Influence of polymer particle size on the percolation threshold of electrically conductive latex‐based composites

Monodispersed copolymer emulsions, each with a different polymer particle size, were used to investigate the effect of particle size on the electrical and thermomechanical properties of carbon black (CB)‐filled segregated network composites. These emulsions were synthesized with equal moles of methyl methacrylate and butyl acrylate, with latex particle size ranging from 83 to 771 nm. The electrical percolation threshold was found to decrease from 2.7 to 1.1 vol % CB as the latex particle size was increased. Microstructural images reveal diminished latex coalescence, and improved CB segregation, with increasing latex particle size. In general, coalescence is shown to increase for all systems with increasing CB concentration. Furthermore, all systems exhibited a similar maximum electrical conductivity plateau of 0.7 S cm^?1, albeit at lower concentration for larger latex particle size. This ability to tailor percolation threshold with latex particle size provides an important tool for manipulating electrical and mechanical properties of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1547–1554, 2011     

A mixed‐valence complex of cobalt based on 3‐methoxysalicylaldoxime

A new tetranuclear mixed‐valence cobalt complex, namely di‐μ₂‐azido‐diazidodiethanolbis{μ₂‐2‐[(hydroxyimino)methyl]‐6‐methoxyphenolato}bis{μ₃‐6‐methoxy‐2‐[(oxidoimino)methyl]phenolato}dicobalt(II)dicobalt(III) ethanol disolvate, [Co^II₂Co^III₂(C₈H₇NO₃)₂(C₈H₈NO₃)₂(N₃)₄(C₂H₅OH)₂]·2C₂H₅OH, has been synthesized by the reaction of Co(OAc)₂·4H₂O (OAc is acetate) with 3‐methoxysalicylaldoxime (H₂mosao) in an ethanol solution. In the complex, the four Co cations all display distorted octahedral coordination environments and they are bridged by two κ²,κ¹,κ¹;μ₃‐mosao²⁻ ligands, two κ²,κ²;μ₂‐Hmosao⁻ ligands and two μ₂‐N₃⁻ anions to form a tetranuclear [Co₄N₄O₄] cluster. Adjacent clusters are connected through weak C—H...N and C—H...O interactions, resulting in a two‐dimensional supramolecular network parallel to the ac plane. The magnetic properties of the complex have also been studied.     

An approach to one‐dimensional conductive polymer composites

A substantial approach to one‐dimensional (1D) electrically conductive composites was proposed which was based on the thermodynamic analysis of electric‐field‐induced particle alignment in a nonpolar thermoplastic polymer matrix. The process condition window was based on the real‐time exploration of dynamic percolation under different electric fields with carbon black (CB)‐filled polyethylene as a model. The CB content was the main factor of the process condition. Its upper limit was set as the critical percolation concentration at the thermodynamic equilibrium state without an electric field to eliminate the possibility of conductive network formation perpendicular to the electric‐field direction, whereas its lower limit the critical percolation concentration at the thermodynamic equilibrium state under a critical electric field (E*). A composite with CB content in this window, isothermally treated in an electric field not less than E*, showed conductivity in the electric‐field direction about 10⁵ times larger than that in the perpendicular direction. A 1D cluster structure in the direction of the electric filed was confirmed with scanning electron microscopy morphology observations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 184–189, 2005     

Hybrid metal–polymer composites from functional block copolymers

The combination of metals and polymers in hybrid materials is a research area of great current interest. A number of methods for controlling the positioning of metallic species within polymer matrices on the nanometer scale have been developed. This highlight focuses on the use of functional block copolymers for the localization of metal species, especially nanoparticles, on the nanometer scale through block copolymer phase segregation. Research from the author's group on the use of alkyne‐functional block copolymers for the preparation of cobalt‐containing materials is discussed in this context. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4323–4336, 2005     

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     

Synthesis of functionalized conducting polymer “polyanthranilic acid” using various oxidizing agents and formation of composites with PVC

Synthesis of carboxyl functionalized polyaniline (PANI) (polyanthranilic acid PANA) is reported based on our recent studies using various oxidizing agents. PANA was synthesized in acidic medium using ammonium peroxodisulfate, hydrogen peroxide, and potassium permanganate as oxidizing agents and their structural, electrochemical, and electrical properties are studied. A comparative study among the polymers formed by various oxidizing agents and also with PANI is made. Various possible oxidation states of PANA are discussed, with the help of electrochemical data. A composite of PANA and polyvinyl chloride (PVC) containing 20% PVC by weight is synthesized and used for the development of solid state pH electrode. The composite was synthesized to improve mechanical strength, stability, and restrict solubility. The pH sensor response is found to be reversible and linear in the pH range 1–7. PANA and PVC (20 wt%) based pH sensors show potential applications in development of pH transducers based sensors/biosensors. Copyright © 2010 John Wiley & Sons, Ltd.     

