Poly(o-phenylenediamine)/MWNTs composite film as a hole conductor in solid-state dye-sensitized solar cells

All solid-state dye-sensitized solar cells were fabricated using in situ electrochemically polymerized poly(o-phenylenediamine)/MWNTs (PoPD/MWNTs) as a hole transport materiel. The electrochemical behaviors of PoPD/MWNTs indicated that the electron exchange efficiency improves obviously of PoPD after the addition of carbon nanotubes. The PoPD/MWNTs composite film was deposited on the dye anchored porous TiO₂ electrode and I–V characterization was performed under simulated AM 1.5 illumination. Fabricated devices for the PoPD/MWNT composites prepared in 0.1 g/L MWNTs showed a photoresponse with an open-circuit voltage V_OC of 479 mV and a short-circuit current density (I_SC) of 0.572 mA/cm² with the overall conversion efficiency of 0.13%, higher than those of the cell with only PoPD (i.e., I_SC = 0.275 mA/cm², V_OC = 462 mV, FF = 0.35, η = 0.04%). It is obvious that the introduction of MWNTs to PoPD composites could improve the cell performance.     

A study on optical limiting properties of Eosin-Y and Eriochrome Black-T dye-doped poly (vinyl alcohol) composite film

A poly (vinyl alcohol) PVA/Eriochrome Black-T (EBT) dye, and PVA/Eosin-Y (EY) dye composite film was prepared using a solution casting process. The dye-doped composite polymer films were characterized by UV–vis spectroscopy. An optical band gap (E_g) of pure PVA reduced from 4.22?eV to 2.80?eV for PVA/EBT film and 2.14?eV for PVA/EY film respectively. This result indicates the occurrence of inter-molecular hydrogen bonding between the –OH functional group in PVA chains and sulfonate (EBT) and carboxyl group (EY) in dye molecules, respectively. Moreover, the experimental result of PVA/EBT and PVA/EY composite film showed the excellent properties of a large scale cut-off filter in the ultraviolet and visible range region.     

Sensitive amperometric pyridoxine sensor based on self‐assembled Prussian blue nanoparticle‐modified poly(o‐phenylenediamine)/glassy carbon electrode

Prussian blue nanoparticles (PBNPs) were prepared by a self‐assembly process on a glassy carbon electrode (GCE) modified with poly(o‐phenylenediamine) (PoPD) film. The stepwise fabrication process of PBNP‐modified PoPD/GCE was characterized using scanning electron microscopy and electrochemical impedance spectroscopy. The prepared PBNPs showed an average size of 70 nm and a homogeneous distribution on the surface of the modified electrode. The PBNPs/PoPD/GCE showed electrocatalytic activity towards the oxidation of pyridoxine (PN) and was used as an amperometric sensor. The modified electrode exhibited a linear response for PN oxidation over the concentration range 3–38.5 μM with a detection limit of ca 6.10 × 10^?7 M (S/N = 3) and sensitivity of 2.79936 × 10³ mA M^?1 cm^?2 using an amperometric method. The mechanism and kinetics of the catalytic oxidation reaction of PN were investigated using cyclic voltammetry and chronoamperometry. The values of α, k_cat and D were estimated as 0.36, 1.089 × 10² M^?1 s^?1 and 8.9 × 10^?5 cm² s^?1, respectively. This sensor also exhibited good anti‐interference and selectivity. Copyright © 2016 John Wiley & Sons, Ltd.     

Immobilization of urease in poly(1-vinyl imidazole)/poly(acrylic acid) network

In this study, urease was immobilized in a polymer network obtained by complexation of poly(1-vinyl imidazole) (PVI) with poly(acrylic acid) (PAA). Preparation of the polymer network was monitored by FT-IR spectroscopy. Scanning electron microscopy (SEM) revealed that enzyme immobilization had a strong effect on film morphology. Proton conductivity of the PVI/PAA network was measured via impedance spectroscopy under humidified conditions. Values of the Michaelis-Menten constant (K _M) for immobilized urease were higher than for the free enzyme, indicating a decreased affinity of the enzyme to its substrate. The basic characteristics (pH_opt, pH_stability, T _opt, T _stability, reusability, and storage stability) of immobilized urease were determined. The results show that the PAA/PVI polymer network is suitable for enzyme immobilization.     

