Molecular composites of polyimide/poly-n-vinylpyrrolidone by in-situ polycondensation

The molecular composites of polyimide (PI) with poly-n-vinylpyrrolidone (PVP) were successfully synthesized by in-situ polycondensation of the rigid polymer in the matrix polymer solution. A strong acid-base interaction between the polyamic acid (the precursor of PI) and the PVP was confirmed experimentally. By this specific interaction the miscibility of PI with PVP was substantially improved. The PI dispersed in the PVP matrix polymer on a molecular level or nearly molecular level.     

聚酰亚胺／聚N－乙烯吡咯烷酮分子复合物的合成和表征

由原位缩聚制备了刚性高分子聚酰亚胺（ＰＩ）和柔性基体聚Ｎ－乙烯吡咯烷附（ＰＶＰ）的分子复合物，并由实验证明了中间体聚酰胺酸（ＰＡ）和聚乙烯吡咯烷酮大分子之间存在的酸一碱相互作用．这种相互作用促进了混容性，使聚酰亚胺能以分子水平或接近分子水平分散在聚毗咯烷酮的基体之中．聚酰亚胺／聚Ｎ－乙烯吡咯烷团分子复合物的薄膜呈透明性，在整个组成范围内只有一个Ｔｇ，显示单相行为。当ＰＩ含量＜２０％时，ＳＥＭ相片呈现均相形貌，看不到ＰＩ微晶．广角Ｘ－ｒａｙ衍射图表明ＰＩ特征结晶峰消失，和无定形的ＰＶＰ完全混容．当ＰＩ含量＞４０％，ＳＥＭ显示有均匀分布的、棒状ＰＩ微晶存在．通过分子复合，即使ＰＩ含量为１０％，聚Ｎ－乙烯吡咯烷酮不再溶于乙醇，耐热性也有提高．     

聚酰亚胺／聚N－乙烯吡咯烷酮分子复合物的合成和表征

由原位缩聚制备了刚性高分子聚酰亚胺（ＰＩ）和柔性基体聚Ｎ－乙烯吡咯烷附（ＰＶＰ）的分子复合物，并由实验证明了中间体聚酰胺酸（ＰＡ）和聚乙烯吡咯烷酮大分子之间存在的酸一碱相互作用．这种相互作用促进了混容性，使聚酰亚胺能以分子水平或接近分子水平分散在聚毗咯烷酮的基体之中．聚酰亚胺／聚Ｎ－乙烯吡咯烷团分子复合物的薄膜呈透明性，在整个组成范围内只有一个Ｔｇ，显示单相行为。当ＰＩ含量＜２０％时，ＳＥＭ相片呈现均相形貌，看不到ＰＩ微晶．广角Ｘ－ｒａｙ衍射图表明ＰＩ特征结晶峰消失，和无定形的ＰＶＰ完全混容．当ＰＩ含量＞４０％，ＳＥＭ显示有均匀分布的、棒状ＰＩ微晶存在．通过分子复合，即使ＰＩ含量为１０％，聚Ｎ－乙烯吡咯烷酮不再溶于乙醇，耐热性也有提高．     

Structural changes of silver polymer electrolytes: Comparison between poly(2‐ethyl‐2‐oxazoline) and poly(N‐vinyl pyrrolidone) complexes with silver salt

The difference between the polymer matrices of poly(2‐ethyl‐2‐oxazoline) (POZ) and poly(N‐vinyl pyrrolidone) (PVP) does not have a significant effect on the facilitated propylene transport and propylene solubility in 1:1 polymer/silver salt complex membranes, according to our previous work. In this article, its origin is investigated in terms of both microstructures of silver polymer electrolytes and the coordinative interaction of silver ion with polymer and with the counteranion. Initially different microstructures of POZ and PVP become similar to each other upon dissolving a large amount of silver salt, as evidenced by propane transport properties, specific volume, and Bragg d‐spacing. The dissolution of the silver salt in the polymer solvent strongly depends on the coordinative interaction between silver ion and carbonyl oxygen of POZ and PVP. Thus, the structural similarity upon dissolving silver salts in POZ and PVP is primarily determined by the coordinative interaction between silver ion and carbonyl oxygen, which was confirmed by theoretical structure calculation based on density functional theory and by IR and Raman spectroscopy. Therefore, facilitated olefin transport for silver polymer electrolyte membranes does not strongly depend on the polymeric matrix at high silver concentrations. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 232–237, 2004     

Lithium ion conduction and ion-polymer interaction in poly（vinyl pyrrolidone） based electrolytes blended with different plasticizers

