Preparation of Ultrafine Water-soluble Polymers Nanofiber Mats via Electrospinning

A series of water-soluble polymers such as poly(ethylene oxide)(PEO),polyacrylamide(PAM) and poly(vinyl pyrrilidone)(PVP) was successfully prepared via the electrospinning of their aqueous solutions without the use of a surfactant.The effects of solution properties on the electrospinning of PEO,PAM and PVP solutions were investigated.The viscosity of the solution,charge density carried by the jet,and the surface tension of the solution are the key factors that influence the morphology and diameter size of t...     

Adjusting drug release by using miscible polymer blends as effective drug carries

In the present study PVP/HPMC and PVP/Chitosan polymer blends were prepared by using the solvent evaporation technique. From DSC studies were revealed that both blends are completed miscible in the entire composition range since only one glass transition temperature was detected. Miscibility can be attributed to the strong interactions evolved between the carbonyl group of PVP, which acts as strong proton acceptor, with hydroxyl and amino-groups of HPMC and Chitosan, which are proton donors. Thus hydrogen bonds are easily formed, as was verified by FTIR, producing miscible blends. However, the extent of interactions depends from polymer composition and mainly from the ratio and the kind of reactive groups. In PVP/HPMC blends a negative variation of T_g is recorded while in PVP/Chitosan the variation has a sigma form. The miscibility of these systems creates matrixes with completely different physical properties in order to use as effective drug carriers. PVP/HPMC blends can be used as pulsatile chronotherapeutics systems adjusting exactly the time of the drug release while PVP/Chitosan blends can be used to control the release profile of a poorly water soluble drug. In these blends HPMC and Chitosan respectively are the control factors for the corresponding applications.     

醋酸纤维素／聚乙烯基吡咯烷酮共混体系的特殊相互作用表征（Ⅱ）

通过测定醋酸纤维素（ＣＤＡ）和聚乙烯基吡咯烷酮（ＰＶＰ）共混物溶液的绝对粘度和特性粘数，发现ＣＤＡ和ＰＶＰ分子链段间有缔合现象．用富里哀变换红外光谱（ＦＴＩＲ）研究了共混物的吸收光谱，发现共混物中ＣＤＡ的羟基吸收峰和ＰＶＰ的羰基吸收峰均向低频方向迁移，证明了ＣＤＡ的羟基和ＰＶＰ的羰基之间有氢键形成．研究结果表明ＣＤＡ和ＰＶＰ的相容性及其特殊相互作用来源于不同分子链段间的氢键相互作用．     

醋酸纤维素／聚乙烯基吡咯烷酮共混体系的特殊相互作用表征（Ⅱ）

通过测定醋酸纤维素（ＣＤＡ）和聚乙烯基吡咯烷酮（ＰＶＰ）共混物溶液的绝对粘度和特性粘数，发现ＣＤＡ和ＰＶＰ分子链段间有缔合现象，用富里哀变换红光谱（ＦＴＩＲ）研究了共混物的吸收光谱，发现共混物中ＣＤＡ的羟基吸收峰和ＰＶＰ的羰基吸收峰均向低频方向迁移，证明了ＣＤＡ的羟基和ＰＶＰ的羧基之间有氢键形成，研究结果表明ＣＤＡ和ＰＶＰ的相容性及其特殊相互作用来源于不同分子链段间的氢键相互作用。     

An investigation on the influence of a vinyl pyrrolidone/vinyl acetate copolymer on the moisture permeation, mechanical and adhesive properties of aqueous-based hydroxypropyl methylcellulose film coatings

Polymers for aqueous film coating, such as hydroxypropyl methylcellulose (HPMC), often require the inclusion of a plasticizer to reduce brittleness and increase flexibility and ductility. A vinyl pyrrolidone/vinyl acetate copolymer (S630) was investigated for its influence on HPMC film coating parameters, comparing the results with a commonly used plasticizer, polyethylene glycol and another copolymer, polyvinyl alcohol. The viscous properties of the solutions and the glass transition temperatures of the equivalent polymer films were evaluated. Its effect on the film properties, such as appearance, surface roughness, moisture permeation and mechanical properties, as well as its ability to promote better adhesion of the film coat to the core surface, was compared. S630 was able to reduce the viscosity of the polymer solution and glass transition temperature of HPMC, as well as, enhance the mechanical properties of the cast film. The moisture permeation was slightly reduced but not to the same extent as polyethylene glycol. A 10% concentration of S630 increased the adhesive strength and toughness of the HPMC film coat. In conclusion, S630 was effective as a film-former, substrate adhesive and plasticizer. It has the potential to be used to replace the more volatile plasticizers which have problems of loss or migration.     