Electrochemical Impedance Spectra of Poly(3-octylthiophene) Films

Charge transfer in poly(3-octylthiophene) films in 0.05–0.5 M LiClO₄ solutions in acetonitrile is studied by an electrochemical impedance method. The resistance to charge transfer R _ct and the capacitance of the electrical double layer C _dl are calculated from the high-frequency semicircle and referred to the film/electrolyte interface. The low-frequency capacitance C _lf and effective diffusion coefficient D _ef are determined by analyzing the region of medium and low frequencies. The discrepancies between potential dependences of C _lf and D _ef derived experimentally and calculated within a simple model for a redox film are analyzed. The assumption is made that additional factors, such as a macroporous character of the films and the change in their properties during oxidation, which results from the film swelling, the change in the film volume and the solvation character, should be taken into account.     

Cobalt ion-doped polyaniline,poly(N-methylaniline), and poly(N-ethylaniline): electrosynthesis and characterisation using electrochemical methods in acidic solutions

Cobalt ion (Co²⁺)-doped polyaniline (PANI-Co), poly(N-methylaniline) (PNMA-Co), and poly(N-ethylaniline) (PNEA-Co) films were synthesised electrochemically on a pencil graphite electrode (PGE) and their electrochemical properties were investigated for supercapacitor applications. The polymer film-coated electrodes (PGE/PANI-Co, PGE/PNMA-Co, and PGE/PNEA-Co) thus obtained were characterised by scanning electron microscopy (SEM) and different electrochemical methods. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were employed in 0.1 M H₂SO₄ solution to calculate the specific capacitance (C _S) values of the electrodes. The maximum C _S of 192.94 F g^?1, 139.83 F g^?1, and 47.12 F g^?1 were achieved for PGE/PANI-Co, PGE/PNMA-Co, and PGE/PNEA-Co at 1 mV s^?1, respectively. On the other hand, the charge/discharge stability of the electrodes was analysed using the repeating chronopotentiometry (RCP) method. The RCP measurements indicate that the electrodes could be used as an electrode active material for low voltage supercapacitor applications.     

Electrocatalytic oxidation of methanol on carbon ceramic electrode modified by platinum nanoparticles incorporated in poly (o-phenylenediamine) film

Carbon ceramic electrode, a new electrode substrate, was prepared by sol–gel procedure and used for the electropolymerization of o-phenylenediamine and incorporation of platinum nanoparticles into the resulting poly(o-phenylenediamine) (PoPD) film. The modified electrode was used for electrooxidation of methanol in 0.3 M H₂SO₄ as supporting electrolyte. The presence of PoPD film increased considerably the efficiency of deposited Pt nanoparticles toward the electrocatalytic oxidation of methanol. The effective parameters on the electrooxidation of methanol, i.e., amounts of polymer and Pt catalyst, medium temperature, working potential limit in anodic direction, and potential scan rate, were investigated, and the results were discussed.     

Growth of poly(3,4‐ethylenedioxythiophene) films prepared by base‐inhibited vapor phase polymerization

Transparent [90% transmittance at 550 nm at a sheet resistance (R_s) of 279 Ω sq^?1] poly(3,4‐ethylenedioxythiophene) (PEDOT) films with electrical conductivities up to 1354 S cm^?1 are prepared using base‐inhibited vapor phase polymerization at atmospheric pressure. The influence of reaction conditions, such as temperature and growth time, on the film formation is investigated. A simple and convenient two‐electrode method is used for the in situ measurement of resistance, enabling to investigate the growth mechanism of polymer films and the influence of different parameters (relative humidity and the amount of oxidant) on the film growth. Low humidity exerts a detrimental effect on film growth and conductivity. In situ R_s measurements suggest that a large structural change occurs upon washing the PEDOT‐oxidant film. © 2014 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2014 , 52, 561–571     

Preparation of poly(biphenylene vinylene) type polymers by Ni‐promoted polycondensation and their basic optical properties

Ni(0)‐complex promoted dehalogenation polymerization of 1,2‐bis(4‐bromophenyl)ethylene derivatives gave poly(p‐biphenylene vinylene) type polymers, [—C₆H₂R—CR² = CR²—C₆H₂R—)_n (P(R¹,H) and P(H,R²) ], having substituents (R¹ = Me, Et, CHMe₂, and n‐C₈H₁₇, R² = Me, Et, n‐C₆H₁₃, n‐C₁₁H₂₃, and Ph) at the benzene ring or vinylene group in 90–99% yields. The polymers were soluble in organic solvents such as CHCl₃, dimethylformamide, and tetrahydrofuran, and gave M_n of 2.4–5.3 × 10³ in gel permeation chromatography analysis. The absorption peak of the polymers appeared at a longer wavelength than that of the corresponding monomers by about 30 nm due to the expansion of the π‐conjugation system. The polymers were photoluminescent in solutions and in their films, emitting blue or green light. P(R¹,H)s gave higher quantum yields (Φ = 0.35–0.51) than P(H,R²) s in CHCl₃. P(H,R²) s showed a large Stokes shift (9600–13,500 cm⁻¹) in their photoluminescence. Single‐layer and multilayer light emitting diodes using vacuum deposited thin film of P(H,Ph) were prepared. Polymers with long alkyl substituents formed an ordered structure in the solid state as judged from their XRD patterns. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1493–1504, 2000     