Poly（ethylene oxide）, poly（vinyl pyrrolidone）（PEO/PVP）, lithium perchlorate salt（Li Cl O4） and different plasticizer based, gel polymer electrolytes were prepared by the solvent casting technique. XRD results show that the crystallinity decreases with the addition of different plasticizers. Consequently, there is an enhancement in the amorphousity of the samples responsible for the process of ion transport. FTIR spectroscopy is used to characterize the structure of the polymer and confirms the complexation of plasticizer with host polymer matrix. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. Among the various plasticizers, the ethylene carbonate（EC） based complex exhibits a maximum ionic conductivity value of the order of2.7279 10 4S cm 1. Thermal stability of the prepared electrolyte films shows that they can be used in batteries at elevated temperatures. PEO（72%）/PVP（8%）/Li Cl O4（8%）/EC（12%） has the maximum ionic conductivity value which is supported by the lowest optical band gap and lowest intensity in photoluminescence spectroscopy near 400–450 nm. Two and three dimensional topographic images of the sample having a maximum ionic conductivity show the presence of micropores.     

On-channel base stacking in microchip capillary gel electrophoresis for high-sensitivity DNA fragment analysis

We evaluated a novel strategy for high-sensitivity DNA fragment analysis in a conventional glass double-T microfluidic chip. The microchip allows for a DNA on-channel concentration based on base stacking (BS) with a microchip capillary gel electrophoretic (MCGE) separation step in a poly(vinylpyrrolidone) (PVP) sieving matrix. Depending if low conductivity caused a neutralization reaction between the hydroxide ions and the run buffer component Tris+, the stacking of DNA fragments were processed in the microchip. Compared to a conventional MCGE separation with a normal electrokinetic injection, the peak heights of 50-2650-base pair (bp) DNA fragments on the MCGE-BS separation were increased 3.9-8.0-fold. When we applied the MCGE-BS method to the analysis of a clinical sample of bovine theileria after PCR reaction, the peak height intensity of the amplified 816-bp DNA fragment from the 18S rRNA of T. buffeli was enhanced 7.0-fold compared to that of the normal injection method.     

Separation of double-stranded DNA fragments by capillary electrophoresis using polyvinylpyrrolidone and poly(N,N-dimethylacrylamide) transient interpenetrating network

A noncross-linked interpenetrating polymer network (IPN), consisting of poly(N,N-dimethylacrylamide) (PDMA) and polyvinylpyrrolidone (PVP, weight-average molecular weight M(w) = 1 x 10(6) g/mol) was synthesized by polymerizing N,N-dimethylacrylamide (DMA) monomers directly in PVP buffer solution and tested as a separation medium for double-stranded (ds)DNA analysis without further purification. Due to the incompatibility of PVP and PDMA, a simple solution mixture could incur a microphase separation and showed poor performance on dsDNA separation. However, a dramatic improvement was achieved by the formation of an IPN. We attributed the high sieving ability of IPN as due to an increase in the number of entanglements by the more extended polymer chains. Apparent viscosity studies showed that the IPN had a much higher viscosity than the simple mixture containing the same amount of PDMA and PVP. In 1 x Tris-borate-EDTA (TBE) buffer, the concentration ratio of PDMA and PVP had a great effect on the DNA separation. At optimal conditions, the 22 fragments in pBR322/HaeIII DNA were successfully separated within 15 min, with a resolution of better than 1.0 for 123/124 bp.     

Hydrogel characteristics of electron-beam-immobilized poly(vinylpyrrolidone) films on poly(ethylene terephthalate) supports

A novel strategy for the preparation of thin hydrogel coatings on top of polymer bulk materials was elaborated for the example of poly(ethylene terephthalate) (PET) surfaces layered with poly(vinylpyrrolidone) (PVP). PVP layers were deposited on PET foils or SiO2 surfaces (silicon wafer or glass coverslips) precoated with PET and subsequently cross-linked by electron beam treatment. The obtained films were characterized by ellipsometry, X-ray photoelectron spectroscopy, infrared spectroscopy in attenuated total reflection, atomic force microscopy (AFM), and electrokinetic measurements. Ellipsometric experiments and AFM force-distance measurements showed that the cross-linked layers swell in aqueous solutions by a factor of about 7. Electrokinetic experiments indicated a strong hydrodynamic shielding of the charge of the underlying PET layer by the hydrogel coatings and further proved that the swollen films were stable against shear stress and variation of pH. In conclusion, electron beam cross-linking ofpreadsorbed hydrophilic polymers permits a durable fixation of swellable polymer networks on polymer supports which can be adapted to materials in a wide variety of shapes.     

