Introduction Of Polyvinylpyrrolidone Research Articles

Buckled Amorphous Hollow Carbon Spheres: Facile Fabrication, Buckling Process, and Applications as Electrode Materials for Supercapacitors.

Buckled hollow carbon nanospheres (BHCSs) integrate several attractive properties desired for a variety of potential applications. However, the development of a feasible and simple method for preparing BHCS nanoparticles remains a great challenge. Herein, we present a facile strategy for fabricating monodisperse BHCSs via the compression of intact hollow carbon nanospheres (HCSs) with improved mechanical strength. The essence of our strategy lies in the successful preparation of robust HCSs that can sustain large mechanical deformation during compression, based on the introduction of polyvinylpyrrolidone in the synthesis of HCS templates. Both experiments and finite element analyses are conducted to probe the deformation mechanism of buckling, suggesting that the residual stress introduced by pyrolysis of precursors plays a predominant role in the buckling process. Furthermore, the use of BHCSs as high-performance supercapacitors is demonstrated. Our work provides important insights into the engineering of robust amorphous carbon nanomaterials by the template method and mechanical modulation and provides an innovative synthetic strategy for fabricating asymmetric hollow spheres with potential for a diversity of applications.

The Application of Polyvinylpyrrolidone as a Modifier of Tribological Properties of Lubricating Greases Based on Linseed Oil

The paper presents the research results on the relations between additive content and tribological, rheological, and oxidizing properties of lubricating greases. The greases were based on linseed oil, thickened with amorphous silica Aerosil® and modified with different concentration of polyvinylpyrrolidone. The greases were tested tribologically according to the test on T-02 testing machine and referred to the unmodified control. The evaluation of tribological properties was based on the following parameters: welding load, scuffing load, limiting load of wear, limiting load of scuffing, and limiting pressure of seizure. The results of tribological research revealed the most promising impact of the 3% addition of polyvinylpyrrolidone. All of the crucial parameters were improved in comparison to the unmodified control grease. The spectral analyses revealed that some of the components undergo oxidation during mechanical forces, leading to the formation of the oxidized organic compounds. These substances generated a layer, counteracting the wear of lubricated tribosystem. The improved resistance to oxidation of the tested lubricants with polyvinylpyrrolidone can be explained by the presence of highly hydrophilic pyrrolidone groups and hydrophobic alkyl group in polyvinylpyrrolidone (PVP) molecule. These compounds combine with hydrocarbon chains of linseed oil and act synergistically with the silicon dioxide molecules. The introduction of polyvinylpyrrolidone caused the improvement in dynamic viscosity at lower shear rates and a significant change of viscosity in low temperatures. An increased value of the yield point of the tested lubricating compositions after introduction of the additive was also observed.

Removal of bovine serum albumin from wastewater using fouling resistant ultrafiltration membranes based on the blends of cellulose acetate, and PVP-TiO2 nanoparticles

Fouling resistant ultrafiltration membranes based on the blends of polyvinylpyrrolidone (PVP), TiO2 nanoparticles and cellulose acetate, CA-PVP-TiO2 (CATP), for removal of bovine serum albumin (BSA) were prepared by using phase inversion process. The influences of PVP and TiO2 on the preparation of phase inverted cellulose acetate (CA) ultrafiltration membrane were explored in terms of morphology study, equilibrium water content (EWC), hydraulic resistance, permeability performance, hydrophilicity, and thermal stability. After the introduction of PVP and TiO2 to the ternary (polymer-solvent-non-solvent) system, the formations of finger-like structures and macro-voids were reduced significantly. An improvement in porosity, average pore size, and hydrophilic nature of the CA membranes were detected after the introduction of PVP and TiO2 into the polymer matrix. The interaction between TiO2 and CA was confirmed and the degradation temperature of the CA membrane was significantly improved. BSA protein removal efficiency, anti-fouling performance, and recycling potential of the UF membranes were investigated. The CATP membrane (10.5 wt % CA: 4 wt % PVP: 2 wt % TiO2) has displayed high BSA removal efficiency and flux recovery ratios (NFR) with enhanced anti-fouling performances for the three fouling/rinsing cycles.

