Addition Of PVP Research Articles

The Effect of PVP Addition and Heat-treatment Duration on Zinc Oxide Nanoparticles

The Effect of PVP Addition and Heat-treatment Duration on Zinc Oxide Nanoparticles

Poly(vinylpyrrolidone)-doped nitric oxide-releasing xerogels as glucose biosensor membranes

Nitric oxide (NO)-releasing xerogel membranes were prepared as coatings for an electrochemical glucose biosensor to allow for enhanced biocompatibility while maintaining adequate response times and sensitivity. Formation of the NO-donor species was found to drastically decrease the permeability of the aminosilane-based xerogels to both hydrogen peroxide and glucose. The addition of poly(vinylpyrrolidone) (PVP) polymer enhanced the membrane permeability even after exposure to high pressures of NO (necessary for NO-donor synthesis). The analytical response and NO release of PVP-doped NO-releasing xerogels as glucose sensor membranes were further investigated and found to be enhanced via polymer doping. Doping of the polymer into the xerogel did not compromise the stability of the xerogel as evaluated by silicon leaching studies. Despite the addition of PVP, the NO-releasing xerogels maintained reduced bacterial adhesion characteristics analogous to previous reports for NO-releasing xerogels.

Preparation and characterization of monodisperse nickel nanoparticles by polyol process

Polymer-protected monodisperse nickel nanoparticles were synthesized by a modified polyol reduction method in the presence of poly (N-vinyl-2-pyrrolidone). These nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), selected area electron diffraction (SAED), as well as vibrating sample magnetometer (VSM). The experimental results show that the addition of PVP and the concentration of NaOH have strong influences on the size, agglomeration and uniformity of nanoparticles. In the presence of PVP and NaOH with low concentrations, monodisperse nickel nanoparticles with average diameters about 42 nm were obtained and characterized to be pure nickel crystalline with fee structure. Secondary structures such as clusters, loops, and strings resulted from magnetic interactions between particles were observed. The chemical interaction between the PVP and nickel nanoparticles was found by FTIR. The saturation magnetization (Ms), remarem magnetization (Mr) and coercivity (HC) of these nickel nanoparticles are lower than those of balk nickel.

Influence of salt and polymer on the critical vesicle concentration in aqueous mixture of zwitterionic/anionic surfactants

Vesicles can be formed spontaneously in aqueous solution of surfactant mixture of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and lauryl sulfonate betaine (LSB). Different from the catanionic vesicles, the formation is dependent on surfactant concentration, mixing ratio and salinity due to the weak attraction between the two kinds of surfactant molecules, which provides possibility to determine the critical vesicle concentration (CVC), just as the critical micelle concentration (CMC). In this paper, a simple but sensitive conductivity titration was employed to determine the critical concentration since it is concentration-continuous and the structural transition of the ionic surfactant relates directly to their conductivity. Especially, after vesicles are formed, some of the surfactant molecules form the inner layer of the vesicle and do not conduct any more, which will lead to a much evident change in conductivity. As a result, the turning points appear in both the conductivity and molar conductivity titration curve at the transition from monomers to micelles and micelles to vesicles with increasing concentration and/or salinity, with assistant proof from surface tension measurement and TEM. The CVC drops markedly after the addition of salt due to the compression of salt on the double electric layer of the surfactant polar head. But the addition of nonionic polymer PVP (K30) delays the vesicle formation due to the adsorption of surfactant molecules to the polymer. The results may make much contribution to the understanding of the mechanism of vesicle formation.

Comparison between the binding of chlorpheniramine maleate to poly(sodium 4-styrenesulfonate) and the binding to other polyelectrolytes

Abstract The interactions of the antihistaminic drug chlorpheniramine maleate (CPM) with the negatively charged polyelectrolytes poly(sodium 4-styrenesulfonate) (PSS) and poly(acrylic acid) (PAA) are studied by the washing method of the diafiltration technique at conditions simulating those of the small intestine such as pH 7.5 and 0.13 M NaCl. The results are compared with those already reported involving other pharmacologically important polyelectrolytes such as alginic acid (ALG), carboxymethylcellulose (CMC), and κ- and ι-carrageenan (κ- and ι-CAR). As in the case of ALG, CMC, and CAR, interactions of CPM with PAA appear to be electrostatic and are cleaved in the presence of 0.13 M NaCl. On the contrary, apart from electrostatic interactions, additional interactions are found with PSS and residual interactions are kept in the presence of 0.13 M NaCl, a fact that may be attributed to π–π interactions and hydrophobic forces. The effect of the addition of 4 M urea, branched poly(ethyleneimine) (BPEI), and poly(vinylpyrrolidone) (PVP) is also studied. The addition of urea 4 M or 0.001 M BPEI produces a decrease on the amounts of counterions bound to PSS at infinite elution, while the addition of PVP does not produce any change on the diafiltration profiles.

