Epoxy resin cured with poly(4-vinyl pyridine)

Poly(4-vinylpyridine) (P4VP) was used as the macromolecular curing agent to prepare epoxy networks. The crosslinking structures were investigated by means of Fourier transform infrared spectroscopy (FTIR). It is identified that depending on the ratios of DGEBA to P4VP, different reactions dominated the formation of the crosslinking networks, which were involved the formation of pyridone (or cyclic amide) resulting from epoxide groups of DGEBA and pyridine rings of P4VP, the Diels-Alder reaction of in situ formed conjugated 3,5-diene in a 6-member ring and the homopolymerization of DGEBA initiated by pyridine moiety of P4VP. Differential scanning calorimetry (DSC) showed that all the DGEBA-P4VP co-crosslinked thermosets displayed single glass transition temperature (T_g), suggesting that the crosslinked networks are homogenous. In addition, it is noted that the T_g's of the DGEBA-rich network are greatly dependent on the molecular weight of P4VP used.     

Sorption of phenolics onto cross-linked poly(4-vinyl pyridine)

In order to explore the possibility of using cross-linked polymer of 4-vinyl pyridine as sorbent for removal, separation and recovery of phenolic species, the sorption behaviour of a number of model phenolic compounds, differing from each other in acidity and molecular size, has been studied, using the vinyl pyridine polymer both in the free-base form and in salt form. The phenolic compounds used include phenol, p-cresol, p-chlorophenol, p-nitrophenol, m-aminophenol, polyphenol and lignin. The sorption of phenolic compounds with the free-base resin affords significantly greater sorption capacity than that with the same resin used in the salt form. The level of pH of the aqueous medium has a marked influence on the sorption of phenols by free-base PVP, the maximum sorption taking place at lower pH for more acidic phenols, which is in accord with the hydrogen bonding mechanism of phenolics sorption. The Freundlich isotherm equation provides an adequate fit to the sorption data, while the coefficient of the isotherm equation bears a distinct relationship to the acidity of the phenolic sorbate. A simplified rate equation based on the concept of linear driving force fitted the initial sorption rate data well, yielding a value for the particle-diffusion control rate coefficient for each phenolic species. Substituted phenols have lower intraparticle diffusivities than phenol, with the diffusivity decreasing as the size of the substituent group increases. Lignin undergoes much stronger interaction with the resin than do the other phenols. Consequently, while the sorbed phenols are all easily eluted by dilute alkali, lignin sorbed onto the resin is however removed only with considerable difficulty.     

Tuning anti-microbial activity of poly(4-vinyl 2-hydroxyethyl pyridinium) chloride by anion exchange reactions

A series of new bioactive polymers with pendant choline analogous group was prepared by anion exchange reaction direct at the quaternary nitrogen of the polycation. Poly(4-vinyl 2-hydroxyethyl pyridinium) chloride was prepared in situ by simultaneous polymerization and quaternization of 4-vinyl pyridine with 2-chloroethanol that also acts as catalyst. The counter anion (Cl⁻) of the polycation was exchanged by anion exchange reaction with Br⁻, ⁻OH, ⁻SH, NO₃ ⁻, BF₄ ⁻ or CF₃COO⁻. Evidence of anion exchange was obtained by the characterization of the resultant polymers. The nature of the counter anion has profound effect on their properties including strong anion-dependent anti-microbial activity against bacteria and fungus. Polymer containing ⁻OH was observed to be the most potent anti-microbial agent with the lowest minimum inhibitory concentration against both the classes of microbes studied.     

Studies on transparent and solid proton conductors based on NH4H2PO4 doped poly(vinyl alcohol)

A novel transparent and anhydrous proton conductor, which can be used in solid electrochromic device (ECD), was prepared by mixing poly(vinyl alcohol) (PVA) with ammonium dihydrogen phosphate (NH₄H₂PO₄). X-ray diffraction, differential scanning calorimeter (DSC), and Infrared spectra were used to characterize the structure of PVA/xNH₄H₂PO₄ composite membrane. Proton conductivity of the composite membranes was studied by the complex impedance method. The proton conductivity of the composite membranes increases with increasing temperature and increases with increasing phosphate doping-level at first and then decreases with increasing phosphate content after a certain value of x. The highest proton conductivity is near the area of x = 0.067. The transmittance of the complex membranes always decreases with increasing doping level of phosphate.     

