Electrolyte Effects on Charge Transport Behavior of [Os(bpy)2(PVP)10Cl]Cl and [Ru(bpy)2(PVP)10Cl]Cl Redox Polymers in Ultra‐Thin Films of Polyions

Metallopolymer films have important applications in electrochemical catalysis. The alternate electrostatic layer‐by‐layer method was used to assemble films of [Ru(bpy)₂(PVP)₁₀Cl]Cl (denoted as ClRu‐PVP) and [Os(bpy)₂(PVP)₁₀Cl]Cl (ClOs‐PVP) metallopolymers onto pyrolytic graphite electrodes. Film thickness estimated by quartz crystal microbalance was 6–8 nm. The effects of pH, electrolyte species and concentration on the electrochemical properties of these electroactive polymers were studied using cyclic voltammetry (CV). Behavior in various electrolytes was compared. Also the mass changes within the ultra‐thin film during redox of Os^2+/3+ were characterized by in situ electrochemical quartz crystal microbalance (EQCM). The results indicate rapid reversible electron transfer, and show that both ClRu‐PVP and ClOs‐PVP have compact surface structures while ClOs‐PVP is a little denser than ClRu‐PVP. Although hydrogen ions do not participate in the chemical reaction of either film, the movement of Na⁺ cation and water accompanies the redox process of ClOs‐PVP films.     

Fading Spectrophotometric Method for the Determination of Polyvinylpyrrolidone with Eosin Y

在弱酸性HC1-NaAc缓冲介质中,曙红Y（EY）在可见光区有强烈的光吸收,其最大吸收波长(lmax)位于517 nm处,而聚乙烯吡咯烷酮(PVP)在250-700 nm之间无光吸收,当EY与PVP反应形成结合产物时,EY发生明显的褪色作用,最大褪色波长仍位于517 nm,并在545 nm处出现一个较小的吸收峰。其褪色程度（DA）与PVP浓度在0.40~3.20 µg mL-1范围成线性关系,此褪色反应的灵敏度高,摩尔吸光系数(ε)是6.4 × 106 L mol-1 cm-1,对PVP的检出限为0.12 µg mL-1。并研究了反应的影响因素,结果表明方法具有较好的选择性,据此发展了一种曙红Y褪色分光光度法测定PVP的新方法。方法简便快速,可用于啤酒中PVP的定量测定。     

Preparation of Polymer Nanofibers Containing Silver Nanoparticles by Using Poly(N‐vinylpyrrolidone)

Summary: Poly(N‐vinylpyrrolidone) (PVP) was used in two methods to prepare polymer nanofibers containing Ag nanoparticles. The first method involved electrospinning the PVP nanofibers containing Ag nanoparticles directly from the PVP solutions containing the Ag nanoparticles. N,N‐Dimethylformamide was used as a solvent for the PVP as well as a reducing agent for the Ag⁺ ions in the PVP solutions. In the second method, poly(vinyl alcohol) (PVA) aqueous solutions were electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles. The Ag nanoparticles were evenly distributed in the PVA nanofibers. PVP containing Ag nanoparticles could be used to introduce Ag nanoparticles to other polymer nanofibers that are miscible with PVP.

TEM image of a PVA nanofiber electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles.     

Characterization of blends of poly(vinyl chloride) and poly(N‐vinyl pyrrolidone) by FTIR and 13C CP/MAS NMR spectroscopy

Blends of poly(vinyl chloride) (PVC) with Poly(N‐vinyl pyrrolidone) (PVP) were investigated by Fourier infrared spectroscopy (FTIR) and high‐resolution solid‐state ¹³C cross‐polarization/magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy. The intermolecular interactions between PVP and PVC are weaker than the self‐association of PVP and the inclusion of the miscible PVC results in the decreased self‐association of PVP chains, which was evidenced by the observation of high‐frequency shift of amide stretching vibration bands of PVP with inclusion of PVC. This result was further substantiated by the study of ¹³C CP/MAS spectra, in which the chemical shift of carbonyl resonance of PVP was observed to shift to a high field with inclusion of PVC, indicating that the magnetic shielding of the carbonyl carbon nucleus is increased. The proton spin‐lattice relaxation time in the laboratory frame (T₁ (H)) and the proton spin‐lattice relaxation time in the rotating frame (T_1ρ(H)) were measured as a function of the blend composition to give the information about phase structure. It is concluded that the PVC and PVP chains are intimately mixed on the scale of 20–30Å. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2412–2419, 1999     