Effect of PVP Addition on Microstructure of SrZrO<sub>3</sub> Thin Films on Bi(2223) Tapes

SrZrO3 resistive oxides on Ag sheathed Bi(2223) tapes were prepared by the sol-gel and dip-coating method to investigate the effect of PVP content and thermal stage on microstructure of the films. Although film thickness rose with the addition of PVP, the amount of PVP was not effective to reduction in the crack density of the films. However, longer drying time at low temperature and shorter heat treatment time at 500oC were effective for controlling the microcracks of the SrZrO3 films, indicating that the microcracking of the films was governed primarily by the thermal stage.

Asymmetric membrane capsules for delivery of poorly water-soluble drugs by osmotic effects

A non-disintegrating polymeric capsule system, in which asymmetric membrane offers an improved osmotic effect, was used to deliver poorly water-soluble drugs in a control manner. The capsule wall membrane was made by a phase inversion process, in which asymmetric membrane was formed on stainless-steel mold pins by dipping the mold pins into a coating solution containing a polymeric material followed by dipping into a quench solution. This study evaluates the influence of coating formulation that was cellulose acetate (CA), ethylcellulose (EC), and plasticizer (glycerin and triethyl citrate). Results show capsule that made by CA with glycerin (formulation A), which appear in asymmetric structure and are able to release chlorpheniramine maleate (CM) in significant percentage. Two poorly water-soluble drugs of felodipine (FL) and nifedipine (NF) were selected as the model drug to demonstrate how the controlled release characteristics can be manipulated by the design of polymeric capsules with an asymmetric membrane and core formulations. Results show that sodium lauryl sulfate (SLS) is able to promote the release of FL from polymeric capsules prepared with CA with asymmetrical membrane. The addition of solubilizer, including RH40, PVP K-17, and PEG 4000 could enhance the release of FL but with an extent not being related to its solubility. Based on these results, influence of core formulation variables, including the viscosity and added amount of hydroxypropyl methylcellulose (HPMC), the added amount of SLS, and drug loading were examined on the release of NF. It was found that HPMC of 50 cps was suitable to be a thickening agent and both added amount of HPMC and SLS showed a comparable and profoundly positive effect, whereas NF loading had no influence on the drug release percent and rate. There existed a synergistic interaction between HPMC and SLS on the release percent and rate.

Viscosity B-coefficients and activation free energy of viscous flow for hexanedioic acid in aqueous polyvinylpyrrolidone solution

Viscosity and density data for the ternary solution of hexanedioic acid + polyvinylpyrrolidone (PVP k30) + water at temperatures 298.15, 303.15, 308.15 and 313.15 K have been measured. On the basis of the Eyring and Feakins equation, the viscosity B-coefficients and the activation parameters for viscous flow of the solution have been evaluated. The effect of temperature and PVP concentration on these parameters has been discussed. With the increase in PVP concentration, the activation free energy of diffusion for hexanedioic acid is decreased. This is an indication that the diffusion ability of hexanedoic acid is improved by the addition of PVP into solution.

Effect of hypochlorite concentration on properties of posttreated outer‐skin ultrafiltration membranes spun from cellulose acetate/poly(vinyl pyrrolidone) blends

AbstractAn outer‐skin hollow‐fiber ultrafiltration (UF) membrane was spun from a new dope solution containing cellulose acetate (CA)/poly(vinyl pyrrolidone) (PVP 360K)/N‐methyl‐2‐pyrrolidone (NMP)/water using a wet‐spinning technique. The as‐spun fibers were posttreated with a hypochlorite solution over a range of concentrations for a fixed period of 24 h. The experimental results showed that the pure water flux of the treated membrane increased with increasing hypochlorite concentration. The treated membrane experienced an increased fouling tendency with increasing hypochlorite concentration because the hydrophilicity of the treated membrane decreased as a result of the removal of PVP contents in the membrane matrix after hypochlorite treatment. SEM images revealed that the membrane had an outer dense skin, a porous inner surface, and a spongelike structure, which confirmed that addition of PVP favored the suppression of macrovoids in the membrane. The membrane pore size could be significantly increased when the hypochlorite concentration reached 200 mg/L. It was concluded that hypochlorite treatment provided an additional option to easily alter the pore size of UF membranes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 227–231, 2005