Structural influence of mono and polyhydric alcohols on the stabilization of collagen

In the present study, solvents effects on the structure of collagen have been examined by circular dichroism and their interfacial tension at glass/liquid and Teflon/liquid. Changes in the conformations of the protein have been analyzed after equilibration with aqueous solutions of monohydric and polyhydric alcohols like methanol, ethanol, n-propanol, propane-2-diol and glycerol. The results from viscosity and Circular dichroism (CD) spectra suggest a clear distinction in the structural changes for collagen with monohydric alcohols as against polyhydric ones. The surface tension and interfacial tension at glass (high surface energy, HFSE) and Teflon (Low surface energy, LSFE) reflect similar differences between the monohydric and polyhydric alcohols. Studies on the interfacial energy of the adsorbed protein at glass/solution interface compared to that of Teflon/solution interface show that the water structure near glass gets perturbed leading to an increase in the average free energy of the bulk water phase and a reduction in hydrophobic effect near the glass. The results suggest that the different solvents alter the hydrophobic effect on the hydrated protein to different extent and thus influence folding equilibrium of the protein without directly interacting with it. Polyhydric alcohols seem to favor the native collagen structure while monohydric alcohols enhance it.     

Surface Properties of Polyacid–Poly(N-Vinyl Pyrrolidone) Complexes

The effect of the complexation of polyacrylic (PAA) and polymethacrylic (PMAA) acids with poly(N-vinyl pyrrolidone) (PVP) on their surface properties was studied by measuring surface tension, conductivity, and the viscosity of aqueous mixed polymer solutions, as well as by the potentiometric titration at 293.15 K. The values of relaxation times and the surface activity of polycomplexes were calculated from kinetic data and the surface tension isotherms of the solutions. The complexation was found to increase the surface layer relaxation time, surface activity, and the ability of the macromolecules to reduce the surface tension of solvent. The values of adsorption free energy were calculated for PVP and polycomplexes. They were equal to –22.0, –23.0, and –24.8 kJ/base-mole (per one mole of PVP monomer unit) for PVP and PMAA–PVP and PAA–PVP polycomplexes, respectively.     

J Aggregation of meso-Ethylsubstituted Carbocyanine Dyes in Polymer Films

The J-aggregation capability of meso-ethylsubstituted thiacarbocyanine (Dye 1 and Dye 2) and oxacarbocyanine (Dye 3) dyes was studied in poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) films and aqueous solutions, as well as in water. In water, Dye 1 and Dye 3 form J aggregates and dimers, whereas Dye 2 occurs mainly in the dimer form. The addition of PVA to an aqueous solution leads to deaggregation of J aggregates of Dye 1 and Dye 3 and dimers of Dye 1, Dye 2, and Dye 3. Unlike PVA, PVP stimulates the J aggregation of Dye 1 in aqueous solution, with the J aggregate yield depending on the ratio between the PVP monomer unit and dye concentrations. The J aggregation of Dye 1 and Dye 3 takes place in PVA films, whereas the J aggregates of only Dye 1 are formed in PVP films. The photostability of Dye 1 J aggregates in aqueous solutions strongly depends on the spectral region of irradiation and the presence of atmospheric oxygen. The photostability is appreciably lower in aerated solutions and substantially increases in PVA films.     