Molecular modeling simulation and experimental measurements to characterize chitosan and poly(vinyl pyrrolidone) blend interactions

Blends of chitosan and poly(vinyl pyrrolidone) (PVP) have a high potential for use in various biomedical applications and in advanced drug‐delivery systems. Recently, the physical and chemical properties of these blends have been extensively characterized. However, the molecular interaction between these two polymers is not fully understood. In this study, the intermolecular interaction between chitosan and PVP was experimentally investigated using ¹³C cross‐polarization magic angle‐spinning nuclear magnetic resonance (¹³C CP/MAS NMR) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). According to these experimental results, the interaction between the polymers takes place through the carbonyl group of PVP and either the OH? C₆, OH? C₃, or NH? C₂ of chitosan. In an attempt to identify the interacting groups of these polymers, molecular modeling simulation was performed. Molecular simulation was able to clarify that the hydrogen atom of OH? C₆ of chitosan was the most favorable site to form hydrogen bonding with the oxygen atom of C?O of PVP, followed by that of OH? C₃, whereas that of NH? C₂ was the weakest proton donor group. The nitrogen atom of PVP was not involved in the intermolecular interaction between these polymers. Furthermore, the interactions between these polymers are higher when PVP concentrations are lower, and interactions decrease with increasing amounts of PVP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1258–1264, 2008     

Phase Evolution of Cu?S System in Ethylene Glycol Solution: the Effect of Anion and PVP on the Transformation of Thiourea

The transformation mechanisms of thiourea in ethylene glycol solution was systematically investigated in this report, which shows the transformation process is influenced by the anion (NO^3?, Cl^?, Br^?) and polyvinylpyrrolidone (PVP). Thiourea (tu) isomerizes into ammonium thiocyanate when NO^3? is present, regardless of the existence of PVP. For Cl^?, thiourea coordinates with copper anion to form [Cu(tu)]Cl·1/2H₂O complex whether PVP is present. When it comes to Br^?, thiourea hydrolyzes in the cooperation of PVP or coordinates with copper anion to form [Cu(tu)Br]·1/2H₂O complex without PVP. The different transformation routes will lead to different phase evolution of the Cu? S system. This work may provide a new understanding of the transformation of thiourea in ethylene glycol solution. The optical properties of the as‐prepared copper sulfides exhibit signi?cant stoichiometry‐dependent features which may have potential applications in semiconductor photovoltaic devices.     

Interactions between metal chlorides and poly(vinyl pyrrolidone) in concentrated solutionsand solid‐state films

The rheological behavior of poly(vinyl pyrrolidone) (PVP)/N,N‐dimethylformamide (DMF) solutions containing metal chlorides (LiCl, CaCl₂, and CoCl₂) were investigated, and the results showed that the nature of the metal ions and their concentration had an obvious effect on the steady‐state rheological behavior of PVP–DMF solutions with different molecular weights. The apparent viscosity of the PVP–DMF solutions increased with an increasing metal‐ion concentration, and the viscosity increment was dependent on the metal‐ion variety_. For a CaCl₂‐containing PVP–DMF solution, for example, the critical shear rate at the onset of shear thinning became smaller with increasing CaCl₂ concentration. It was believed that multiple interactions among metal ions, carbonyl groups of PVP, and amide groups in DMF determined the solution properties of these complex fluids; therefore, ¹³C NMR spectroscopy was used to detect the interactions in systems of PVP–CaCl₂–DMF and PVP–LiCl–DMF solutions. NMR data showed that there were obvious interactions between the metal ions and the carbonyl groups of the PVP segments in the DMF solutions. Furthermore, IR spectra of the PVP/metal chloride composites demonstrated that the interaction between the metal ions and carbonyl groups in the PVP unit occurred and that the PVP chain underwent conformational variations with the metal‐ion concentration. DSC results indicated that the glass transition temperatures of the PVP/metal chloride composites increased with the addition of metal ions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1589–1598, 2007     