폴리올법에 의한 편상의 은 분말 합성

【Monodispersed flaky silver powder was obtained by controlling the ratios of $H_{2}O_{2}/NH_{3}$ and Agin in a mixed solution of ethylene glycol and ammonia with an addition of PVP. The effects of $NH_{3}/Ag,\; H_{2}O_{2}/Ag\;and\;H_{2}PtCl_{6}/Ag$ on its morphology and size were investigated. In $H_{2}O_{2}-NH_{3}-AgNO_{3}\;system,\;NH_{3}/Ag$ molar ratio was found to be an important reaction factor for the nucleation and crystal growth of Ag powder. The synthesis of flaky powder was optimized at over 6 of $NH_{3}/Ag \;and\;5\;of\;H_{2}O_{2}/Ag\;under\;1.0{\times}10^{-3}\;of\;Pt/Ag.\;Moreover,\;as\;the\; NH_{3}/Ag$ molar ratio increased, the size of precipitates was increased regardless of the amount of Pt. In the absence of $H_{2}PtCI$ , the morphology and size of reduced Ag powder were found to be irregular in shape $2-4{\mu}m$ in diameter. However, homogenized fine Ag powder was obtained due to heterogeneous nucleation when $H_{2}PtCI$ used as a cat-alyst, and flaky one was synthesized with the addition of Pt over $1.0{\times}10^{-3}$ of Pt/Ag.】

The fabrication and properties of solid polymer electrolytes based on PEO/PVP blends

New solid polymer electrolytes were fabricated by the addition of lithium perchlorates in the blends of polyethylene oxide (PEO, MW = 5 × 10 6) and poly-4-vinylpyridine (PVP, MW = 1.6 × 10 6). Not only the coordinating bonding between ether units (–O–) of PEO and Li + ions at about 1100 cm −1 but also the existence of pyridine salts at about 3500 cm −1 were definitely observed in the FT-IR spectra. The addition of PVP in the PEO matrix is to restrict mobility of ClO 4 - ions through the coupling of PVP and ClO 4 - ions. Therefore, the increase of PVP content is expected to decrease the self-discharge rate. In the case of PEO–PVP blends without LiClO 4, the melting temperature T m and the degree of crystallinity were decreased by the increase of PVP content. On the contrary, those of PEO–PVP blends with LiClO 4 were increased with the increase of PVP content. The results can be explained lay ClO 4 - ions, which reduced the crystallinity of PEO by steric hindrance, segregated from the PEO by the coupling of PVP and ClO 4 - ions. The new solid polymer electrolytes based on PEO–PVP blends showed ionic conductivities of the order of 10 −8 to 10 −7 S/cm.

Influence of the addition of PVP on the morphology of asymmetric polyimide phase inversion membranes: effect of PVP molecular weight

A macrovoid-free, porous membrane with a sponge-like structure was obtained by phase inversion of a polyimide (PI)/γ-butyrolactone (GBL)/water system, whereas a membrane with a finger-like structure was obtained from a PI/ N-methyl-2-pyrrolidinone (NMP)/water system. In this study, the effect of the molecular weight of poly(vinyl pyrrolidone) (PVP) additive ( M w: 360k and 40k) in two systems on membrane morphology has been investigated by the differences in phase separation rates and miscibility gaps. On addition of PVP into the PI casting solutions, the two systems exhibited significantly different membrane morphologies; the former augmented macrovoid formation while the latter suppressed formation of finger-like structures. The membrane morphology and the phase separation rate significantly depend on the molecular weight of PVP in PI/NMP/water system whereas those do insignificantly in PI/GBL/water system. The cloud points representing the miscibility gap do not depend on the molecular weight of PVP in both systems very much. Therefore, it is suggested that the morphology change in the PI/NMP/water system is mostly due to the change in the phase separation rate caused by the change in the solution viscosity upon addition of PVP. However, in the PI/GBL/water system, the molecular weight effect of PVP is not as significant as in the PI/NMP/water system, and the morphology change seems to be primarily due to the change in the miscibility gap.

