Experimental analysis of current and deformation of ion-exchange polymer metal composite actuators

In this paper we describe the experimental analysis of a novel ion-exchange polymer metal composite (IPMC) actuator under large external voltage. The experimental analysis is supplemented with a coupled thermodynamic model, which includes mass transport across the thickness of the polymer actuator, chemical reactions at boundaries, and deformation as a function of the solvent (water) distribution. In this paper, the case of large electrode potentials (over 1.2 V) has been analyzed experimentally and theoretically. At these voltage levels, electrochemical reactions take place at both electrodes. These are used in the framework of overpotential theory to develop boundary conditions for the water transport in the bulk of polymer. The model is then simplified to a three-component system comprised of a fixed negatively charged polymeric matrix, protons, and free water molecules within the polymer matrix. Among these species, water molecules are considered to be the dominant species responsible for the deformation of the IPMC actuators. Experiments conducted at different initial water contents are described and discussed in the context of the proposed deformation mechanism. Comparison of numerical simulations with experimental data shows good agreement.     

软x射线近贴显微技术

软x射线近贴显微技术不但可使活的生物样品成象,分辨率高于光学显微镜,而且人为的样品准备程序在该技术中都可避免。本文描述了用高功率激光打靶产生的等离子体作为软x射线源而进行的近贴显微研究,并得到了分辨率好于1μm的结果。     

Synthesis and Crystal Structure of a Ternary Complex: [Ni(phen)2(pmal)]·8H2O

A new ternary complex [Ni(phen)(pmal)]·8H2O (phen = 1,10-phenanthroline,pmal2- = phenethyl malonic acid) has been synthesized by the reaction of nickel acetate, phen and phenethyl malonic acid. Elemental analysis, IR spectra and X-ray single-crystal diffraction were carried out to determine the composition and crystal structure. Crystal data for this complex: triclinic system, space group P1, a = 10.387(5), b = 13.112(6), c = 14.229(6) (A), α = 76.176(7), β =83.778(8), y = 71.770(6)°, C35H42N4O12Ni, Mr= 769.44, Z = 2, F(000) = 808, V = 1786.1 (A)3, Dc =1.431 g/cm3, μ = 0.612 mm-1, the final R = 0.0653 and wR = 0.1033 for 9379 (Rint = 0.0244)independent reflections and 4730 observed reflections (I ＞ 2σ(I)). Structural analysis shows that the coordination geometry of Ni(Ⅱ) is a distorted octahedron. A novel two-dimensional structure is constructed from (H2O)4 and (H2O)12 water clusters, and the complex forms a 3-D network supramolecular structure by hydrogen bonds and π-π stacking of neighboring phens.     

Cationic poly(methacryl oxyethyl trimethylammonium) and its poly(ethylene glycol)‐grafted analogue as capillary coating materials in electrophoresis

Cationic polyelectrolytes were synthesized and used as semipermanent coating materials for capillaries in electrophoresis. The polyelectrolytes used were a homopolymer of poly(methacryl oxyethyl trimethylammonium chloride) (PMOTAC) and its poly(ethylene glycol) (PEG)‐grafted analogue. Two PMOTAC polyelectrolytes, with molar masses of 85,000 and 300,000 g/mol, and PEG‐grafted PMOTAC with a molar mass of 280,000 g/mol were synthesized and then characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Attachment of the polyelectrolytes to the wall of the fused silica capillary for electrophoresis caused the electroosmotic flow (EOF) to reverse. The polyelectrolyte coatings were tested over the pH range 2–11 at different buffer ionic strengths, and the most stable and strongest anodic EOFs were obtained at acidic pH values with low ionic strength buffers. Between runs the capillary is merely rinsed for 2 or 3 min with the background electrolyte solution. With the PMOTAC coatings at pH values ≤5, the RSDs of the EOFs were less than 2.9% after 60 injections. The effects of the molar mass of the polycation and of PEGylation of PMOTAC on the interactions between the polycations and basic proteins were studied at acidic pH values. The differences in the effective electrophoretic mobilities, resolution values, and plate numbers of the proteins with the different coatings were due to the EOF, as demonstrated through calculations of reduced mobilities, relative resolution values, and relative plate numbers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2655–2663, 2007     

Boundary-Value Problem of Drainage in a Fresh Groundwater Fringe above Saline Groundwater

A multiparameter boundary-value problem of fresh infiltration water seepage in a drained fringe above quiescent saline water is solved in the direct statement and studied in detail.     

Time saving fluid dynamic predictions in a wetting-drying process: A hypothesis for vertisols

This paper is aimed at investigating the effect of the initial water content in a vertisol sample on the whole wetting-drying process leading the system to a change in volume. In order to do this, an experimental setup was realized and employed with very thin soil layers wetted from below (“per ascensum”). The results show that the effect of the initial water content on the swelling-shrinkage process is to shift the corresponding curve e-ϑ towards bigger-smaller values of the humidity but does not seem to affect the dynamics of the process. The text was submitted by the authors in English.     