聚乙烯醇/聚乙烯吡咯烷酮碱性复合膜的制备及其性能

通过在不同浓度KOH溶液中进行掺杂,制备出了聚乙烯醇/聚乙烯吡咯烷酮(PVA/PVP)碱性聚合物电解质膜.详尽考察了膜的组成、微观结构、热稳定性、离子电导率和甲醇吸收率.结果表明,PVA与PVP两者具有较好的相容性,当m(PVA)∶m(PVP)=1∶0.5时,膜断面致密、均匀,未发生大尺度相分离.PVP的混入可以极大提高复合膜的电导率和热稳定性.当m(PVA)∶m(PVP)=1∶1时,复合膜的电导率可达2.01×10-3 S.cm-1.PVA/PVP/KOH膜的甲醇吸收率随温度的升高没有明显变化,100℃时其甲醇吸收率仅为同条件下Nafion 115膜的1/4.这表明该复合膜有望作为一种新型的碱性直接甲醇燃料电池用固体电解质膜且可提高膜的使用温度.     

DNA Separation by Microchip Electrophoresis Using Copolymers of Poly(vinylpyrrolidone) and Hydroxyethylcellulose

Copolymers of poly(vinylpyrrolidone) (PVP) and hydroxyethylcellulose (HEC) were synthesized, with PVP to HEC molar ratios of 3:1, 2:1 and 1:1. The copolymers were tested as separation media in DNA fragment separation analysis by microchip electrophoresis (MCE). Separation efficiency over 3.8×10⁵ for 118 bp has been reached by using the bare channels without the additional polymer coating step. Under optimized separation conditions for longer read length DNA sequencing, the separation ability of the copolymers decreased with decreasing (PVP‐co‐HEC) molar ratio from 3:1 to 2:1 and 1:1. In comparison with (PVP‐co‐HEC) 1:1, the copolymer with (PVP‐co‐HEC) 3:1 ratio showed high separation efficiency. By using a 20 g·L^?1 copolymer with (PVP‐co‐HEC) 3:1 ratio, ΦΧ174‐HaeIII digest DNA marker was successfully separated within 3 min.     

Chainlength effects on interactions of polyvinylpyrrolidone with low and high molecular compounds

Very narrow fractions of polyvinylpyrrolidone (PVP) for a range of low molecular weight from 20·10³ to $\text{\&{;10}{}^3$ were prepared by gel filtration using sephadex gel. Interactions between fractions of different M_n and small molecules (iodine and 1-anilinonaphthaline-8-sulphonate) and polymers (polymethacrylic and polyacrylic acids) were studied in aqueous solution. The ability of PVP to form complexes with low molecular weight compounds depends on chainlength. The greatest loss of the ability was observed for PVP with M_n on passing from 5·10³ to $\text{\&{;10}{}^3$. The chainlength effects for PVP are accounted for an unlike dehydration and unlike “local” link concentration near links for these macromolecules in water. For PAA and PMAA. the threshold values of M?_n, below which there is the beginning of weakening of complexation for PVP, are 6·10³ and 2.5·10³ respectively. The difference of the complex formation for these polyacids appears to be related to hydrophobic interactions between the χ-methyl groups of PMAA and nonpolar regions of PVP.     