Twin screw granulation as a simple and efficient tool for continuous wet granulation

The modification of a twin screw extruder for continuous wet granulation was investigated. Modification of the extruder setup as well as the screw design allowed the continuous wet granulation of α-lactose monohydrate without the need of a wet sieving step. The robustness of twin screw granulation was evaluated by studying the influence of processing parameters and formulation variables on the process performance and on the properties of α-lactose monohydrate granules and tablets. The process reproducibility during long term production was evaluated. Screw speed (200–450 rpm) and total input rate (5.5–9.5 kg/h) had no significant influence on the granule properties, while the water concentration during granulation influenced the process as well as the granule properties. At a water concentration (calculated on wet granule basis) of 5.5–8.5%, continuous twin screw granulation of α-lactose monohydrate 200M was feasible and the granules obtained had good properties. PVP addition mainly affected tablet properties. Tablets made from granules containing 2.5% PVP had a tensile strength above 0.94 MPa, a friability below 1% and a disintegration time ranging between 495 and 576 s. Tablets containing hydrochlorothiazide complied with the dissolution requirements as 60% was released after 5 and 15 min from tablets without PVP and with 2.5% PVP, respectively. No problems were observed during continuous twin screw granulation over a period of 8 h and the granule and tablet properties were reproducible throughout the process. These results indicated that twin screw granulation is an efficient tool for continuous wet granulation.

Effect of anionic surfactant–polymer complexes on the crystallization of calcium carbonate

The synthesis of calcium carbonate (CaCO 3) crystals from aqueous solutions containing anion surfactants (sodium dodecylsulfonate (DDS), sodium dodecylbenzenesulfonate (SDBS)) or anionic surfactant–poly( N-vinyl-1-pyrrolidone) (PVP) complexes has been performed by the method of rapid mixing of the solutions of calcium chloride (CaCl 2) and sodium carbonate (Na 2CO 3), followed by 10-h incubation under stirring. Polymorphism of CaCO 3 crystals was observed in different additive systems. In pure anionic surfactant systems, DDS induced the transformation of initially formed amorphous CaCO 3 to calcite, while SDBS favored the formation of vaterite as the final product. The addition of PVP into the above two anionic surfactant systems, promoting the formation of supermolecular complexes of surfactant/polymer, resulted in a distinct variation of the morphology of CaCO 3 crystals. The polymorphs of CaCO 3 are dependent not only on PVP but also on DDS or SDBS concentrations in the complex solution, i.e., anionic surfactants control the crystalline phase, but PVP only changes the crystal shape.

Trade-off between thermodynamic enhancement and kinetic hindrance during phase inversion in the preparation of polysulfone membranes

Polysulfone membranes were prepared via the diffusion-induced phase inversion process from casting solutions consisting of polysulfone, dimethyformamide, and polyvinyl pyrrolidone as a polymeric additive. The effect of PVP added in casting solutions was analyzed by measuring the prepared membranes' morphology and water permeability. Variations in a casting solution's thermodynamic and kinetic properties caused by PVP addition suggest that the thermodynamic variation works in favor of the enhancement of demixing in the casting solution, but the rheological variation induces the opposite trend, or the delay of demixing. When prepared by the immersion coagulation into a water bath, the solidified membranes' structural and functional properties indicate that the coagulation of cast solutions was affected by the trade-offrelationship between thermodynamic enhancement and kinetic hindrance. With a small amount of PVP in the casting solution, the thermodynamic driving force played a major role on solution demixing, inducing the demixing enhancement, corresponding to the acceleration of phase separation due to the PVP's nonsolvent effect. Consequently, the PVP acts as a phase separation enhancer, resulting in both macropore enlargement and permeate flux increase. With more addition of PVP, however, the macropore structure and the water permeability were suppressed rather than enlarged or increased. These phenomena reflect that the demixing of the cast solution was delayed, with the kinetic hindrance offsetting the thermodynamic effect for phase separation enhancement.

Influence of polyvinylpyrrolidone on the precipitation of calcium carbonate and on the transformation of vaterite to calcite

The precipitation process of calcium carbonate (CaCO 3) in the absence and presence of poly (N-vinyl-2-pyrrolidone) (PVP) was investigated using scanning electron microscopy, powder X-ray diffraction, and Fourier transform infrared spectroscopy methods at room temperature. The results indicate that PVP does not affect the polymorphy, but has influence on their morphology and size of CaCO 3 crystals. With the addition of PVP, the amorphous CaCO 3 could aggregate into bigger amorphous spherulites before transforming to crystalline state. Also, the transformation from the thermodynamically unstable vaterite to the stable calcite was investigated in the presence of PVP. As a particle-stabilizing agent, PVP molecules inhibit the formation of vaterite, however, promote the formation of calcite as well as the rate of the solvent-mediated transformation from vaterite to calcite.