Poly-N-hydroxyethylacrylamide (polyDuramide): a novel,hydrophilic, self-coating polymer matrix for DNA sequencing by capillary electrophoresis

A replaceable polymer matrix, based on the novel monomer N-hydroxyethylacrylamide (HEA), has been synthesized for application in DNA separation by microchannel electrophoresis. The monomer was found by micellar electrokinetic chromatography analysis of monomer partitioning between water and 1-octanol to be more hydrophilic than acrylamide and N,N-dimethylacrylamide. Polymers were synthesized by free radical polymerization in aqueous solution. The weight-average molar mass of purified polymer was characterized by tandem gel permeation chromatography-multiangle laser light scattering. The steady-shear rheological behavior of the novel DNA sequencing matrix was also characterized, and it was found that the viscosity of the novel matrix decreases by more than 2 orders of magnitude as the shear rate is increased from 0.1 to 1000 s(-1). Moreover, in the shear-thinning region, the rate of change of matrix viscosity with shear rate increases with increasing polymer concentration. Poly-N-hydroxyethylacrylamide (PHEA) exhibits good capillary-coating ability, via adsorption from aqueous solution, efficiently suppressing electroosmotic flow (EOF) in a manner comparable to that of poly-N,N-dimethylacrylamide. Under DNA sequencing conditions, adsorptive PHEA coatings proved to be stable and to maintain negligible EOF for over 600 h of electrophoresis. Resolution of DNA sequencing fragments, particularly fragments > 500 bases, in PHEA matrices generally improves with increasing polymer concentration and decreasing electric field strength. When PHEA is used both as a separation matrix and as a dynamic coating in bare silica capillaries, the matrix can resolve over 620 bases of contiguous DNA sequence within 3 h. These results demonstrate the good potential of PHEA matrices for high-throughput DNA analysis by microchannel electrophoresis.     

Nanocomposite membranes containing positively polarized gold nanoparticles for facilitated olefin transport

Positively polarized gold nanoparticles have been demonstrated for use as stable olefin carriers for facilitated olefin transport membranes. The formation and size of gold nanoparticles stabilized by 4-dimethylaminopyridine (DMAP) were monitored using X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–visible spectroscopy. Nanocomposite membranes that deliver high separation performance for olefin/paraffin mixtures were prepared by dispersing gold nanoparticles stabilized by DMAP in a polymer matrix, poly(vinyl pyrrolidone) (PVP). X-ray photoelectron spectroscopy (XPS) and zeta potential measurements revealed that gold nanoparticles stabilized by DMAP exhibited a high positive polarity, which is responsible for the reversible interaction between the gold nanoparticles and olefin molecules. Compared to neat PVP membranes, the composite membranes consisting of PVP and the polarized gold nanoparticles showed stable and enhanced separation of olefin/paraffin mixtures.     

Further Study on Separation of DNA Fragments by Capillary Electrophoresis by Quasi-interpenetrating Network of Polyacryamide and Polyvinylpyrrolidone with UV Detection

Quasi-interpenetrating network of polyacrylamide （PAA） and polyvinylpyrrolidone （PVP） had been successfully used for single-base resolution of double-stranded DNA （0.76 for 123 bp/124 bp） and single-stranded DNA fragments （0.97 for 123 b/124 b） with UV detection. This quasi-IPN （interpenetrating network） sieving matrix showed low viscosity （23.5 mPa·s at 25 ℃） and decreased with increasing temperature. This polymer also exhibited dynamically coating capacity and could be used in the uncoated capillary. The effects of temperature and electric field strength on the DNA separation of quasi-IPN matrix were also investigated and found that the temperature and electric field strength could markedly affected the mobility behavior of DNA fragments. This polymer matrix has also applied to separate the bigger DNA fragments by capillary electrophoresis with UV detection. Under the denaturing conditions, this matrix separated the samples with last fragment of 1353 base in 40 rain, in which the doublet of 309/310 base was partial separated and the resolution was 0.88.     

Influence of a cellulose diacetate matrix on the complexation kinetics of tetraphenylporphin with Zn and Cd

The dependence of the reaction rate of tetraphenylporphin zinc and cadmium complexes in a polymer matrix on a base of cellulose diacetate and low-molecular model solutions was investigated. The characteristics of the diffusive transport of aqueous solutions of zinc and cadmium acetates through the cellulose diacetate membrane were obtained. The kinetic control of the porphyrin reaction incorporated into the polymer, and the determining influence of the steric limitations of the matrix of a rigid chain polymer on macroheterocycle deformation (and thus its reactivity) are shown.     