Synthesis and antibacterial activities of water‐soluble methacrylate polymers containing quaternary ammonium compounds

New water‐soluble methacrylate polymers with pendant quaternary ammonium (QA) groups were synthesized and used as antibacterial materials. The polymers with pendant QA groups were obtained by the reaction of the alkyl halide groups of a previously synthesized functional methacrylate homopolymer with various tertiary alkyl amines containing 12‐, 14‐, or 16‐carbon alkyl chains. The structures of the functional polymer and the polymers with QA groups were confirmed with Fourier transform infrared and ¹H and ¹³C NMR. The degree of conversion of alkyl halides to QA sites in each polymer was determined by ¹H NMR to be over 90% in all cases. The number‐average molecular weight and polydispersity of the functional polymer were determined by size exclusion chromatography to be 32,500 g/mol and 2.25, respectively. All polymers were thermally stable up to 180 °C according to thermogravimetric analysis. The antibacterial activities of the polymers with pendant QA groups against Staphylococcus aureus and Escherichia coli were determined with broth‐dilution and spread‐plate methods. All the polymers showed excellent antibacterial activities in the range of 32–256 μg/mL. The antibacterial activity against S. aureus increased with an increase in the alkyl chain length for the ammonium groups, whereas the antibacterial activity against E. coli decreased with increasing alkyl chain length. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5965–5973, 2006     

Chemically modified proton‐conducting membranes based on sulfonated polyimides: Improved water stability and fuel‐cell performance

A series of branched/crosslinked sulfonated polyimide (B/C‐SPI) membranes were prepared and evaluated as proton‐conducting ionomers based on the new concept of in situ crosslinking from sulfonated polyimide (SPI) oligomers and triamine monomers. Chemical branching and crosslinking in SPI oligomers with 1,3,5‐tris(4‐aminophenoxy)benzene as a crosslinker gave the polymer membranes very good water stability and mechanical properties under an accelerated aging treatment in water at 130 °C, despite their high ion‐exchange capacity (2.2–2.6 mequiv g^?1). The resulting polymer electrolytes displayed high proton conductivities of 0.2–0.3 S cm^?1 at 120 °C in water and reasonably high conductivities of 0.02–0.03 S cm^?1 at 50% relative humidity. In a single H₂/O₂ fuel‐cell system at 90 °C, they exhibited high fuel‐cell performances comparable to those of Nafion 112. The B/C‐SPI membranes also displayed good performances in a direct methanol fuel cell with methanol concentrations as high as 50 wt % that were superior to those of Nafion 112. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3751–3762, 2006     

Comprehensive study on the formation of polyelectrolyte complexes from (quaternized) poly[2‐(dimethylamino)ethyl methacrylate] and poly(2‐acrylamido‐2‐methylpropane sodium sulfonate)

Polyelectrolyte complexes (PECs) have been prepared from well‐defined (quaternized) poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) and high molecular weight poly(2‐acrylamido‐2‐methylpropane sodium sulfonate) (PAMPSNa) after a thorough study of their viscometric properties. The effect of pH and quaternization degree of PDMAEMA on PECs stoichiometry has been examined. PEC‐based materials have been characterized in terms of thermal stability, equilibrium swelling degree, and free/bound water composition. The stoichiometry and swellability of the physically crosslinked hydrogels obtained from fully quaternized PDMAEMA/PAMPSNa complexes do not depend on pH. In contrast, PECs made of non quaternized PDMAEMA and PAMPSNa are highly affected by pH, and could reversibly disintegrate at pH ≥ 9. Partially quaternized PDMAEMA/PAMPSNa PECs exhibit intermediate properties and form stable loose structures in the whole investigated pH range. Finally, stable dispersions of PECs nanoparticles have been successfully produced from dilute solutions of the complementary polyelectrolytes. The nanoparticle average diameter as determined by dynamic light scattering proved to depend on the molar fraction of DMAEMA‐based subunits and on the initial polyelectrolyte concentration. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5468–5479, 2006     

Measurement and prediction of solubilities and diffusion coefficients of carbon dioxide in starch–water mixtures at elevated pressures

The solubility and diffusion coefficient of carbon dioxide in intermediate‐moisture starch–water mixtures were determined both experimentally and theoretically at elevated pressures up to 16 MPa at 50 °C. A high‐pressure decay sorption system was assembled to measure the equilibrium CO₂ mass uptake by the starch–water system. The experimentally measured solubilities accounted for the estimated swollen volume by Sanchez–Lacombe equation of state (S‐L EOS) were found to increase almost linearly with pressure, yielding 4.0 g CO₂/g starch–water system at 16 MPa. Moreover, CO₂ solubilities above 5 MPa displayed a solubility increase, which was not contributed by the water fraction in the starch–water mixture. The solubilities, however, showed no dependence on the degree of gelatinization (DG) of starch. The diffusion coefficient of CO₂ was found to increase with concentration of dissolved CO₂, which is pressure‐dependent, and decrease with increasing DG in the range of 50–100%. A free‐volume‐based diffusion model proposed by Areerat was employed to predict the CO₂ diffusivity in terms of pressure, temperature, and the concentration of dissolved CO₂. S‐L EOS was once more used to determine the specific free volume of the mixture system. The predicted diffusion coefficients showed to correlate well with the measured values for all starch–water mixtures. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 607–621, 2006