Elimination of Surface Spallation of Alumina Green Bodies Prepared by Acrylamide‐Based Gelcasting via Poly(vinylpyrrolidone)

Surface spallation of gelcast alumina green bodies due to the exposure of the surface to air during gelation was successfully eliminated by adding a proper amount of poly(vinylpyrrolidone) (PVP) in aqueous acrylamide premix solution. The influences of PVP on the colloidal characteristics of alumina powder in aqueous solutions, the rheological properties of alumina slurries, the gelation process, and the properties and microstructures of the gelcast green bodies and the sintered samples were systematically investigated. Even though the addition of PVP to premix solution has slightly negative effects on the viscosity of alumina slurries, gelation and strength of green bodies, it has no obvious influence on the final structure and properties of alumina ceramics. Thus, PVP was considered an effective polymer to resolve the problem of the inhibition of gelation due to the presence of oxygen, which usually occurs in gelcasting during the formation of polymer network gel by in situ polymerization of monomers in air. The mechanism of PVP in eliminating the surface spallation problems of green bodies is also discussed.

Effect of PVP Additive on Porous Polysulfone Membrane Formation by Immersion Precipitation Method

Polysulfone (PSf) membranes were prepared by the immersion precipitation method from casting solution of PSf and a water-soluble polymer, poly(vinyl pyrrolidone) (PVP), in dimethylacetamide. The effect of the molecular weight of PVP on the phase separation rate during the porous membrane formation was investigated by the light scattering method. The plots of scattered intensity against scattered angle showed maxima, which indicated that the phase separation occurred by spinodal decomposition. The structure growth rate remarkably enhanced by the addition of PVP with the lower molecular weight due to both the deeper quench depth and the lower polymer concentration brought about by the PVP leaching into nonsolvent bath. The increase of PVP molecular weight resulted in a decrease of the structure growth rate. Moreover, with the increase of the molecular weight of PVP, the membrane structures were changed from a macrovoid structure to a sponge structure.

Ion exchange of strontium and caesium ions using PAN-4A composite ion exchanger

To modify the porosity of PAN-4A composite beads, PVP polymer was used. The optimum viscosity of the dope for the preparation of spherical beads is 470≈480 cP. The porosity of composite beads was increased up to 75 percent (by volume) at the ratio of PVP/PAN=1.0. PAN-4A composite beads were stable in acid solution of pH=2 and radiation dose up to 1.89 MGy. The ion exchange tests showed that PAN-4A composite ion exchanger was selective for Sr2+. Distribution coefficients for Sr2+ and Cs+ at pH=2 were 2×104 mL/g and 280 mL/g, respectively. Ion exchange capacities (Qm) modelled by Dubinin-Polanyi equation were 3.92 meq (Sr2+)/g and 2.47 meq (Cs+)/g, respectively. The uptake rates of PAN-4A for Sr ions were improved by PVP addition. The total effective diffusivities were of the order of 10−8 cm2/sec for both strontium and caesium ions.

Interaction Forces on α-Alumina Surfaces with Coadsorbed Anionic Surfactant and Nonionic Polymer

Direct measurements of interaction forces between α-alumina surfaces with coadsorbed anionic surfactant (sodium dodecyl sulfate (SDS) or lithium perfluorooctanesulfonate (LiFOS)) and nonionic polymer poly(vinylpyrrolidone) (PVP) at pH 3.5 are carried out by colloidal probe atomic force microscopy. In aqueous SDS solutions, the strength of interaction forces is found to depend on the initial SDS concentration, whereas in PVP solutions, the electric double layer interaction is completely screened due to the flat conformation of PVP on α-alumina. The interaction forces are dramatically different for the coaddition of SDS and PVP: electrostatic repulsion is observed above the critical aggregation concentration, and virtually no steric hindrance due to adsorbed polymer chains can be detected. These coaddition effects are attributed to the flat conformation of the adsorbed PVP and the formation of SDS−PVP surface complexes as confirmed by surface tensiometry. The LiFOS−PVP system exhibits characteristics similar to those of the SDS−PVP system, except that the repulsion between adsorbed LiFOS layers is remarkably weak at concentrations above its critical micelle concentration. The effects of sequential addition of SDS and PVP are also investigated.