extinction coefficient k, and absorption coefficient α of the barium titanate thin films in the wavelength range of 2.5–12.6 μm were obtained by infrared spectroscopic ellipsometry.     

Hybrid organic/inorganic films of conducting polymers modified with phthalocyanines. II. EIS studies and film characterization

Conducting polymers were modified with Cu-phthalocyanine or Co-phthalocyanine embedded in a sol–gel matrix. The resulting films were characterized using electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. Electrochemical impedance spectroscopy data showed that the application of the sol–gel layer to the conductive polymer caused a noticeable increase in the impedance of the film across the frequency ranges studied. The hydrophobic character of the film was greatly influenced by the sol–gel and caused an increase in its capacitance. A modified ‘Randles’ equivalent cell was used to correlate the electrochemical parameters of the films. Elemental analysis and infrared data confirmed the presence of the phthalocyanine moieties in the film and the empirical formula of the film was estimated. The surface morphology of the sol–gel-modified conducting polymer was distinctly amorphous compared to the poly(3-methyl thiophene).     

Preparation and characterization of poly(phthalazinone ether ketone)/SiO<Subscript>2</Subscript> hybrid composite thin films with low friction coefficient

Organic–inorganic poly(phthalazinone ether ketone) (PPEK)/SiO₂ hybrid composite thin films were prepared by the dip-coating method on pre-cleaned glass substrates. The covalent bonds between organic and inorganic phases were introduced by an in-situ O-acylation reaction of isocyanatopropyltriethoxysilane (ICPTES) with the borohydride-reduced PPEK forming a polymer bearing triethoxysilyl groups. Theses groups were subsequently hydrolyzed with tetraethoxysilane (TEOS) and allowed to form a network via a sol–gel process. The polymer hybrid composite exhibited good thermal stability and a higher glass transition temperature as compared with the pure resin. Atomic force microscope, water contact angle measurement and scanning electron microscope were used to characterize the polymer hybrid thin films. The tribological experiment showed that the films have very low friction coefficient (about 0.1) and good anti-wear properties, without failure even after sliding for 18,000 s under modest loads. The improved tribological properties of the modified substrate were attributed to good adherence of PPEK/SiO₂ hybrid films on the substrate and synergy of both PPEK matrix and silica particles.     

Preparation of conducting poly(vinyl chloride)/polyindole composites and freestanding films via chemical polymerization

This study covers the synthesis of conducting polyindole (PIN) homopolymer, poly(vinyl chloride)/polyindole (PVC/PIN) composites, and preparation of their freestanding films. PIN and composites were synthesized chemically by radicalic mechanism using FeCl₃ as an initiator. Films of PVC and PVC/PIN composites were prepared by casting on glass Petri dishes. Mechanical properties of films were examined by stress–strain experiments. From FTIR spectra of polymers, it was revealed that polymerization reaction occurred by 2–3 mechanism. The conductivities of polymers at different temperatures were also measured by four‐probe technique and found in the range 10^?4 to 10^?5 S cm^?1. Magnetic properties of the polymers were analyzed by Gouy scale measurements and were found that their conducting mechanisms are of polaron and bipolaron natures. Thermal properties of polymers were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and found that they had shown adequate thermal stability. X‐ray diffraction (XRD) spectra showed the amorphous nature of the polymers. Scanning electron microscopy (SEM) was used for microstructural analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1290–1298, 2010     

Improved microwave absorption and electrostatic charge dissipation efficiencies of conducting polymer grafted fabrics prepared via in situ polymerization

Polyaniline (PANI) and polypyrrole (PPY) were grafted over cotton fabrics by in situ polymerization. FTIR spectra show systematic shifting of bands corroborating surface grafting of conducting polymers on cotton fabric. SEM images revealed that the surface coating of PANI was smoother than PPY. However, better control over coating thickness and uniformity was achieved in PPY fabric. The probable formation mechanism of grated fabrics has also been proposed. The good thermal stability and acceptable electronic conductivity values indicate that these fabrics could be used for electrostatic charge dissipation and microwave absorption. The antistatic studies have shown complete charge dissipation (decay time <0.01 sec). The microwave absorption studies of the conducting fabrics in X‐band (8.2–12.4 GHz) show absorption dominated total shielding effectiveness in the range ?11.3 to ?11.7 dB (>92% attenuation) and ?9.2 to ?9.6 dB (>88% attenuation) for fabrics grafted with PPY and PANI, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

NMR study of the nanomorphology in thin films of polymer blends used in organic PV devices: MDMO‐PPV/PCBM

The disclosure of the nanomorphology of thin films in organic solar cells, prepared from blends of conjugated polymers and PCBM, is of key importance for a better understanding of the occurring photovoltaic (PV) mechanisms. Hereto solid‐state NMR relaxometry has been evaluated as a complementary technique to traditional microscopic techniques like atomic force microscopy and transmission electron microscopy. It is demonstrated that proton wide‐line solid‐state NMR relaxometry is a useful and innovative tool to study the phase morphology of blends used in semi‐conducting polymer based PV devices. Attention is focused on the influence of the blend composition and casting conditions on the resulting phase morphology. Two different casting techniques, i.e. spincoating and Doctor Blading, were compared. To demonstrate the applicability of NMR relaxometry in this field, MDMO‐PPV/PCBM blends where used, since these are known for their significant phase separation behavior in combination with toluene as solvent. In films prepared from blends in toluene with a PCBM content ≥70 wt %, a fraction of the PCBM is phase separated into crystalline domains, whereas the remaining part remains homogeneously mixed with the MDMO‐PPV. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 138–145, 2008     

Metal‐conducting polymer interface studied by Kelvin probe microscopy: Au and Al on poly(3‐octyl‐thiophene)

In this work, we report a Kelvin probe microscopy investigation on the structural and electronic properties of gold and aluminum thin films evaporated on poly(3‐octyl‐thiophene) films. Our experimental setup allows us to perform scanning force microscopy (SFM) studies of the same area even if the sample is taken out of the SFM system for different processes (Au and Al evaporation). This allows a detailed study of the effect of adsorbed metal particles on the morphology and electrical properties of polymer thin films at the nanoscale. We found different behavior for both metals in morphology and electrical properties at the interface. These results can contribute to explain what happens at the metal–polymer interface of the devices when the metal contacts are grown. Thereby the observed nanoscale structural changes can be correlated with the overall performance of the fabricated devices. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1083–1093     

Synthesis,characterization, and application to polymer solar cells of polythiophene derivatives with ester‐ or ketone‐substituted phenyl side groups

Four polythiophene derivatives including regiorandom polymers P1 , P2 , and P3 and a regioregular polymer P4 , containing a phenyl side chain with electron‐withdrawing carbonyl groups such as an ester and a ketone at the 3‐position of the thiophene ring, were synthesized by Stille coupling reaction. Bulk‐heterojunction polymer solar cells (PSCs) based on these polymers as p‐type semiconductors and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) were fabricated, and their photovoltaic performances were evaluated for the first time. The PSC devices based on the regioregular polymer P4 :PCBM = 1:2 (w/w) exhibited a high‐open‐circuit voltage (V_oc) of 0.943 V because of the low‐lying highest occupied molecular orbit energy level of P4 . The short π–π stacking distance (0.355 nm) in the parallel direction to the substrate and “face‐on” rich orientation were observed by the grazing incidence wide‐angle X‐ray scattering experiment, which might reflect higher J_sc and FF values of the P4 :[6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) PSC device than others. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 875–887