PVP-assisted synthesis of unsupported NiMo catalysts with enhanced hydrodesulfurization activity

The effect of polyvinyl pyrrolidone (PVP) on the physicochemical properties and catalytic activities of unsupported NiMo catalysts was studied. The NiMo catalyst precursors were synthesized by a PVP-assisted chemical precipitation method, by adding various contents of PVP to a Ni- and Mo-containing solution. A series of techniques, including CHSN analysis, XRF, XRD, N2 adsorption-desorption, FT-IR, SEM, TG-DSC, TPR, and XPS, were used to characterize the NiMo oxide precursors and sulfided catalysts, and the catalytic activities were tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The characterization results revealed that PVP was efficiently removed due to low contents in the synthesis and high solubility in water. The pore properties and hysteresis loop, the agglomeration of the nanoparticles, and the reducibility of the NiMo precursor were affected by the introduction of PVP, while the phases of the precursors and the thermal stabilities were little changed. Ni3S2 and MoS2 phases were observed in the sulfided catalysts. The catalysis results revealed that the hydrogenation pathway was predominant in the HDS of DBT. A NiMo catalyst synthesized with 0.5g PVP showed a higher conversion of DBT than the other NiMo catalysts, possibly due to efficient formation of the ‘NiMoS’ active phase. This facile, scalable, and cost-effective route to prepare unsupported NiMo catalyst with enhanced HDS activities would be attractive in industrial applications.

Hydrophilization of polysulfone hollow fiber membranes via addition of polyvinylpyrrolidone to the bore fluid

The novel method of modification of hollow fiber membranes from polysulfone is proposed. The method involves the use of aqueous solutions of polyvinylpyrrolidone (PVP) as a bore fluid in the dry-jet wet spinning process. Increasing PVP concentration (1–5wt%) in the bore fluid was found to yield in the efficient hydrophilization of the inner skin layer of the hollow fiber membrane. The contact angle of the skin layer was found to decrease from 76° down to 54° when the PVP concentration in the bore fluid is 1wt% and down to 45° – at 5wt%. The FTIR-spectra studies reveal the presence of PVP only on the inner surface of the modified hollow fiber membrane while outer surface was found to represent unmodified polysulfone. Scanning electron microscopy and atomic force microscopy studies reveal a difference in the structure of the initial and modified membranes. Introduction of PVP into the bore fluid leads to the marked changes in membrane pure water permeability and rejection. When the bore fluid contains 5wt% of PVP, the rejection coefficient for PVP (Mn=40 000gmol−1) was found to increase from 29% to 85%, and the pure water flux – to decrease from 370 to 130Lm−2 h−1bar−1 compared with the initial membrane. Antifouling characteristics against human serum albumin are shown to be significantly improved for the modified hollow fiber membranes compared with the initial membranes.

Preparation and Ferroelectric Properties of K0.5Na0.5NbO3 Thin Films Derived from Non-alcohol Niobium Salt Sol-gel Process

Lead-free K0.5Na0.5NbO3 (KNN) thin films were prepared on Pt (111) /Ti/SiO2/Si (100) substrates by a polyvinylpyrrolidone (PVP)-modified sol-gel method without any metal alkoxides. The effects of PVP on the crystallization, surface morphology and electrical properties were investigated. It was found that the introduction of PVP into the sol could reduce the annealing temperature, enhance the surface quality and improve the KNN film of (100) oriented growth. Compared with the pure non-PVP-modified KNN thin films, the dielectric and ferroelectric properties of the KNN films were significantly enhanced by adding PVP into the sol. In particular, the PVP-modified KNN films which were annealed at 550°C exhibited relatively saturated polarization-electric field (P-E) hysteresis loops with high remnant polarization Pr of 22 μC/cm2, dielectric constant of 280 and dielectric loss of 0.09, respectively, indicating promising lead-free piezoelectric film candidate for future applications.