Miscibility and thermal stability of poly(vinyl alcohol)/chitosan mixtures

The miscibility and the thermal behaviour of chitosan acetate (ChA) with poly(vinyl alcohol) (PVA) have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Chitosan is blended with poly(vinyl alcohol) in acetic acid solution and this solution is cast to prepare the blend film. From thermal curves the thermal transitions: T_g, T_m and characteristic temperatures of decomposition: T_di, T_max have been determined and compared. The influence of the degree of PVA hydrolysis on the thermal properties of blend systems has been discussed.Based upon the observation on the DSC analysis, the melting point of PVA is decreased when the amount of ChA in the blend film is increased. Though some broadening of the transition curves could be noticed (DSC, TGA and DMA), the obtained results suggest that in the solid ChA/PVA blends the components are poorly miscible. Only PVA sample with relatively low DH = 88% and hence low degree of crystallinity shows partial miscibility with ChA of relatively low molecular weight.     

Synthesis and physico-chemical studies of some polynuclear mixed carboxylate complexes of nickel(II)

A number of polynuclear mixed carboxylates of nickel(II) with the general composition [Ni(OOCCH₃)_2–n (OOCR) _n ] _x (whereR=C₁₃H₂₇, C₁₅H₃₁, C₁₇H₃₅ and C₂₁H₄₃ andn=1 or 2) have been synthesized by the transacylation reactions of anhydrous nickel acetate with higher carboxylic acids in refluxing toluene. On recrystallization from benzene-alcohol mixtures, mono-alcoholate complexes, Ni(OOCCH₃)_2–n (OOCR) _n ·ROH (whereR=CH₃ and C₂H₅) have been isolated. All these derivatives have been characterized by the molecular weight determinations, infra-red and electronic reflectance spectra and magnetic susceptibility measurements.

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Synthese und Eigenschaften einiger gemischter Carboxylat-Komplexe von Nickel(II)

Zusammenfassung Komplexe des Typs [Ni(OOCCH₃)_2–n (OOCR) _n ] _x (mitR=C₁₃H₂₇, C₁₅H₃₁, C₁₇H₃₅ und C₂₁H₄₃,n=1 oder 2) wurden aus wasserfreiem Nickelacetat mit höheren Carbonsäuren in siedendem Toluol erhalten. Bei der Kristallisation aus Benzol-Alkohol-Mischungen wurden Monoalkoholate Ni(OOCCH₃)_2–n (OOCR) _n ·ROH (mitR=CH₃ und C₂H₅) isoliert. Die Charakterisierung der Komplexe erfolgte mittels Molekulargewichtsbestimmung, Infrarot- und Elektronenspektren und der Messung der magnetischen Susceptibilität.

     

Viscoelastic behaviors and molecular motions of highly syndiotactic poly(vinyl alcohol) fibers

The viscoelastic behavior and molecular motion of highly syndiotactic poly(vinyl alcohol) (S‐PVA) fibers with a dyad syndiotacticity (r) of 69% were studied by dynamic mechanical thermal analysis and wide‐angle X‐ray diffraction and compared with those of atactic poly(vinyl alcohol) (A‐PVA) fibers with r = 54%. The β_c dispersion, based on the molecular motion of the chain molecules in the crystalline regions, was observed for A‐PVA around 120–140 °C, and the only primary (α_c) dispersion was observed for S‐PVA around 180 °C. The thermal expansion coefficients for the a and c axes of the A‐PVA crystal changed discontinuously around 120 °C, which corresponded to the β_c dispersion. For S‐PVA, the coefficient for the (002) plane changed discontinuously around 100 °C, similarly to A‐PVA, but that for the (100) plane remained unchanged between 20 and 220 °C. These results showed that the intermolecular hydrogen bonding of S‐PVA was stronger in the direction of the a axis than in the other directions, suppressing the β_c dispersion. The storage modulus and thermal expansion coefficient of the (020) plane (molecular axis) of S‐PVA decreased markedly around 180 °C, and this indicated that the α_c dispersion was due to the torsional motion of the molecular chains in the crystalline regions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 800–808, 2004     

Structure–property relationships of poly(vinyl alcohol). II. The influence of molecular regularity on the crystallization–dissolution temperature relationships of poly(vinyl alcohol)

Dissolution temperatures T_s have been determined for poly(vinyl alcohol) (PVA) samples of varying tacticity as a function of crystallization temperatures T_c. From the values of T_s and T_c, one can obtain values of (T_m)_∞, the dissolution temperature of crystals of infinite stepheight. (T_m)_∞ is a characteristic property of a given sample. This method of characterization is very sensitive and reliable for detecting differences in molecular regularity among PVA samples. The variation of (T_m)_∞ with stereoregularity is attributed in part to differences in hydrogen-bonding characteristics. Determinations of the crystallinities of solution-crystallized PVA have shown that stereoregularity in PVA does not result in higher crystallizability.     

