Structure and swelling-release behaviour of poly(vinyl pyrrolidone) (PVP) and acrylic acid (AAc) copolymer hydrogels prepared by gamma irradiation

Copolymer network hydrogels were prepared by gamma irradiation of aqueous solutions of poly(vinyl pyrrolidone) (PVP) and acrylic acid monomer (AAc). The composition of the final hydrogels compared to the composition of the initial preparation solutions of hydrogels was determined. The chemical structure and nature of bonding was characterized by IR spectroscopy analysis, while the thermal durability of the prepared hydrogels was assessed by thermogravimetric analysis (TGA). The kinetic swelling in water and the pH-sensitivity of PVP/AAc copolymer hydrogels was studied. The drug release properties of PVP/AAc hydrogels taking methyl orange indicator as a drug model was investigated. The IR spectra indicate the formation of copolymer networks, whereas the TGA study showed that the PVP/AAc hydrogels possess higher thermal stability than pure PAAc and lower than PVP hydrogels. The kinetic swelling in water showed that all the hydrogels reached equilibrium after 24 h and that the degree of swelling increases with increasing the ratio of AAc in the initial feeding solutions. It was found that the degree of swelling of PVP/AAc hydrogels increases greatly within the pH range 4-7 depending on composition.     

Keggin结构钨磷酸/聚乙烯吡咯烷酮复合膜的制备和光致变色性质研究

近年来,由于无机－有机复合材料具有潜在的应用前景和特殊性能,尤其是光致变色性能,引起研究者们的广泛兴趣^[1-3],以杂多化合物为多核配合物,通过化合键或氢键作用与高分子底物结合,形成电荷转移物质,可以大大提高复合材料的化学和物理性能。目前,这一领域的研究在国外已经成为热点^[4-7]。本文以Keggin结构钨磷酸和聚乙烯吡咯烷酮为原料,报道了该类复合物的合成、表征及光致变色性质。     

聚苯并咪唑/聚乙烯吡咯烷酮复合质子交换膜的制备及钒液流电池性能

将聚苯并咪唑(PBI)与聚乙烯吡咯烷酮(PVP)共混, 制备了一系列PBI/PVP复合质子交换膜, 研究了不同PVP含量对PBI/PVP复合质子交换膜性能的影响. 研究结果表明, PVP的加入可有效提高PBI/PVP复合质子交换膜的吸水率及硫酸吸附量, 从而提高质子电导率, 与PBI原膜相比, PBI-PVP-5复合质子交换膜的结合酸含量可达2.47 mmol/g, 质子电导率达4.81 mS/cm, 选择性(3.12×10⁵ S·min/cm³)远高于原膜(1.12×10⁵ S·min/cm³). 电流密度为120 mA/cm²时, 电池的电压效率(VE)和能量效率(EE)均较PBI原膜提高了10%, 电池自放电时间长达307 h. PVP的加入为PBI系列钒液流电池隔膜提供了一个提高质子电导率的新思路.     

Synthesis and Characterization of Water-Soluble Graft Copolymers from 2, 3-Dihydroxypropylcellulose and Acrylamide

Water-soluble 2,3-dihydroxypropylcellulose-polyacrylamide graft copolymers (DHPC-g-PAM) were prepared by Ce⁴⁺ ion-initiated graft copolymerization of acrylamide (AM) onto 2,3-dihydroxypropylcellulose (DHPC) dissolved in dilute nitric acid at room temperature under argon. The ratios of the concentration of Ce⁴⁺ ion to the concentration of DHPC were shown to affect the number and the length of the polyacrylamide grafts. The average number of grafts per chain was determined by acid-catalyzed degradation of the cellulose backbone and was found to be consistent with the presence or absence of free DHPC in the polymerization product prior to hydrolysis. The average number of grafts per DHPC molecule was found to be 2.7 or less depending on the reaction conditions.     

A novel route to substituted poly(vinyl pyrrolidone)s via simple functionalization of 1-vinyl-2-pyrrolidone in the 3-position by ring-opening reactions

A general synthetic approach is described that allows to obtain novel 1-vinyl-2-pyrrolidone (VP) derivatives with different kinds of functional groups in its 3-position in a one-pot reaction. The strategy used to achieve this goal is the reaction of the carboxamide anion of 1-vinyl-2-pyrrolidone with cyclic precursors of these functionalities. While the driving force for the reactions of three-membered rings is their high annular tension, it is shown here that larger heterocycles can be opened with good yield when additional electron-withdrawing groups are present in the ring. This leads to VP with longer spacer groups between the functionality and the future polymeric main chain. Furthermore, the high versatility of this procedure is demonstrated by the preparation, for the first time, of VP modified with amine or sulfonic functionalities that allow to prepare the corresponding aminated and sulfonated PVPs.     