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     

金属皂非水体系的研究 Ⅰ. 一元油酸钴皂有机溶液的流变性质

本文研究了一元油酸钴皂的苯与庚烷溶液的流变性质。皂溶液粘度随放置时间而增大, 并趋于稳定的平衡值。稀的钴皂溶液已经表现出显著的非牛顿性。钴皂的增稠作用是皂分子因配位结合形成大分子链的结果。添加剂含有与钴原子配位结合强的基团时, 使皂溶液粘度降至与溶剂相近。     

Controlled formation of polyamine crystalline layers on glass surfaces and successive fabrication of hierarchically structured silica thin films

The formation of silica films on the glass plate whose surface was precoated by crystalline linear poly(ethylenimine) (LPEI) in advance was systematically investigated via controlling the surface-specific crystallization of the LPEI on the glass plate. Immersing glass substrates into a hot aqueous solution of LPEI containing additives such as transition metal ions and acidic compounds and retaining them on 30 °C for desired periods resulted in the formation of crystalline LPEI layers on the substrates. Subsequently dipping this LPEI-coated glass into silica source solutions afforded successfully hierarchically structured silica film which coated continuously the surface of the substrates. In this two-step process, we found that the formation of hierarchically structured silica films strongly depended on the LPEI layer formed from the LPEI aqueous solutions containing different additives. The LPEI layer formed by changing the kinds of additives and their concentrations provides the differently structured silica films composed of turbine-like structures flatly lying-on and/or vertically standing-on as well as ribbon network structures on the surface of the substrates. Moreover, we functionalized these silica films by the introduction of hydrophobic alkyl chains or emissive Eu(III) complexes and investigated their wettability and emission properties.     

PVP/HEC分子间缔合作用机理探讨

通过粘度、紫外光谱、红外光谱和DSC谱的测定,探讨了PVP/HEC分子间的缔合机理.结果表明,PvP/HEC复合体系相对于单一体系产生了粘度的负协同效应,NaCl的加入使单一体系和复合体系的粘度均下降;在紫外可见吸收光谱中,PVP/HEC复合体系的最大吸收波长λmax相对于PVP、HEC各自的λmax都发生红移;PVP/HEC复合物的红外光谱在2370 cm-1出现新的吸收峰;DSC谱中复合物的峰温高于简单混合物,而其焓变低于简单混合物,这一切均证明HEC与PVP之间未发生疏水缔合,而是HEC的羟基与PVP的羰基之间通过氢键缔合成复合物,复合物的分子链排列较为紧密.     

Mannitol influence on the separation of DNA fragments by capillary electrophoresis in entangled polymer solutions

A new kind of sieving matrix is presented in this paper to allow satisfactory separation of DNA fragments in a relatively low viscous solution. When a certain amount of mannitol was added to cellulose solution not concentrated enough to separate PGEM-3Zf(+)/HaeIII standards well, a polymer solution with low viscosity but with very good separation effects was obtained. The separation result of this sieving buffer was comparable with those using highly concentrated cellulose solutions. The sieving ability of solutions with different cellulose concentrations and different amounts of mannitol has been investigated. It was proved that 0.5% was the minimum hydroxypropylmethylcellulose (HPMC) concentration that could be used to separate DNA fragments satisfactorily. HPMC solutions with a concentration of less than 0.5% could not separate the standard DNA fragments even in the presence of mannitol. It was found that 6% was the optimized mannitol concentration because either more or less mannitol will lead a decrease of resolution. The principle of the positive influence of mannitol has also been discussed.     

Ellipsometric study of nonionic polymer solutions

The thickness and refractive index of adsorption films of poly(vinylpyrrolidone) (PVP) and poly(ethylene glycol) (PEG) were determined by null-ellipsometry at the air-aqueous solution interface. Both parameters, in the same way as the earlier studied dynamic surface elasticity and surface tension, exhibit rather abrupt changes when the concentration approaches the range of semidilute solutions. This behavior can be explained by the worsening of the solvent quality with increasing PEG concentration and by the PVP displacement from the surface by a contamination of high surface activity.     

Viscometric study of gelatin in dilute aqueous solutions

The viscosities of aqueous solutions of gelatin at different temperatures were carefully measured in a common glass‐capillary Ubbelohde viscometer at dilute to extremely dilute concentrations. The adsorption effect that occurred in the viscosity measurements was theoretically analyzed and discussed. A theory based on Langmuir isotherms could adequately describe the existing data. Some structural information was obtained by the use of an iterative fitting procedure to treat the reduced viscosity data, which disclosed that individual gelatin chains underwent a coil‐to‐helix transition as the solution cooled from 40 to 15 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1804–1812, 2006     

