Preparation of polymer/silica nanoscale hybrids through sol-gel method involving emulsion polymers. II. Poly(ethyl acrylate)/SiO2

Poly(ethyl acrylate) (PEA)/SiO2 hybrids with different compositions were prepared under different casting temperatures and pH values. Their morphology as investigated by transmission electron microscopy (TEM) shows that samples with different compositions have different morphologies. When the SiO2 content is lower, PEA is the continuous phase and SiO2 is the dispersed phase. At higher SiO2 content, the change in phase morphology takes place, nd PEA gradually dispersing in the form of latex particles in SiO2 matrix. Change in phase morphology depends mainly on the time the sol-gel transition occurs. At suitable casting temperature and pH value, PEA/SiO2 in 95/5 and 50/50 hybrids with even dispersion was obtained.

Study of the ionic conductivity of polymer electrolyte using imaginary impedance spectroscopy

Polymeric electrolytes of (PEO1)(10) LiClO4-Al2O3 (PEO: poly (ethyleneoxide)) and (PEO2)(16)LiClO4-EC (EC: ethylene carbonate) were prepared. We proposed an equivalent circuit and gave the meaning of the concerned circuit elements. When the impedance spectrum deformed severely, the ionic conductivity of polymer electrolyte was determined by using the maximum of imaginary impedance, which is a convenient method.

Advances in ionic conductive polymer electrolytes

The history of solid state electrolyte, the categories, ion transport mechanism, characterization, and the methods to raise the ionic conductivities of polymer electrolytes are reviewed. The further required attentions in the development of polymer electrolytes are discussed in the final part of the review.

Effect of properties of active carbon supports on performance of Pt/C catalysts in polymer electrolyte membrane fuel cell

The Pt/C catalysts were prepared with pine active carbon and Vulcan XC-72 active carbon as the supports. The performances of the Pt/C catalysts in polymer electrolyte membrane fuel cell were compared. The result indicates that the performance of Pt/Vulcan XC-72 is better than that of Pt/pine. The physical and chemical properties of the two active carbons were measured using several analysis techniques. It was found that the pore size, specific conductivity and the surface function group significantly influence the performance of the electrocatalyst.

Polymer immobilized silane bridged metallocene catalysts for ethylene polymerization

Ansa-zirconocene complex with an allyl substituted silane bridge [(CH2=CHCH2)CH3Si(C5H4)(2)]ZrCl2 (1a) has been synthesized and characterized. The molecular structure of la has been determined by X-ray crystallographic analysis. The polymer immobilized metallocene catalyst 1b is prepared by the co-polymerization of la with styrene in the presence of radical initiator. The result of ethylene polymerization showed that the polymer immobilized metallocene catalyst kept high activity for ethylene polymerization and was a potential supported catalyst for olefin polymerization.

Liquid-phase hydrogenation of furfural to tetrahydrofurfuryl alcohol catalyzed by polymer resin supported palladium catalysts

Three kinds of polymer resin supported Pd catalysts were prepared by mixing PdCl2, with alkaline styrene anion exchange resins[D392 -NH2, D382, -NHCH3, D301R, -NH(CH3)(2)], strongly alkaline styrene anion exchanged resin [201 X 7DVB, -NH+ (CH3)(3)] and alkaline epoxy exchange resin (701, -NH2), and hydrogenating in liquid phase at 1.013 X 10(5) Pa. The hydrogenation of furfural was studied under the reaction conditions such as solvent, temperature. Pd content in the supported catalyst and the amount of the catalyst. The yield of hydrogenation reaction of furfural markedly increased to 100% and the selectivity to tetrahydrofurfuryl alcohol increased to over 98% by polymer (alkaline styrene anion exchange resins D392, -NH2, D382, -NHCH3) supported palladium catalysts comparing with the yield over 70% and selectivity over 97% by palladium catalyst, in 50% alcohol-50% water or pure water solution at 1.013 X 10(5) Pa. The relationship between hydrogenation and the structures of functional group in the supporting resin was examined by XPS method.

Incorporation of surface-derivatized gold nanoparticles into electrochemically generated polymer films

Stable colloidal solutions of gold nanoparticles surface-derivatized with a thiol monolayer have been prepared using two-phase (water-nitrobenzene) reduction of AuCl4- by sodium borohydride in the presence of 2-mercapto-3-n-octylthiophene (MOT). This kind of surface-functionalized gold nanoparticles can be easily incorporated into the poly(3-octylthiophene) (POT) films on electrode in the process of electrochemical polymerization leading to POT-gold nanoparticle (POT-Au) composite films. Scanning probe microscopy (SPM) and X-ray photoelectric spectroscopy (XPS) have been employed to characterize the surface-derivatized particles and the resulting films. The method of incorporation of nanoparticles into polymer by surface-derivatization and in situ polymerization can also be employed to prepare many other polymer-nanoparticle compostie materials.