Dielectric Dispersion Study of Poly(vinyl Pyrrolidone)–Polar Solvent Solutions in the Frequency Range 20 Hz–1 MHz

Influence of polar solvents environment and polymer concentrations on the electrical properties (complex dielectric constant, ac electrical conductivity, complex electric modulus and complex impedance) of the solutions of poly(vinyl pyrrolidone) (PVP) in polar solvents, namely water, ethyl alcohol, ethylene glycol, diethylene glycol, poly(ethylene glycol), glycerol, dimethyl sulfoxide and dimethyl formamide, have been investigated in the frequency range 20 Hz–1 MHz at 25°C. Comparative analysis of the dielectric dispersion curves confirms that the solvent molecular size and number of its hydroxyl groups, and the solutions viscosity, are the major factors which governs the PVP chain segmental motion. The ionic conduction and electrode polarization phenomena has a dominant influence on the large increase of complex dielectric constant values of the solutions of PVP‐polar solvent in the lower frequency region. The values of relaxation times corresponding to these phenomena are also reported.     

成膜剂对染料敏化太阳电池性能的影响

通过刮涂法将P25粉的乙醇体系配制的TiO_2浆料制备成光阳极中的TiO_2薄膜,在TiO_2浆料中分别加入聚乙烯吡咯烷酮(PVP)和乙基纤维素(M70),作对比实验,研究发现加入PVP制备的TiO_2薄膜的宏观和微观结构都得到了明显的改善,其影响了TiO_2薄膜的孔隙率、比表面积和染料的吸附量,显著改善了染料敏化太阳电池性能,短路电流由5.59 mA/cm~2增到11.31 mA/cm~2,电池效率由2.70;增到5.31;(AM1.5).     

Photochemical synthesis of copper nanoparticles incorporated in poly(vinyl pyrrolidone)

The effect of the presence of poly(vinyl pyrrolidone) (PVP) on the copper nanoparticle formation, obtained by UV irradiation of ethanol solution of Cu(acac)₂ (acac = 2,4-pentanedionato), was investigated. At 254 nm, in conditions of light completely absorbed by complex, the PVP exhibited protective and stabilizing effects, as shown by the formation of a colloidal copper solution and by a block of the heterogeneous process, which leads to thin film formation on the quartz walls. The colloidal solution was tested for several months by plasmon position and it was found that it remained unaltered in inert atmosphere, but returned to the starting complex on contact with air. The PVP ability to control the particle size was investigated by carrying out photoreduction sensitized by Hacac at 254 and 300 nm, in the presence of PVP concentration varying from 0 to 0.2 M. In this range it was possible to obtain copper nanoparticles of dimensions decreasing from 30 to 4 nm. Besides this, the PVP (0.005–0.05 M) role as sensitizer was investigated by irradiating solutions of Cu(acac)₂ at 300 nm which is an inactive wavelength for copper reduction by direct light absorption. It was found that the PVP was an efficient sensitizer of the copper photoreduction. The nanoparticles were characterized by plasmon band, Trasmission Electron Microscope (TEM) as well as Dynamic Light Scattering (DSL) analysis. The overall results evidence the advantages of the PVP use in the nanoparticle copper formation through the photochemical technique such as the exclusive formation of colloidal copper, their size control, stable colloidal solution and complete return to the starting complex.     

Determination of an optimal modifier for albumin for medicobiological technology by the X-ray photoelectron spectroscopy method

The interatomic interaction of albumin and a modifier is studied with the use of the X-ray photoelectron spectroscopy method. As the result of the study of the albumin nanomodification, an optimal modifier for albumin is determined. It is shown that the compatibility of bio- and nanostructures depends on their dimension. The modification of albumin with carbon copper-containing nanotubes leads to the albumin thermal stability up to the temperatures in the range of 525–537 K. However, the modification of albumin with carbon nickel-containing nanotubes, the radius of which is much smaller than that of carbon copper-containing nanotubes, leads to the destruction of albumin at room temperature. The dependence of the thermal stability of protein modified with vinyl pyrrolidone acrolein diacetal copolymer on its content in the mixture is found. The growth of the temperature of stabilization with the increasing content of vinyl pyrrolidone acrolein diacetal copolymer is shown.     

Electrospinning method for the preparation of silver chloride nanoparticles in PVP nanofiber

It has been successfully developed by the electrospinning technology that AgCl nanoparticles were incorporated into polymer fiber. In this paper, we chose poly(vinyl pyrrolidone) (PVP) because it was not only a good material for electrospinning but also it was excellent capping reagent of various metal nanoparticles. The silver ions interacted with the carbonyl groups in the PVP molecules. The formation of AgCl nanoparticles inside the PVP were carried out via the reaction of silver ions and HCl. TEM proved that most of the AgCl nanoparticles were uniformly dispersed in the PVP fibers.