UV cured transparent films including non‐aqueous conductive microgels

UV cured transparent films containing non‐aqueous conductive microgels coated with poly(aniline)/dodecyl benzenesulfonic acid(DBSA) were obtained. The conductive microgels were prepared by interface polymerization of aniline/DBSA in the presence of non‐aqueous polymeric microgels. The electrical conductivity and the particle size of the prepared conductive microgel were 0.5 S/cm and 58 nm, respectively. The prepared conductive microgels were easily blended with a UV curable coating formulation, and then were cured to make highly optically transparent films. For the UV cured film containing about 35 wt% of the conductive microgels, a surface resistance in the range of 10⁷ to 10⁸ Ω/square was obtained. In a polar cosolvent, such as NMP and m‐cresol, the critical volume was shifted to the lower range, with a value of 10 wt%. The UV cured films containing the conductive microgels exhibited good electrical stability against the thermal aging and humidity. Copyright © 2002 John Wiley & Sons, Ltd.     

Thermoresponsive conductive polymer composite thin film and fiber mat: Crosslinked PEDOT:PSS and P(NIPAAm‐co‐NMA) composite

The thermoresponsive conductive composite (TCC) thin films and fiber mats, whose electrical property changed with temperature, were fabricated successfully. The thermocrosslinkable and thermoresponsive copolymer, poly(N‐isopropyl acrylamide‐co‐N‐methylolacrylamide) (PNN), was synthesized. The TCC thin film and fiber mat were fabricated by spin coating and electrospinning process of PEDOT:PSS/PNN solutions, respectively. After thermocrosslinking and doping by DMSO, the composite thin films and fiber mats were obtained. Fibrous structures of TCC fiber mats were observed by SEM. The surface resistance and conductivity of composites were measured. The thermoresponsivity and swelling ratio of TCCs were also studied. The thermoresponsive conductive property was analyzed by measuring the surface resistance of TCCs in water bath under various temperatures from 20 to 50 °C. With the increase of temperature, the TCCs shrank to be dense structure and showed lower surface resistance. The TCC fibers mat exhibited greater sensitivity to temperature than thin film owing to its fibrous structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1078–1087     

The preparation of polyaniline/polypyrrole conductive polymer films on polycarbonate‐coated Pt electrodes

In this study, free‐standing polymer films were obtained first with an electrochemical coating of polyaniline and then with a coating of polypyrrole on an insulating polycarbonate‐coated Pt electrode. The films contained varying amounts of polyaniline and polypyrrole obtained by varying the electrolysis time, and their conductivities were determined. The Raman spectra of the films taken from the electrode side were similar to those of pure polyaniline, whereas the spectra of the solution side were identical to those of pure polypyrrole. The resistance change in the films between −15 and +120°C revealed that the films were sensitive to temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 51–59, 2000     

Polyaniline‐tailored electromechanical responses of the silver/epoxy conductive adhesive composites

In this article, the electromechanical properties of silver‐in‐epoxy conductive adhesives with the polyaniline (PANI) micron particles as cofillers have been investigated. PANI is a conductive polymer and has a moderate conductivity in between those of silver and epoxy. It was found that PANI can be used to tailor both the adhesive's electrical contact resistance and its relaxation behavior; however, the effects of adding PANI were complex. The addition of small amount of PANI (2 wt %) dramatically increased the contact resistance; it might block the electrical contacts among silver flakes and was not able to form a continuous path among themselves. The addition of more PANI showed a moderate increase in contact resistance, which increased with the weight fraction of PANI from 6 to 15 wt %. Interdependent behavior of compressive strain and relaxation in electrical contact resistance is characterized to evaluate the origin of this relaxation. The addition of PANI made the relaxation in electrical contact resistance more sensitive to the compressive strain and the electromechanical coupling to deviate from the linear relationship. These research findings provide insights into the way to use PANI to tailor the electromechanical properties of the adhesive bonds or joints in the development of advanced functional devices. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013, 51, 1448–1455     

A two‐dimensional mixed‐valence CuII/CuI coordination polymer constructed from 2‐(pyridin‐3‐yl)‐1H‐imidazole‐4,5‐dicarboxylate