Synthesis of Cr(VI)-imprinted poly(4-vinyl pyridine-co-hydroxyethyl methacrylate) particles: its adsorption propensity to Cr(VI)

The aim of this study is to prepare ion-imprinted polymers, which can be used for the selective removal of Cr(VI) anions from aqueous media. 4-Vinyl pyridine (4-VP) was used as functional monomer. The Cr(VI)-imprinted poly(4-vinyl pyridine-co-2-hydroxyethyl methacrylate), poly(VP-HEMA), particles were prepared by bulk polymerization. The Cr(VI)-imprinted polymer particles were grained from the bulk polymer, and the template ions (i.e., Cr(VI)) were removed using thiourea (0.5%, v/v) in 0.5M HCl. The Cr(VI)-imprinted polymer contained 21.4 μmol 4-VP/g polymers. The specific surface area of the IIP2 particles was found to be 34.5m(2)/g (size range of 75-150 μm), and the swelling ratio was about to 108%. The effect of initial concentration of Cr(VI) anions, the adsorption rate and the pH of the medium on adsorption capacity of Cr(VI)-imprinting polymer were studied. The maximum experimental adsorption capacity was 3.31 mmol Cr(VI)/g polymer. Under competitive condition, the adsorption capacity of Cr(VI)-imprinted particles for Cr(VI) is 13.8 and 11.7 folds greater than that of the Cr(III) and Ni(II) ions, respectively. The first- and second order kinetics models were estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. The Langmuir adsorption isotherm model was well described the Cr(VI)-imprinted system and the maximum adsorption capacity (Q(max)) was found to be 3.42 mmol/g. Moreover, the reusability of the poly(VP-HEMA) particles was tested for several times and no significant loss in adsorption capacity was observed.     

Biocompatibility of solid poly (ortho ester)

In previous studies poly (ortho ester) (POE) has shown promise as a resorbable device, a hemostatic sealant and as a carrier for drugs in bone surgery. The aim of this study was to evaluate the tissue reactions of solid poly (ortho ester) implanted into both tibiae of 17 rabbits. One half of the rods were sterilized by gamma radiation and the other half by ethylene oxide. The follow-up times were from 1 week to 21 weeks, after which the animals were killed and the bony specimens examined histologically. The connective tissue samples were examined immunohistochemically in order to study the occurrences of two extracellular matrix glycoproteins, tenascin and fibronectin. The results showed that solid poly (ortho ester)s induce a moderate inflammatory reaction for 9 weeks. Tenascin and fibronectin were present in samples from 1 week up to 4 weeks. It was also found that gamma sterilized POE was resorbed at week 7 and ethylene oxide sterilized POE at week 13.     

In situ Raman monitoring of competitive adsorption of Ag and Au nanoparticles onto a poly(4-vinyl pyridine) surface

The competitive adsorption of citrate-capped Ag and Au nanoparticles (~25 nm in diameter) onto a poly(4-vinyl pyridine) (P4VP) surface has been investigated by means of Raman scattering spectroscopy. The P4VP film prepared on a glass slide was too thin for its normal Raman spectrum to be observed, but the Raman peaks of P4VP could be detected upon the adsorption of Ag and/or Au nanoparticles onto the film, due to the surface-enhanced Raman scattering (SERS) effect associated with the localized surface plasmon of Ag and/or Au nanoparticles. Neither quartz crystal microbalance nor atomic force microscopy (AFM) nor scanning electron microscopy (SEM) methodologies can distinguish between Ag and Au nanoparticles during their adsorption onto P4VP, but it is possible through Raman scattering spectroscopy because Ag (though not Au) nanoaggregates are SERS active at 514.5 nm excitation, while both Ag and Au nanoaggregates are SERS active at 632.8 nm excitation. Coupled with the AFM data, we were thus able to infer that about 120 Ag nanoparticles per 1 μm(2) were adsorbed, along with 60 Au nanoparticles per 1 μm(2), onto the P4VP film over a period of 1.5 h from a 1 : 1 mixture of Ag and Au sols at 1.6 nM each.     

锂离子电池用固态偏氟乙烯-六氟丙烯共聚物电解质的研究进展

固体聚合物电解质具有质轻、安全、易加工等优点,在锂离子电池中具有极大的应用价值.综述了以偏氟乙烯-六氟丙烯(PVDF-HFP)共聚物为基的聚合物电解质的研究工作,介绍了PVDF-HFP固体电解质的制备方法,分析了影响此聚合物电解质性能的因素,并讨论了PVDF-HFP电解质的改性措施,对今后的发展方向作了简要展望.     