Synthesis and characterization of pH‐sensitive PAMPS/PVP nanogels in aqueous media

A novel method for preparing poly (2‐acrylamido‐2‐methylpropane sulfonic acid) (PAMPS) and poly (vinylpyrrolidone) (PVP) complex nanogels in PVP aqueous solution is discussed in this paper. The PAMPS/PVP complex nanogels were prepared via polymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) monomer in the presence of PVP nanoparticles which formed in water/acetone cosolvent in presence of N, N′‐methylenebisacrylamide (MBA) as a crosslinker, N, N, N′, N′‐tetramethylethylenediamine (TEMED) and potassium peroxydisulfate (KPS) as redox initiator system. The results of FTIR and ¹H NMR spectra indicated that the compositions of PAMPS/PVP are consistent with the designed structure. TEM micrographs proved that PAMPS/PVP nanogels possess the spherical morphology before and after swelling. These PAMPS/PVP nanogels exhibited pH‐induced phase transition due to protonation of PAMPS chains. The properties of PAMPS/PVP nanogels indicate that PAMPS/PVP nanogels can be developed into a pH‐controlled drug delivery system. Copyright © 2009 John Wiley & Sons, Ltd.     

Fabrication of CdS Nanorods in PVP Fiber Matrices by Electrospinning

Summary: A controlled fabrication of rod‐like nanostructures of cadmium sulfide (CdS) incorporated into polymer fiber matrices has been developed by an electrospinning method. Here, poly(vinyl pyrrolidone) (PVP) was used as a polymer capping reagent, utilizing the interactions of cadmium ions with the carbonyl groups in the PVP molecules. The formation of CdS nanorods inside the PVP was carried out via the reaction of Cd²⁺ with H₂S. SEM images showed that the electrospun films of PVP/CdS are composed of fibers with a diameter between 100 and 900 nm. TEM proved that most of the CdS nanorods are incorporated in the PVP fibrous film. The diameter of the rod is about 50 nm and the length is from 100 to 300 nm.

TEM image of the CdS nanorods formed in the PVP fibrous film.     

In-situ fabrication of barium titanate@polyvinyl pyrrolidone in polyvinylidene fluoride polymer nanocomposites for dielectric capacitor applications

We have demonstrated an in situ route to design barium titanate (BT)@polyvinyl pyrrolidone (PVP) nanoparticles (NPs) in PVP/polyvinylidene fluoride (PVDF) blends. Thus, the PVP simultaneously acted as a linker and a part of the polymer matrix. We have hydrothermally synthesized the tetragonal phase of BT NPs (~150 nm). The BT NPs content was varied from 0 to 15 vol%. The resulting polymer nanocomposites generated enormous interfaces because of homogeneously dispersed BT@PVP NPs. Furthermore, the PVP simultaneously tailored the interfacial properties surrounding the BT NPs and bulk of the polymer matrix. Therefore, we achieved an enhanced maximum polarization (P_max) and energy density (U_d) of 27.9 μC cm⁻² and 13.4 J cm⁻³ (2261 kV cm⁻¹), respectively, at 7.5 vol% BT NPs loadings. At the same time, PVP/PVDF blends showed P_max and U_d of only 3.9 μC cm⁻² and 4.6 J cm⁻³ (3369 kV cm⁻¹), respectively. This simple approach of in situ nanomaterials modification will lead to development of low-cost and time-efficient dielectric capacitors.     

Ion-free latex films composed of fused polybutadiene and poly (vinyl pyrrolidone) particles as polymer electrolyte materials

Latex films composed of fused polybutadiene (PB) and poly (vinyl pyrrolidone) (PVP) particles that contain no ionic, hydroxyl, or amino groups were swelled with lithium salt solutions to yield new polymer electrolyte materials. The latex particle consists of a nonpolar, rubbery core that contains the PB component and a polar, glassy shell that contains the PVP component. The particle core-shell morphology was retained in the solid state, after the latex dispersion medium was removed and the films dried at high temperatures, due to the high T_g of the PVP shell. The films swelled when immersed in lithium salt solutions, and ionic conductivity of swollen films was greater than 10^-3 S/cm. Swelling and ionic conduction occurred only in the polar PVP component. Extraction of PVP occurred with extended swelling. © 1994 John Wiley & Sons, Inc.     