Microwave-assisted synthesis of kC/Xylan/PVP-based blend hydrogel materials: physicochemical and rheological studies

Hydrogel systems composed of kC/Xylan (kC/OSX or kC/BX) blends and linear polyvinylpyrrolidone (PVP) were prepared in the presence of water soluble initiator sodium persulphate (KPS) with microwave irradiation. The hydrogel materials were investigated by measuring their syneresis, swelling, gel fraction, and rheological properties. Physicochemical and rheological properties of the natural polysaccharide (kC/Xylans) blends were modified significantly after blending with PVP. The introduction of PVP and the formation of semi-interpenetrating polymer network (semi-IPN) structure improved the gelling properties of the resulting hydrogels. It has been proven, that a high incorporation of PVP could only be obtained if the hydrogels were prepared using KPS initiator and microwave irradiation in combination. FTIR, CP-MAS 13C NMR, and elemental analysis confirmed the presence of PVP in the blends but no direct evidence for covalent bonds could be obtained.

Synthesis and surfactochromicity of 1,4-diketopyrrolo[3,4-c]pyrrole(DPP)-based anionic conjugated polyelectrolytes

Two novel anionic conjugated copolyelectrolytes PSDPPPV and PSDPPPE were synthesized via Heck/Sonogashira coupling reactions and characterized by FT-IR, 1H NMR, UV-vis, and PL spectroscopy. The two polymers are respectively constituted of 2,5-diethoxy-1,4-phenyleneethynylene (DPV) and 2,5-diethoxy-1,4-phenyleneethynylene (DPE) with 1,4-diketo-2,5-bis(4-sulfonylbutyl)-3,6-diphenylpyrrolo[3,4-c]pyrrole (SDPP) which is a novel water soluble diketopyrrolopyrrole derivative. PSDPPPV and PSDPPPE show broad absorption band in visible region and they exhibit strong fluorescence quenching in aqueous solution. The fluorescence of their aqueous solutions can be enhanced in the presence of cationic surfactant or polymer nonionic surfactant. Fluorescence enhancement by introduction of polyvinylpyrrolidone (PVP) shows linear response. This result provides a controllable method to increase fluorescence intensity of dipyrrolopyrrole-based conjugate polyelectrolytes in aqueous phase. The optical properties suggested that PSDPPPV and PSDPPPE which are negatively charged conjugated polymers can assemble with positively charged photovoltaic materials to form ionic photoactive layer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 739–751

One-step fabrication in aqueous solution of a granular alginate-based hydrogel for fast and efficient removal of heavy metal ions

Granular alginate-based hydrogels were pre- pared in situ in an aqueous solution via grafting and crosslinking reactions among sodium alginate (SA), acrylic acid (AA), polyvinylpyrrolidone (PVP), and gel- atin (GE). Fourier transform infrared spectra, elemental analysis, and scanning electrical microscopy revealed that AA monomers were grafted onto an SA backbone, and that PVP and GE were present in the hydrogel network as linear interpenetrating components. The grafting polymerization and crosslinking reaction be- tween only SA and AA yielded a bulk gel, but the introduction of PVP and GE into the reaction mixture led to the formation of granular products. Electrostatic and hydrogen-bonding interactions among SA, PAA, PVP, and GE were the main driving forces for the formation of granular products. The adsorption iso- therms and adsorption kinetics were evaluated for the adsorption of model heavy-metal ions on one of the hydrogels. The results indicated that the hydrogel has satisfactory adsorption capacities (3.028 mmol/g, Ni 2+ ; 3.146 mmol/g, Cu 2+ ;2 .911 mmol/g, Zn 2+ ; 2.862 mmol/g, Cd 2+ ), adsorption rates, and recovery capacities for the target metal ions. In addition, competitive adsorption results suggested that the hydrogel has a stronger affin- ity for Cu 2+ ion than for the other ions.

The Preparation and the Properties of CS/PVP Composite Hydrogel Microspheres

According to the gelatification of sodium hydroxide ethanol solution, the chitosan (CS)/polyvinylpyrrolidone (PVP) composite hydrogel microspheres have been prepared in this paper. Meanwhile, the influence of PVP content and PH on the swelling property and the adsorption Cr(Ⅵ) effect of CS/PVP hydrogel microspheres has been also discussed. The results have shown that the introduction of PVP has significantly improved the swelling property of CS. When the CS content is 2.5% and the PVP content is 5%, the swelling rate of microspheres will be the maximum. The swelling property and the adsorption property of microspheres have shown certain pH sensitivity. And the SEM has also indicated that the inside of CS/ PVP composite hydrogel microspheres is the loose network structure, which is conducive to the swelling and the adsorption.