Fabrication of poly(vinyl alcohol)‐graphene quantum dots coated with poly(3,4‐ethylenedioxythiophene) for supercapacitor

Conducting nanofiber composed of poly(vinyl alcohol) (PVA), graphene quantum dots (GQDs) and poly(3,4‐ethylenedioxythiophene) (PEDOT) was prepared for symmetrical supercapacitor through electrospinning and electropolymerization techniques. The formation of PVA nanofibers with the addition of GQDs was excellently prepared with the average diameter of 55.66 ± 27 nm. Field emission scanning electron microscopy images revealed that cauliflower‐like structure of PEDOT was successfully coated on PVA‐GQD electrospun nanofibers. PVA‐GQD/PEDOT nanocomposite exhibited the highest specific capacitance of 291.86 F/g compared with PVA/PEDOT (220.73 F/g) and PEDOT (161.48 F/g). PVA‐GQD/PEDOT also demonstrated a high specific energy and specific power of 16.95 and 984.48 W/kg, respectively, at 2.0 A/g current density. PVA‐GQD/PEDOT exhibited the lowest resistance of charge transfer (R_ct) and equivalent series resistance compared with PEDOT and PVA/PEDOT, indicating that the fast ion diffusion between the electrode and electrolyte interface. PVA‐GQD/PEDOT nanocomposite also showed an excellent stability with retention of 98% after 1000 cycles. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 50–58     

Carbon nanotube/metal oxide dispersed poly(ortho‐aminophenol) as a ternary nanocomposite film: Facile electrosynthesis,surface characterization,and electrochemical pseudocapacitive performance

In this work, CNT‐NiCo₂O₄ was first synthesized via a chemical strategy in order to fabricate the ternary nanocomposite of a p‐type conductive polymer. Subsequently, hybrid poly(o‐aminophenol) POAP/CNT‐NiCo₂O₄ ternary composite films were prepared via the electropolymerization of POAP in the presence of CNT‐NiCo₂O₄ to be used in electrochemical storage devices as the active electrode. Electrochemical analyses including galvanostatic charge–discharge experiments, cyclic voltammetry, and electrochemical impedance spectroscopy were conducted to study the system performance. Furthermore, surface analyses were carried out to characterize the POAP/CNT‐NiCo₂O₄ composite film. Novel nanocomposite materials with the merits of extraordinarily high active surface area, ease of fabrication, and superior stability in aqueous electrolytes are presented for use in electrochemical redox capacitors.     

Long branching in poly(vinyl acetate) and poly(vinyl alcohol). III. Kinetic study of the branching reaction in the radical polymerization of vinyl acetate

The branching reaction in the radical polymerization of vinyl acetate was studied kinetically. Branching occurs by polymer transfer as well as terminal double-bond copolymerization. The chain-transfer constants to the main chain (C_p,2) and to the acetoxy methyl group (C_p,1) on the polymer were calculated on the basis of the experimental data described in the preceding paper giving C_p,2 = 3.03 × 10^?4, C_p,1 = 1.27 × 10^?4 at 60°C, and C_p,2 = 2.48 × 10^?4, C_p,1 = 0.52 × 10^?4 at 0°C. Chain transfer to monomer is important with respect to the formation of the terminal double bond. The total values of transfer constants to the α- or β-position in the vinyl group and the acetoxymethyl group in vinyl acetate was determined to be 2.15 × 10^?4 at 60°C. The transfer constant to the acetyl group in the monomer (C_m,1) was also evaluated to be 2.26 × 10^?4 at 60°C from the quantitative determination of the carboxyl terminals in PVA. These facts suggest that the chain-transfer constant to the α- or β-position in the monomer (C_m,2) is nearly equal to zero within experimental error. Copolymerization reactivity parameters of the terminal double bond were also estimated. In conclusion, it has become clear that the formation of nonhydrolyzable branching by the terminal double-bond reaction can be almost neglected, and hence that the long branching in PVA is formed only by the polymer transfer mechanism. On the other hand, a large number of hydrolyzable branches in PVAc are prepared by the terminal double-bond reaction rather than by polymer transfer.     