Charge transport and contact resistance in coplanar devices based on colloidal polyaniline dispersion

The charge transport properties of thin films prepared from colloidal dispersion of polyaniline stabilized by poly(N‐vinylpyrrolidone) (PANI/PVP) have been investigated. The electrical characterization of coplanar device comprising of gold electrodes and PANI/PVP film deposited by spin coating served to gain insights into the contact and bulk resistance. The films prepared from PANI/PVP colloidal dispersion show high stability over a large temperature range. Temperature dependent measurements in the range from 90 to 350 K reveal that the charge transport can be described by a three‐dimensional variable‐range hopping mechanism as the dominant mode in the films. The stability of the films cast from dispersion within a large temperature range opens the possibility of the application as a polymer semiconductor layer in sensors and charge‐transport interlayer in organic solar cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1710–1716     

Direct electrochemiluminescence detection of oxidized DNA in ultrathin films containing [Os(bpy)2(PVP)10]2+

Direct electrochemiluminescence (ECL) involving oxidized DNA was demonstrated in ultrathin films of cationic polymer [Os(bpy)2(PVP)10]2+ [PVP = poly(vinyl pyridine)] assembled layer-by-layer with DNA or oligonucleotides. Electrochemically oxidized Os(II) sites generated ECL from films containing oxo-guanines on DNA formed by chemical oxidation using Fenton reagent. Films combining DNA, [Ru(bpy)2(PVP)10]2+, and [Os(bpy)2(PVP)10]2+ had Os(II) sites that produced ECL specific for oxidized DNA, and Ru(II) sites gave ECL from reaction with oxo-adenines, chemically damaged DNA, and possibly from cleaved DNA strands.     

Polyvinylpyrrolidone adsorption and structural studies on homoionic Li-, Na-, K-, and Cs-montmorillonite colloidal suspensions

Structural aspects of dilute homoionic Li-, Na-, K-, and Cs-montmorillonite (M-montmorillonite) particle suspension (1 g/L) under low-electrolyte-concentration (0.1 mM MCl) conditions were characterized by static (absorbance or turbidity) and dynamic (photon correlation spectroscopy) light-scattering methods as well as by the adsorption behaviors of nonionic polyvinylpyrrolidone (PVP) mol wt 5,000 g/mol (LMW PVP) and mol wt 400,000 g/mol (HMW PVP). Taking Li-montmorillonite as a reference for a single plate particle, a particle size increase and a surface accessibility decrease to polymer adsorptions were measured along the Li, Na, K, and Cs series. The results are related to the existence of montmorillonite quasicrystals or tactoids in diluted suspension, whose stability increases along the same cation series. Molecular weight effects on the PVP surface accessibility are discussed in terms of permeation properties of the different M-montmorillonite particles. Modeling the results calculates an average number of plates in montmorillonite quasi-crystals and the surface area distribution of ultramicropores <0.7 nm and pores >0.7 nm in M-montmorillonite particles. It can also be demonstrated by applying hydrodynamic and electrokinetic methods that the measured high absorbance or turbidity increase of PVP-loaded montmorillonite particles is not due to aggregation phenomena but to a PVP contribution in the light-scattering intensity.     

Silver nanoparticles stabilized by crosslinked poly(vinyl pyrrolidone) and its application for facilitated olefin transport

Positively polarized silver nanoparticles by poly(vinyl pyrrolidone) (PVP) have been demonstrated for use as stable olefin carriers for facilitated olefin transport membranes. The formation and size of silver nanoparticles stabilized by PVP were monitored using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Nanocomposite membranes consisting of polymer and silver nanoparticles stabilized by PVP exhibited the high separation performance for olefin/paraffin mixtures. X-ray photoelectron spectroscopy (XPS) showed that silver nanoparticles stabilized by PVP exhibited a high positive polarity, resulting in the reversible interaction between the surface of silver nanoparticles and olefin molecules.     