Polymeric nanomedicines based on poly(lactide) and poly(lactide-co-glycolide)

Small molecule chemotherapeutics often have undesired physiochemical and pharmacological properties, such as low solubility, severe side effect and narrow therapeutic index. To address these challenges, polymeric nanomedicine drug delivery technology has been routinely employed, in particular with the use of biodegradable and biocompatible polyesters, such as poly(lactide) (PLA) and poly(lactide-co-glycolide) (PLGA). Here we review the development and use of PLA and PLGA for the delivery of chemotherapeutic agents in the forms of polymer–drug conjugates and nanoconjugates.     

Encapsulation of magnetic nanoparticles in a pH-sensitive poly(4-vinyl pyridine) polymer: a step forward to a multi-responsive system

A multiresponsive system that consists on pH-responsive polymer microspheres with encapsulated iron oxide magnetic nanoparticles that rendered the core magnetic to enable externally controlled actuation under magnetic induction has been developed. The inorganic nanoparticles were first prepared and, then, further encapsulated in a pH-sensitive poly(4-vinylpyridine). These spheres have been obtained by a modification of the simple, rapid and high-reproducible nanoprecipitation method. Magnetic measurements showed that the iron oxide nanoparticles are superparamagnetic and, therefore, able to undergo a local increase of the temperature when an oscillating magnetic field is applied. Magnetically triggered heating and pH sensitivity can be useful for biomedical applications.     

Synthesis of polystyrene,poly(styrene/4-vinylpyridine), poly(p-nitrostyrene) and poly(p-aminostyrene)-coated silica and their extraction capabilities for amphetamine

Several novel organic–inorganic hybrid materials, including polystyrene-coated silica (SG-PS), poly(styrene/4-vinylpyridine)-coated silica (SG-PVP), poly(p-nitrostyrene)-coated silica (SG-PS-NO₂) and poly(p-aminostyrene)-coated silica (SG-PS-NH₂), were synthesized in order to improve the extraction methods of harmful stimulants via solid phase extraction. The materials were characterized using infrared spectra (IR), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET) surface area measurement and thermogravimetric analysis (TG). The application of the new materials in solid phase extraction columns to extract methamphetamine revealed that the extraction capability of poly(styrene/4-vinylpyridine)-coated silica is the best among the four materials, which provides novel supporter materials for extracting amphetamine-derived drugs.     

Facile synthesis of thick films of poly(methyl methacrylate), poly(styrene), and poly(vinyl pyridine) from Au surfaces

Atom transfer radical polymerization (ATRP) is commonly used to grow polymer brushes from Au surfaces, but the resulting film thicknesses are usually significantly less than with ATRP from SiO(2) substrates. On Au, growth of poly(methyl methacrylate) (PMMA) blocks from poly(tert-butyl acrylate) brushes occurs more rapidly than growth of PMMA from initiator monolayers, suggesting that the disparity between growth rates from Au and SiO(2) stems from the Au surface. Radical quenching by electron transfer from Au is probably not the termination mechanism because polymerization from thin, cross-linked initiators gives film thicknesses that are essentially the same as the thicknesses of films grown from SiO(2) under the same polymerization conditions. However, this result is consistent with termination through desorption of thiols from noncross-linked films, and reaction of these thiols with growing polymer chains. The enhanced stability of cross-linked initiators allows ATRP at temperatures up to ～100 °C and enables the growth of thick films of PMMA (350 nm), polystyrene (120 nm) and poly(vinyl pyridine) (200 nm) from Au surfaces in 1 h. At temperatures >100 °C, the polymer brush layers delaminate as large area films.     

Performance and stability of electroluminescent device with self-assembled layers of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) and polyelectrolytes

Self-assembled poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT) layers were prepared on polyelectrolytes multilayers (polyethylenimine and polyacrylic acid) on an indium–tin oxide (ITO) surface using a layer-by-layer technique. The electroluminescence efficiencies of the devices were drastically enhanced by the addition of self-assembled PEDOT layers between the spin-coated PEDOT and ITO. The ITO corrosion by the acidic PEDOT and the migration of the indium components across the interfacial layers were inhibited in the presence of the polyelectrolyte multilayers. Remarkably, the lifetime of the device was 60% longer than the one without the self-assemblies, which was attributed to the improvement in the interfacial contact.     