Tensile modulus of polymer nanocomposites

Based on Takayanagi's two-phase model, a three-phase model including the matrix, interfacial region, and fillers is proposed to calculate the tensile modulus of polymer nanocomposites (E-c). In this model, fillers (sphere-, cylinder- or plate-shape) are randomly distributed in a matrix. If the particulate size is in the range of nanometers, the interfacial region will play an important role in the modulus of the composites. Important system parameters include the dispersed particle size (t), shape, thickness of the interfacial region (tau), particulate-to-matrix modulus ratio (E-d/E-m), and a parameter (k) describing a linear gradient change in modulus between the matrix and the surface of particle on the modulus of nanocomposites (E-c). The effects of these parameters are discussed using theoretical calculation and nylon 6/montmorillonite nanocomposite experiments. The former three factors exhibit dominant influence on E-c At a fixed volume fraction of the dispersed phase, smaller particles provide an increasing modulus for the resulting composite, as compared to the larger one because the interfacial region greatly affects E-c. Moreover, since the size of fillers is in the scale of micrometers, the influence of interfacial region is neglected and the deduced equation is reduced to Takayanagi's model. The curves predicted by the three-phase model are in good agreement with experimental results. The percolation concept and theory are also applied to analyze and interpret the experimental results.

Reactive reinforcement of the interface of poly(ether sulfone)/poly(phenylene sulfide) polymer blend by PMR-POI

The effect of polymerization of monomer reactant-polyimide (POI) as the interfacial agent on the interface characteristics, morphology features, and crystallization of poly(ether sulfone)/poly(phenylene sulfide) (PES/PPS) blends were investigated using a scanning electron microscope, FTIR, WAXD, and XPS surface analysis. It was found that the interfacial adhesion was enhanced, the particle size of the dispersed phase was reduced, and the miscibility between PES and PPS was improved by the addition of POI. It was also found that POI was an effective nucleation agent of the crystallization for PPS.

Novel bipolar conjugated polymer containing both triphenylamine and oxadizole units

A novel bipolar conjugated polymer containing triphenylamine and 1, 3, 4-oxadiazole units was synthesized by Suzuki reaction. Its structure and properties were characterized by NMR, IR, UV-Vis, PL spectroscopy and electrochemical measurement. The photo luminescent spectroscopy and cyclic voltammograms measurement demonstrated that the resulting polymer shows blue emission (477 nm) and possesses both electron and hole-transporting property.

Statistical thermodynamics of polydisperse polymer systems in the framework of lattice fluid model: Effect of molecular weight and its distribution on the spinodal in polymer solution

With the aid of thermodynamics of Gibbs, the expression of the spinodal was derived for the polydisperse polymer-solvent system in the framework of Sanchez-Lacombe Lattice Fluid Theory (SLLFT). For convenience, we considered that a model polydisperse polymer contains three sub-components. According to our calculation, the spinodal depends on both weight-average ((M) over bar (w)) and number-average ((M) over bar (n)) molecular weights of the polydisperse polymer, but the z-average molecular weight ((M) over bar (z)) dependence on the spinodal is invisible. The dependence of free volume on composition, temperature, molecular weight, and its distribution results in the effect of (M) over bar (n) on the spinodal. Moreover, it has been found that the effect of changing (M) over bar (w) on the spinodal is much bigger than that of changing (M) over bar (n) and the extrema of the spinodal increases with the rise of the weight-average molecular weight of the polymer in the solutions with upper critical solution temperature (UCST). However, the effect of polydispersity on the spinodal can be neglected for the polymer with a considerably high weight-average molecular weight. A more simple expression of the spinodal for the polydisperse polymer solution in the framework of SLLFT was also derived under the assumption of upsilon(*)=upsilon(1)(*)=upsilon(2)(*) and (1/r(1)(0))-(1/r(2i)(0))-->(1/r(1)(0)).

Preparation of polymer/silica nanoscale hybrids through sol-gel method involving emulsion polymers (PMMA/SiO2)

The different poly (methyl methacrylate) (PMMA) /SiO2 hybrids were prepared through sol-gel method involving PMMA emulsion (emulsion method) and PMMA/THF solution (solution method). The samples were characterized by differential scanning calorimetry(DSC), thermogravimetry analysis(TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that PMMA/SiO2 composites in nanoscale were prepared by emulsion method, and its size of phase heterogeneity was less than that of solution method. Meanwhile, the polymer emulsion as the reactive medium was more suitable for the formation of SiO2 network.

Plasticizer effect on the ionic conductivity of PEO-based polymer electrolyte

The effects of plasticizer ethylene carbonate (EC) on the AC impedance spectra and the ionic conductivity are reported. With increasing of EC concentration the semicircle in high frequency disappears, and the slope of the straight line in low frequency decreases. The data obtained from impedance experiments can be explained using an equivalent circuit proposed. On the other hand, the room temperature conductivity increases with EC concentration because of the increase of the segmental flexibility of PEO. For lower EC concentration samples, the temperature dependence of conductivity in low temperature range follows Arrhenius type, but when EC concentration is larger than 20%, the temperature dependence of conductivity obeys the Vogel-Tamman-Fulcher (VTF) equation in all temperature ranges.