Separation of double-stranded DNA fragments by capillary electrophoresis in interpenetrating networks of polyacrylamide and polyvinylpyrrolidone

Mixtures of two polymers with totally different chemical structures, polyacrylamide and polyvinylpyrrolidone (PVP) have been successfully used for double-stranded DNA separation. By polymerization of acrylamide in a matrix of PVP solution, the incompatibility of these two polymers was suppressed. Laser light scattering (LLS) studies showed that highly entangled interpenetrating networks were formed in the solution. Further systematic investigation showed that double-stranded DNA separation was very good in these interpenetrating networks. With a concentration combination of as low as 2% w/v PVP (weight-average molecular mass Mr = 1 x 10(6) g/mol) + 1% w/v polyacrylamide (Mr = 4 x 10(5) g/mol), the 22 fragments in pBR322/HaeIII DNA, including the doublet of 123/124 bp, have been successfully separated within 6.5 min. Under the same separation conditions, similar resolution could only be achieved by using polyacrylamide (Mr = 4 x 10(5) g/mol) with concentrations higher than 6% w/v and could not be achieved by using only PVP (Mr = 1 x 10(6) g/mol) with a concentration as high as 15% w/v. It is noted that the interpenetrating network formed by 2% PVP and 1% polyacrylamide has a very low viscosity and can dynamically coat the inner wall of a fused-silica capillary. The separation reached an efficiency of more than 10(7) theoretical plate numbers/m and a reproducibility of less than 1% relative standard deviation of migration time in a total of seven runs. The interpenetrating network could stabilize polymer chain entanglements. Consequently, the separation speed was increased while retaining resolution.     

Mechanical properties of molecular composites. I. Poly (p‐phenylene terephthalamide) anion molecules dispersed in poly(4‐vinylpyridine)

Molecular composites have been prepared by dispersing rigid‐rod molecules of ionically‐modified poly(p‐phenylene terephthalamide) (PPTA anion) in a polar poly(4‐vinylpyridine) (PVP) matrix. For concentrations up to 5 wt % of the rigid‐rod reinforcement, the resulting composites are transparent and possess a single glass transition temperature that increases with concentration of the PPTA anion. The mechanical properties of the molecular composites are found to increase with concentration and to attain maximum values at about 5 wt % of the PPTA anion. The enhancement in properties, and the miscibility induced between the two component polymers, is attributed to the development of specific interactions between the ionic groups of the PPTA anion and the polar units of the PVP matrix. When such interactions are not present, as in composites reinforced with non‐ionic PPTA, the samples are opaque and their properties are significantly reduced compared to those of the PPTA anion/PVP composites. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2201–2209, 1999     

Evaluation of different nucleic acid stains for sensitive double-stranded DNA analysis with capillary electrophoretic separation

This paper outlines the first use of SYTOX Orange, SYTO 82 and SYTO 25 nucleic acid stains for on-column staining of double-stranded DNA (dsDNA) fragments separated by capillary electrophoresis (CE). Low-viscosity, replaceable poly(vinylpyrrolidone) (PVP) polymer solution was used as the sieving matrix on an uncoated fused-silica capillary. The effects of PVP concentration, electric field strength, and incorporated nucleic acid stain concentrations on separation efficiency were examined for a wide range of DNA fragment sizes. Our study was focused on using nucleic acid stains efficiently excitable at a wavelength of 532 nm. Among the five tested nucleic acid stains, SYTOX Orange stain was shown to have the best sensitivity for dsDNA detection by CE. About a 500-fold lower detection limit was obtained compared to commonly used ethidium bromide and propidium iodide. SYTOX Orange stain also provided a wide linear dynamic range for direct DNA quantitation with on-line CE detection. Use of SYTOX Orange stain can greatly improve the measurement of DNA fragments by CE, which will enable an expanded set of applications in genomics and diagnostics.     

Polycationic graft copolymers of poly(N-vinylpyrrolidone) as non-viral vectors for gene transfection

Novel graft copolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) with N-vinylpyrrolidone (NVP) were designed and synthesized by the free radical copolymerization of DMAEMA with precursor polymers of vinyl-functionalized poly(N-vinylpyrrolidone) (PVP). The ability of the PVP- grafted copolymers to bind and condense DNA was confirmed by ethidium bromide displacement assay, agarose gel electrophoresis and transmission electron microscopy. The presence of PVP in the copolymers had a favorable effect on the biophysical properties of polymer/DNA complexes. Colloidal stable complexes obtained from the copolymer systems, were shown to be separate, uniformly spherical nanoparticles by transmission electron microscopy. The approximate diameter of the complexes was 150–200 nm, as determined by dynamic light scattering studies. These results confirm an important role played by the PVP grafts in producing compact stable DNA complexes. The ζ-potential measurements revealed that the incorporation of the PVP grafts reduced the positive surface charge of polymer/DNA complexes. The cytotoxicity of the copolymers decreased with an increasing fraction of PVP. Furthermore, in vitro transfection experiments with these copolymers showed improved ability of transfection in cell culture, demonstrating an important role for PVP grafts in enhancement of the transfection efficiency.