甘露醇添加剂对毛细管无胶筛分电泳分离DNA的影响

在纤维素衍生物筛分体系中加入甘露醇添加剂大大提高了分离能力,在较低筛分剂浓度条件下可得到满意的分离。同时还对甘露醇影响分离的机理做出了解释。     

The Effect of Macromolecules on Foam Stability in Sodium Dodecyl Sulfate/Cetylpyridinium Bromide Mixtures

Abstract

The effects of macromolecules, gelatin, and polyvinylpyrrolidone (PVP), on the properties of foam comprising sodium dodecyl sulfate (SDS) and cetylpyridinium bromide (CPDB) have been studied by measurements of foamability, foam stability, surface tension, and solution specific viscosity. The results indicate that foamability and foam stability are significantly improved when macromolecules are added into mixed systems. Both gelatin and PVP associate with SDS/CPDB surfactants and form aggregates. Electrostatic repulsion and steric stabilization between the two sides of the foam lamellae, due to aggregation, and prevention of drainage in the lamellae, achieved by the long chains of macromolecules are the reasons for increasing foamability and foam stability. The interactions between PVP and surfactants is weaker than those between gelatin and surfactants. The strongest association between macromolecules and surfactants occurs when the molar ratio of SDS/CPDB is 1:1. By comparing PVP with gelatin, the former is favored to increase foamability, and the latter is favored to increase foam stability.     

Synthesis of palladium nanoparticles by sonochemical reduction of palladium(II) nitrate in aqueous solution

The sonochemical synthesis of stable palladium nanoparticles has been achieved by ultrasonic irradiation of palladium(II) nitrate solution. The starting solutions were prepared by the addition of different concentrations of palladium(II) nitrate in ethylene glycol and poly(vinylpyrrolidone) (PVP). The resulting mixtures were irradiated with ultrasonic 50 kHz waves in a glass vessel for 180 min. The UV-visible absorption spectroscopy and pH measurements revealed that the reduction of Pd(II) to metallic Pd has been successfully achieved and that the obtained suspensions have a long shelf life. The protective effect of PVP was studied using Fourier transform infrared (FT-IR) spectroscopy. It has been found that, in the presence of ethylene glycol, the stabilization of the nanoparticles results from the adsorption of the PVP chain on the palladium particle surface via the coordination of the PVP carbonyl group to the palladium atoms. The effect of the initial Pd(II) concentration on the Pd nanoparticle morphology has been investigated by transmission electron microscopy. It has been shown that the increase of the Pd(II)/PVP molar ratio from 0.13 x 10(-3) to 0.53 x 10(-3) decreases the number of palladium nanoparticles with a slight increase in particle size. For the highest Pd(II)/PVP value, 0.53 x 10(-3), the reduction reaction leads to the unexpected smallest nanoparticles in the form of aggregates.     

Phase transition in swollen gels 31. Swelling and mechanical behaviour of interpenetrating networks composed of poly(1-vinyl-2-pyrrolidone) and polyacrylamide in water/acetone mixtures

Swelling and mechanical behaviour of interpenetrating positively charged polymer networks (IPNs), composed of poly(1-vinyl-2-pyrrolidone) (PVP) networks and polyacrylamide (PAAm) networks, was investigated in water/acetone mixtures. The first PVP networks were prepared by radiation polymerization at room temperature; after that the PVP networks were swollen in PAAm aqueous solutions and the networks were prepared by thermal copolymerization at 65 °C. The IPNs were prepared with various amounts of the two charged comonomers (quaternary ammonium salts) in the presence of crosslinkers. Two transition regions, detected in the dependence of swelling ratio X on acetone concentration a, suggest that a two-phase structure was formed. The first transition, located between 44 and 60 vol% of acetone, corresponds to PAAm networks, while the second transition, located at 75 vol% of acetone, corresponds to PVP networks. Depending on the amount of positive charges bound to chains, both transitions exhibit continuous or discontinuous character; this fact indicates that intermolecular interactions between the two components occur with the formation of IPNs (e.g., more polar, charged PVP component increases the extent of hydrogen bonding and makes acetone less effective solvent for IPNs at the PAAm transition). The dependences of log G on log X are roughly the same regardless of charge concentrations; this means that the mechanical behaviour is predominantly determined by the degree of swelling for all gels.