The influence of amphiphilic polymers on the photocatalytic activity of water-soluble porphyrin photosensitizers

The influence of amphiphilic polymers polyvinylpyrrolidone, poly(ethylene oxide), poly(vinyl alcohol), and pluronic F127 (propylene oxide-ethylene oxide triblock copolymer) on the catalytic activity of a number of water-soluble metal-free porphyrin photosensitizers was studied in the reaction of tryptophan photooxidation in aqueous solution. The introduction of the specified polymers was found to enhance the activity of carbon-substituted tetrafluorophenylporpyrin, photoditazine, and dimegin. It was ascertained that introduction of polyvinylpyrrolidone had the strongest effect on the increase in the photooxidation process rate; the change in the activity of porphyrins was 30–70%. The introduction of poly(ethylene oxide), poly(vinyl alcohol), and pluronic F127 was shown to enhance the rate of the process by 10–40%. It was concluded that this polymer effect was connected with the dissociation of aggregates, in which form porphyrin molecules were present in aqueous solutions, as indicated by an increase in fluorescence intensity of porphyrins. The introduction of polymers resulted in a bathochromic shift of the fluorescence bands for all porphyrins, which accounted for the formation of complexes of porphyrin sensitizers with the polymers.

Synthesis and swelling properties of pH-sensitive semi-IPN superabsorbent hydrogels based on sodium alginate-g-poly(sodium acrylate) and polyvinylpyrrolidone

A pH-sensitive semi-interpenetrating polymer network (semi-IPN) superabsorbent hydrogel composed of sodium alginate-g-poly(sodium acrylate) (NaAlg-g-PNaA) network and linear polyvinylpyrrolidone (PVP) was prepared by free-radical solution polymerization in the presence of initiator ammonium persulfate (APS) and crosslinker N,N-methylene-bis-acrylamide (MBA). FTIR results revealed that PNaA had been grafted onto NaAlg macromolecular chains and PVP was penetrated throughout the NaAlg-g-PNaA network by a hydrogen binding action. The surface morphologies of the hydrogels were improved due to the incorporation of PVP as shown by SEM observation. The introduction of PVP and the formation of semi-IPN structure greatly improved the water absorption and swelling rate of the hydrogel. The hydrogel possesses remarkable sensitivity to external pH stimulus and shows reversible On–Off switching swelling characteristic. An intriguing time-dependent swelling behavior of the semi-IPN hydrogel was observed in multi-valence saline and cationic surfactant solutions, but the similar time-dependent behaviors are resulting from two distinct mechanisms.

Volatilization of alkali ions and effects of molecular weight of polyvinylpyrrolidone introduced in solution-derived ferroelectric K0.5Na0.5NbO3 films

Ferroelectric K0.5Na0.5NbO3 (KNN) thin films were prepared by a chemical solution deposition approach with polyvinylpyrrolidone (PVP) of different molecular weights introduced in the precursor solutions. The volatilization of the alkali ions and the effects of the molecular weight of PVP were examined with x-ray diffraction (XRD), thermal analysis, mass spectrometry, and x-ray photoelectron spectroscopy (XPS). The results clearly showed that the volatilization of the alkali ions mainly happened at moderate temperatures before the crystallization of the KNN perovskite phase. Loss of Na was more significant than K ions during the heating process of KNN. The introduction of PVP with the appropriate molecular weight could effectively promote the crystallization of the KNN perovskite phase at reduced temperature and substantially suppress the loss of the alkali ions before crystallization. Therefore, a high dielectric constant, piezoelectric coefficient, and well saturated ferroelectric hysteresis loops were obtained in the KNN films in which PVP of the right molecular weight were introduced.

Directed Regulation of Biological Activity of Multicomponent Polymeric Structures

Biological activity of multicomponent polymeric films based on polyvinyl alcohol, polyvinylpyrrolidone, and lactic acid, containing trypsin and kanamycin, is studied. The degrees of degradation and biodegradation of multicomponent film coatings can be controlled by introduction of polyvinylpyrrolidone or lactic acid and also by variation in their electroforming parameters.