Preparation of poly(vinylpyrrolidone)-protected Prussian blue nanoparticles-modified electrode and its electrocatalytic reduction for hemoglobin

In this paper, a novel modified electrode was developed by using highly dispersed Prussian blue (PB) nanoparticles protected by poly(vinylpyrrolidone) (PVP). The size of the nanoparticles was controlled through adjusting the feed ratio of PVP/Fe²⁺. Physical characteristics of the nanocomposite were studied by transmission electron microscopy (TEM), UV-vis, IR spectroscopy, and X-ray powder diffraction (XRPD) analysis. The electrocatalytic reduction of hemoglobin (Hb) at PVP-protected PB nanoparticles (PVP/PB NPs)-modified electrode had been investigated. In addition, the size effects and biocompatibility of PVP/PB NPs for the electrochemistry of Hb were also observed. Experimental results indicated that the reduction peak currents of Hb were linear with its concentrations over the range from 1.0 × 10⁻⁷ to 1.2 × 10⁻⁵ mol/L and the calculated detection limit (S/N = 3) was 4.0 × 10⁻⁸ mol/L.     

The mechanism of ascorbic acid oxidation by Cu(II)-poly-4-vinylpyridine complexes

The mechanism of ascorbic acid (DH₂) oxidation with molecular oxygen catalysed by the polynuclear complex of Cu²⁺ with poly-4-vinylpyridine (PVP), partially quaternized by dimethylsulphate, has been studied. The half-conversion time of the reaction of DH₂ with Cu(II) PVP under anaerobic conditions is independent of [Cu²⁺]. At pH 3.5, t_0.5 (sec) = 0.8 + 5 × 10^?4 [DH₂]. The formation of an intermediate cupric-ascorbate complex is suggested (K_c ≈ 10⁴ M^?1). Free radicals of ascorbic acid are detected by the ESR-method combined with a flow technique. The small steady-state concentration of radicals indicates that their decay occurs inside the macromolecular complex. The rate constant of the PVP Cu(II) DH^? ternary complex dissociation is ≈0.4 sec^?1 (pH 3.5). The reaction of Cu(I) PVP with O₂ is not accompanied by formation of O₂^? outside the macromolecule bulk. The rate constant of this reaction is 1.3 ± 0.15) × 10² M^?1 sec^?1 (pH 3.5). The cyclic mechanism of the catalytic reaction is suggested to include interchange of the redox state of copper-ions. About $\text{2}\text{3}$ of the total copper ion exists in the form Cu(I) PVP during the reaction at pH 3.5. The rate of DH₂ oxidation under these conditions is limited by the rate of Cu(I) PVP reaction with O₂. At pH 4.5 the overall reaction rate is limited by the rate of interaction of Cu(II) PVP with DH^?.     

Polyetherimide/polyvinylpyrrolidone vapor permeation membranes. Physical and chemical characterization

Integrally skinned capillary tube membranes were prepared by the wet-phase inversion method. A series of polyetherimide (PEI, Ultem 1000) membranes were prepared with varying amounts of polyvinylpyrrolidone (PVP) in the casting solution. The surfaces of the membranes were analyzed by electron spectroscopy for chemical analysis (ESCA). It was found that the molecular structure of PEI, both with and without PVP, changes considerably during membrane preparation. The ESCA results indicated that the amount of PEI nitrogen remaining fully imidized at the surface varied in the range 63–86%. The PVP/PEI mass ratio at the membrane surface was found to increase linearly from 0 to 0.10 as the ratio was increased from 0 to 0.43 in the casting solution. The PVP/PEI mass ratio in the membrane bulk was determined by thermogravimetric analysis (TGA) to reach a maximum of 0.067. Vapor permeation experiments were done with a water/n-propanol mixture. The addition of PVP increased the membrane selectivity (α=P_A/P_B, A=water, B=1-propanol) from 76 to 810, while the permeance for water remained relatively constant at 1.3×10⁻⁶ mol/m² s Pa.     