Coordination polymers are a thriving class of functional solid‐state materials and there have been noticeable efforts and progress toward designing periodic functional structures with desired geometrical attributes and chemical properties for targeted applications. Self‐assembly of metal ions and organic ligands is one of the most efficient and widely utilized methods for the construction of CPs under hydro(solvo)thermal conditions. 2‐(Pyridin‐3‐yl)‐1H‐imidazole‐4,5‐dicarboxylate (HPIDC²⁻) has been proven to be an excellent multidentate ligand due to its multiple deprotonation and coordination modes. Crystals of poly[aquabis[μ₃‐5‐carboxy‐2‐(pyridin‐3‐yl)‐1H‐imidazole‐4‐carboxylato‐κ⁵N¹,O⁵:N³,O⁴:N²]copper(II)dicopper(I)], [Cu^IICu^I₂(C₁₀H₅N₃O₄)₂(H₂O)]_n, (I), were obtained from 2‐(pyridin‐3‐yl)‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃PIDC) and copper(II) chloride under hydrothermal conditions. The asymmetric unit consists of one independent Cu^II ion, two Cu^I ions, two HPIDC²⁻ ligands and one coordinated water molecule. The Cu^II centre displays a square‐pyramidal geometry (CuN₂O₃), with two N,O‐chelating HPIDC²⁻ ligands occupying the basal plane in a trans geometry and one O atom from a coordinated water molecule in the axial position. The Cu^I atoms adopt three‐coordinated Y‐shaped coordinations. In each [CuN₂O] unit, deprotonated HPIDC²⁻ acts as an N,O‐chelating ligand, and a symmetry‐equivalent HPIDC²⁻ ligand acts as an N‐atom donor via the pyridine group. The HPIDC²⁻ ligands in the polymer serve as T‐shaped 3‐connectors and adopt a μ₃‐κ²N,O:κ²N′,O′:κN′′‐coordination mode, linking one Cu^II and two Cu^I cations. The Cu cations are arranged in one‐dimensional –Cu1–Cu2–Cu3– chains along the [001] direction. Further crosslinking of these chains by HPIDC²⁻ ligands along the b axis in a –Cu2–HPIDC²⁻–Cu3–HPIDC²⁻–Cu1– sequence results in a two‐dimensional polymer in the (100) plane. The resulting (2,3)‐connected net has a (12³)₂(12)₃ topology. Powder X‐ray diffraction confirmed the phase purity for (I), and susceptibilty measurements indicated a very weak ferromagnetic behaviour. A thermogravimetric analysis shows the loss of the apical aqua ligand before decomposition of the title compound.     

Syntheses of pyrimidine‐based polymers containing electron‐withdrawing substituent with high open circuit voltage and applications for polymer solar cells

Polymers using new electron‐deficient units, 2‐pyriminecarbonitrile and 2‐fluoropyrimidine, were synthesized and utilized for the photovoltaics. Donor‐acceptor (D‐A) types of conjugated polymers ( PBDTCN, PBDTTCN, PBDTF, and PBDTTF ) containing 4,8‐bis(2‐octyldodecyloxy)benzo[1,2‐b;3,4‐b′]dithiophene (BDT) or 4,8‐bis(5‐(2‐octyldodecyloxy)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene (BDTT) as electron rich unit and 2‐pyriminecarbonitrile or 2‐fluoropyrimidine as electron deficient unit were synthesized. We designed pyrimidine derivatives in which strong electron‐withdrawing group (C?N or fluorine) was introduced to the C2 position for the generation of strong electron‐deficient property. By the combination with the electron‐rich unit, the pyrimidines will provide low band gap polymers with low highest occupied molecular orbital (HOMO) energy levels for higher open‐circuit voltages (V_OC). For the syntheses of the polymers, the electron‐rich and the electron‐deficient units were combined by Stille coupling reaction with Pd(0)‐catalyst. Absorption spectra of the thin films of PBDTTCN and PBDTTF with BDTT unit show shift to a longer wavelength region than PBDTCN and PBDTF with BDT unit. Four synthesized polymers provided low electrochemical bandgaps of 1.56 to 1.96 eV and deep HOMO energy levels between ?5.67 and ?5.14 eV. © 2015 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 771–784     

Voltage‐induced resistivity relaxation in a high‐density polyethylene/graphite nanosheet composite

The resistivity relaxation behavior under applied voltages in a high‐density polyethylene/graphite nanosheet composite was investigated. The influence of applied voltages on the resistivity relaxation was measured by the collection of the electric current passing through the sample and the increasing temperature of the sample. With increments in the voltage, three distinguishable relaxation curves corresponding to different dominating mechanisms were observed. The sawed curve, corresponding to the application of a high voltage, could be attributed to the reorganization of conductive particles induced by the electric field and the destruction of the conductive network due to the thermal expansion of the high‐density polyethylene matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 860–863, 2007     

A one‐dimensional chloride‐bridged PtII/PtIV mixed‐valence complex with a 4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate counter‐ion