聚乙烯醇/钴盐共混膜结构及其对环己烯-环己烷吸附性能研究

采用PVA分别与硝酸钴(Co(NO3)2)、氯化钴(CoCl2)和醋酸钴(Co(CH3COO)2)共混制成均相膜．X-射线衍射研究表明：Co(NO3)2,CoCl2和Co(CH3COO)2能很好地溶于PVA中,且PVA膜中引入钴盐后,结晶度明显下降．通过对环己烯、环己烷溶胀实验发现,3种膜均对环己烯优先吸附,其中PVA／Co(CH3COO)2膜对环己烯优先吸附性能最好,而且环己烯在膜中的扩散也最快达到平衡．     

Fabrication of 3D interconnected porous TiO2 nanotubes templated by poly(vinyl chloride-g-4-vinyl pyridine) for dye-sensitized solar cells

Porous TiO(2) nanotube arrays with three-dimensional (3D) interconnectivity were prepared using a sol-gel process assisted by poly(vinyl chloride-graft-4-vinyl pyridine), PVC-g-P4VP graft copolymer and a ZnO nanorod template. A 7 μm long ZnO nanorod array was grown from the fluorine-doped tin oxide (FTO) glass via a liquid phase deposition method. The TiO(2) sol-gel solution templated by the PVC-g-P4VP graft copolymer produced a random 3D interconnection between the adjacent ZnO nanorods during spin coating. Upon etching of ZnO, TiO(2) nanotubes consisting of 10-15 nm nanoparticles were generated, as confirmed by wide-angle x-ray scattering (WAXS), energy-filtering transmission electron microscopy (EF-TEM) and field-emission scanning electron microscopy (FE-SEM). The ordered and interconnected nanotube architecture showed an enhanced light scattering effect and increased penetration of polymer electrolytes in dye-sensitized solar cells (DSSC). The energy conversion efficiency reached 1.82% for liquid electrolyte, and 1.46% for low molecular weight (M(w)) and 0.74% for high M(w) polymer electrolytes.     

Structural properties of silver particulate films deposited on softened polymer blends of polystyrene/poly (2-vinyl pyridine)

Results of the structural studies of silver particulate films deposited at a rate of 0.4 nm/s on polymeric blends of polystyrene/poly (2-vinyl pyridine), PS/P2VP held at a temperature 457 K by evaporation in a vacuum of 8 × 10⁻⁶ Torr are reported here. The morphology of silver particulate films, characterized by their size, size distribution, shape and inter-particle separation, was observed to modify due to blending of PS with P2VP and amount of silver deposited. The red shift in the plasmon resonance indicates the effect of blending P2VP with PS. Scanning electron microscopy was used to study the change in morphology of the silver nanoparticles in correlation with the optical properties of silver particulate films on PS/P2VP blends. The silver nanoparticles on the thin layers of polymer blends exhibited much smaller, narrower dispersion and wide size distribution due to blending of PS with P2VP.     

Synthesis and characterization of conducting poly (1-aminonaphthalene), poly (2-aminonaphthalene) and poly (aniline-co-1-aminonaphthalene)

Poly (1&2)-aminonaphthalene and poly (aniline-co-1-aminonaphthalene) have been synthesized in high yields by chemical oxidative polymerization method. The polymers are soluble in polar solvents such as DMSO, NMP etc. In PNA-2 as head-to-tail coupling cannot occur, the electrical conductivity is lower than PNA-1. The copolymer exhibits distinct morphology, higher viscosity, characteristic exciton peak, appreciable thermal stability and electrical conductivity compared to PNA-1.     

Comparative study on poly(3-alkylpyrroles)

Polypyrrole(PPY), poly(3-methylpyrrole)(PMPY) and poly(3-octylpyrrole) (POCPY) were prepared under the same electrochemical polymerization conditions and their properties were comparatively studied. Electrical conductivity increased in the order POCPY < PMPY < PPY. Absorption spectra measuredin situ showed that while peak energy of the interband transition increased in the order PPY < PMPY < POCPY, the absorption edge of PPY was located at almost equal energy as that of PMPY and POCPY. Stability, indicated by decrease in the ratio of conductivities after storage to the initial conductivity, was primarily dependent on the length of alkyl chains, secondly on dopants and associated with spectral deterioration. While the initial conductivity was strongly dependent on temperature and current density during electrochemical polymerization, the stability was virtually independent of these conditions. The stability increased in the order: POCPY < PMPY < PPY. Spectral change during storage in air was dependent on the chemical structure of polymers but almost independent of dopants. The spectral change indicated PPY to be in nearly initial states after 10 days and POCPY to be in almost completely undoped states after 200 days. In cyclic voltammograms, PPY and POCPY showed one anodic peak and PMPY two anodic peaks. Their peak potentials were associated with conjugation length.