Simultaneous Electrochemical Determination of Hydroquinone and Bisphenol A using a Carbon Paste Electrode Modified with Silver Nanoparticles

In this paper, a rapid and sensitive modified electrode for the simultaneous determination of hydroquinone (HQ) and bisphenol A (BPA) is proposed. The simultaneous determination of these two compounds is extremely important since they can coexist in the same sample and are very harmful to plants, animals and the environment in general. A carbon paste electrode (CPE) was modified with silver nanoparticles (nAg) and polyvinylpyrrolidone (PVP). The PVP was used as a reducing and stabilizing agent of nAg from silver nitrate in aqueous media. The nAg‐PVP composite obtained was characterized by transmission electron microscopy and UV‐vis spectroscopy. The electrochemical behavior of HQ and BPA at the nAg‐PVP/CPE was investigated in 0.1 mol L⁻¹ B−R buffer (pH 6.0) using cyclic voltammetry (CV) and square wave voltammetry (SWV). The results indicate that the electrochemical responses are improved significantly with the use of the modified electrode. The calibration curves obtained by SWV, under the optimized conditions, showed linear ranges of 0.09–2.00 μmol L⁻¹ for HQ (limit of detection 0.088 μmol L⁻¹) and 0.04–1.00 μmol L⁻¹ for BPA (limit of detection 0.025 μmol L⁻¹). The modified electrode was successfully applied in the analysis of water samples and the results were comparable to those obtained using UV‐vis spectroscopy.     

Synthesis and gas permeation properties of poly(vinyl chloride)‐graft‐poly(vinyl pyrrolidone) membranes

A series of amphiphilic graft copolymers consisting of poly(vinyl chloride) (PVC) main chains and poly(vinyl pyrrolidone) (PVP) side chains, i.e. PVC‐g‐PVP, was synthesized via atom transfer radical polymerization (ATRP), as confirmed by ¹H NMR, FT‐IR spectroscopy, and gel permeation chromatography (GPC). Transmission electron microscope (TEM) and small angle X‐ray scattering (SAXS) analysis revealed the microphase‐separated structure of PVC‐g‐PVP and the domain spacing increased from 21.4 to 23.9 nm with increasing grafting degree. All the membranes exhibited completely amorphous structure and high Young's modulus and tensile strength, as revealed by wide angle X‐ray scattering (WAXS) and universal testing machine (UTM). Permeation experimental results using a CO₂/N₂ (50/50) mixture indicated that as an amount of PVP in a copolymer increased, CO₂ permeability increased without the sacrifice of selectivity. For example, the CO₂ permeability of PVC‐g‐PVP with 36 wt% of PVP at 35°C was about four times higher than that of the pristine PVC membrane. This improvement resulted from the increase of diffusivity due to the disruption of chain packing in PVC by the grafting of PVP, as confirmed by WAXS analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

Spectroscopic and Discharge Studies on Graphene Oxide Doped PVA/PVP Blend Nanocomposite Polymer Films

Graphene oxide (GO) nanoparticles were synthesized by modified Hummers method. The synthesized GO nanoparticles were incorporated in polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) blend polymers for the preparation of nanocomposite polymer films by solution cast technique. Different characterizations such as XRD, UV–Vis and FTIR were carried-out on to the prepared nanocomposite polymer films. The thermal analysis of the films was studied by DSC. The morphology of PVA/PVP:GO polymer films confirms GO was exfoliated within the PVA/PVP matrix and also reveals the heterogeneous phase of nanocomposite polymer electrolyte systems. From the conductivity studies the highest conductivity of PVA/PVP: GO (0.45: 0.3) was found to be 8.05 × 10^–4 S/cm at room temperature. Solid state battery has been fabricated with the configuration of Mg⁺/(PVA/PVP:GO)/(I₂ + C + electrolyte) and its cell parameters were calculated for a constant load of 100 kΩ.