Investigations by electrochemical quartz crystal impedance system-electrodeposition of silver and polyaniline

An electrochemical quartz crystal impedance system (EQCIS) which allows rapid and simultaneous measurements of admittance spectra of piezoelectric quartz crystal resonance during electrochemical processes was developed by combining an HP 4395A Network/Spectrum/Impedance analyzer with an EG & G M283 potentiostat. Non-linear least square regression analyses of simultaneously acquired conductance and susceptance data were discussed in detail, giving that R_m, C_s, 1/C_m (or L_m) and of as estimation parameters is the best choice among various fitting routines. Equivalent electrical circuit parameters of quartz crystal resonance during electrodeposition of silver and polyaniline and electrochemical processes of the deposits were obtained and discussed according to changes in electrode mass, electrode surface roughness and film conductivity etc. The significant changes of motional resistance R_m and static capacitance C, observed in the silver case was believed to result mainly from changes in electrode surface roughness and the linear relationship between them was well explained by the following equation, C_s = C_q+ C_e = ε_qA_q/ h_q + ε_ek²R_m/[h_e(ωρ_Lη_L]1/2.     

Ion pairing between dissolved poly(o-phenylenediamine) and halogenide ions

An electrically conductive polymer, poly(o-phenylenediamine) (PoPD), is soluble in dimethylsulfoxide (DMSO) without any pretreatment. Cyclic voltammograms of dissolved PoPD were measured in DMSO solutions containing halogenide ions and two reversible redox peak currents were evident. The redox potential shifted with the concentration of the dissolved halogenide ion. The relationship between the potential shift and the concentration determined the relative association constant of PoPD for four halogenide ions: 104 mol⁻¹ dm⁻³ for F⁻; 32 mol⁻¹ dm⁻³ for Cl⁻; 29 mol⁻¹ dm⁻³ for Br⁻ and 9 mol⁻¹ dm⁻³ for I⁻.     

Study of the electrosynthesis of poly(3-butylthiophene) and its semiconductor properties

The mechanism of the electrosynthesis of poly(3-butylthiophene) (PBuT) was studied by cyclic voltammetry and potential step methods in comparison with polybithienyl. The anodic oxidation polymerization of the 3-butylthiophene underwent two steps: oligomer formation and further polymerization to form the polymer. The doping level of the PBuT increases with the cycle number of the potential sweeps during polymerization. The current responses to the potential steps indicate a nucleation and nuclei growth process which is repeated layer to layer. The differential capacity (C _d) and photocurrent were measured at the PBuT films in the aqueous electrolyte solution. The C _d ⁻² vs. E plot shows two regions of linearity, one with a negative slope and the other with a positive slope in different potential regions, which give the same flat-band potential. This indicates that the PBuT film exhibits both p-type and n-type features of a semiconductor at differrent potential regions. The cathodic photocurrent spectrum was analysed by the (j _ph hν)^{2/ n} vs. hν plots, giving band gap energies of 2.41 eV for n=1 and and 2.01 eV for n=4. Received: 29 July 1999 / Accepted: 15 November 1999     

Polyaniline/poly(vinyl alcohol) (PAN/PVA) composite films: the synergy of film structural stiffening, redox amplification, and mobile species compositional dynamics

In this work, we report an unexpected but significant improvement of the redox behavior of conducting polyaniline (PAN) films by trapping intrinsically nonconducting poly(vinyl alcohol) (PVA) in the matrix of the polymer acting as stiffening and/or cross-linking agents. Film structural stiffening of PAN/PVA inclusion was studied in relation to film compositional dynamics. PAN and PAN/PVA composite films were potentiodynamically deposited using high-frequency electrochemical quartz crystal microbalance under electrochemical potentiodynamic control. From the simultaneously obtained measurements of nanogravimetric and cyclic voltammetric data, it has been found that the presence of PVA in the deposition solution increased the rate of PAN film growth as a function of PVA concentration. Characterization of the resultant composite films in monomer-free acidic electrolyte solutions showed significantly enhanced redox behavior of PAN/PVA composite films (with different PVA contents) compared to pure PAN by a factor of ～2–4. For the study of structure–composition relationships of composite polymer films, fluxes of instantaneous mobile species dynamics (ion/solvent) as a function of film redox conversion and potential cycling were correlated with film structural stiffening and the observed unusual redox enhancement of PAN/PVA composite films. Using various experimental timescales, we were able to resolve bound (associated with ion transfer) and free solvent compositional dynamics (associated with thermodynamic activity balance).