The title compound, catena‐poly[[[bis(ethylenediamine‐κ²N,N′)platinum(II)]‐ μ‐chlorido‐[bis(ethylenediamine)platinum(IV)]‐μ‐chlorido] tetrakis{4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate} dihydrate], {[Pt^IIPt^IVCl₂(C₂H₈N₂)₄](HOC₆H₄N=NC₆H₄SO₃)₄·2H₂O}_n, has a linear chain structure composed of square‐planar [Pt(en)₂]²⁺ (en is ethylenediamine) and elongated octahedral trans‐[PtCl₂(en)₂]²⁺ cations stacked alternately, bridged by Cl atoms, along the b axis. The Pt atoms are located on an inversion centre, while the Cl atoms are disordered over two sites and form a zigzag ...Cl—Pt^IV—Cl...Pt^II... chain, with a Pt^IV—Cl bond length of 2.3140 (14) Å, an interatomic Pt^II...Cl distance of 3.5969 (15) Å and a Pt^IV—Cl...Pt^II angle of 170.66 (6)°. The structural parameter indicating the mixed‐valence state of the Pt atom, expressed by δ = (Pt^IV—Cl)/(Pt^II...Cl), is 0.643.     

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     

The total Position Spread in mixed‐valence compounds: A study on the model system

The behavior of the Total Position Spread (TPS) tensor, which is the second moment cumulant of the total position operator, is investigated in the case of a mixed‐valence model system. The system consists of two H₂ molecules placed at a distance D. If D is larger than about 4 bohr, the singly ionized system shows a mixed‐valence character. It is shown that the magnitude of the TPS has a strong peak in the region of the avoided crossing. We believe that the TPS can be a powerful tool to characterize the behavior of the electrons in realistic mixed‐valence compounds. © 2014 Wiley Periodicals, Inc.     

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     

Preparation and characterization of biodegradable and electroactive polymer blend materials based on mPEG/tetraaniline and PLLA

A novel PGTA diblock copolymer containing electroactive TEA and mPEG is described. Biodegradable PLLA/PGTA polymer blends are shown to be electroactive. Nanopores of different sizes can be formed on the surface of the polymer blends. An MTT assay shows that the PLLA/PGTA blends exhibited reduced cytotoxicity as compared to TEA due to the introduction of the biocompatible PLLA moiety. Cell culture results show that the cells grow better when they were adhered to the surface of the PLLA/PGTA blends. The 80/20 wt.-% PLLA/PGTA blend shows the best biocompatibility and an electroactivity that accelerates the differentiation of rat C6 glioma cells.     

Filler size effects on the conductivity of polymer nanocomposites: Semiconductive phthalocyanine nanoparticles in epoxy matrices

Three Cobalt(III) phthalocyanine (Phthalcon) powders with different particle sizes and chemical compositions, but almost equal XRD spectra and powder conductivity were synthesized and used as conductive fillers in crosslinked epoxy matrices. Two of these Phthalcons are new compounds. The relation between the conductivity of the composites and the type and amount of filler used was determined. The influence of particle size and chemical composition on this relation appeared to be minimal. These composites had a percolation threshold of 0.9 vol % and a maximum volume conductivity of 10^?7 S/cm. Detailed analysis showed that the particle networks have very similar fractal structures and that they are likely to be formed by diffusion limited cluster‐cluster aggregation during processing. Evidence is presented that these particle networks are formed at an early stage of crosslinking and that the charge transfer between particles in the networks is neither limited by the Phthalcon particle size, nor by the presence of polymer matrix between the particles. The maximum volume conductivity of these composites is likely to be limited by the amount of filler used, the crystal structure defects on the particle surface, and the fractality and the imperfection of the particle networks. The impact of these findings on the conductivity of other polymer nanocomposites is discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1079–1093, 2008     

Synthesis of water‐soluble conductive copolymer based on polyaniline

Synthesis and characterization of polyaniline‐grafted poly(styrene‐alt‐maleic anhydride) (PANI‐g‐PSMA) was carried out to obtain conductive comb copolymers with highly improved processability. First, polyaniline (PANI) was prepared in nano‐scale by chemical synthesis under ultrasonic irradiation. Then the poly(styrene‐alt‐maleic anhydride) (PSMA) was synthesized by free radical polymerization. Moreover, the PANI was grafted on the PSMA backbone to prepare a comb‐like conductive copolymer for improving its processability as a new method. The products were characterized by Fourier transform infrared, ultraviolet–visible spectroscopy and X‐ray diffraction patterns. Morphology of the samples was also investigated by scanning electron microscopy images. Finally, the solubility and conductivity of the products were studied, and it resulted in high solubility of the products in water and other common organic solvents in comparison to the pure PANI. Copyright © 2015 John Wiley & Sons, Ltd.