Nonlinear Current-Voltage Curves for Thin-Film Gas-Sensitive Structures

Current-voltage curves for sensor structures based on thin tin oxide films are examined in various gases. Conditions favoring symmetrical nonlinear curves in the voltage range −30 to 30 V are found.__________Translated from Elektrokhimiya, Vol. 41, No. 6, 2005, pp. 735–737.Original Russian Text Copyright © 2005 by Simakov.Published on the basis of a report delivered at the VII Meeting on Fundamental Problems in Solid-State Ionics (Chernogolovka-2004).     

A DSC-Study of Donor/Acceptor Side-Chain Polymers with Flourinated Taper-Shaped Tails

It is shown that insertion in methacrylic polymers of bulky electron donor/acceptor side-groups with taper-shaped flourinated tails promotes a self-organization of the respective side-chain polymers due to the space demands of the bulky D/A side-groups, leading to a columnar hexagonal mesophase. The presence of an Lc-phase is evidenced by DSC and identified by X-ray analysis. The orientation in the respective copolymers and polymer blends is additionally improved by the CT-interaction between the D/A side-groups. An increased packing effect due to this CT-orientation effect is evidenced in DSC by an increase of the respective transition temperatures. CT-interaction is responsible as well for a preferential polymerization of monomeric D/A-complexes leading to copolymers of alternating structures and for a zip-like arrangement along the main chain of the A/D-complexes between the interacting side-groups in polymer blends. Formation of mesophases is even observed in CT-interacting blends between the Lc-D/A side-chain polymethacrylates and the respective amorphous D/A side-chain polysiloxanes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Transport properties of alkanes through ceramic thin zeolite MFI membranes

Polycrystalline randomly oriented defect free zeolite layers on porous α-Al₂O₃ supports are prepared with a thickness of less than 5 μm by in situ crystallisation of silicalite-1. The flux of alkanes is a function of the sorption and intracrystalline diffusion. In mixtures of strongly and weakly adsorbing gases and a high loadings of the strongly adsorbing molecule in the zeolite poze, the flux of the weakly adsorbing molecule is suppressed by the sorption and the mobility of the strongly adsorbing molecule resulting in pore-blocking effects. The separation of these mixtures is mainly based on the sorption and completely different from the permselectivity. At low loadings of the strongly adsorbing molecules the separation is based on the sorption and the diffusion and is the same as the permselectivity. Separation factors for the isomers of butane (n-butane/isobutane) and hexane (hexane/2,2-dimethylbutane) are respectively high (10) and very high (> 2000) at 200°C. These high separation factors are a strong evidence that the membrane shows selectivity by size-exclusion and that transport in pores larger than the zeolite MFI pores (possible defects, etc) can be neglected.     

Immobilization of α-amylase in vinyl-polymer-based interpenetrating polymer networks

Semi-interpenetrating polymer networks (IPNs) of poly(ethylene glycol), poly(vinyl alcohol) and polyacrylamide were prepared as a support for enzyme immobilization and kinetic studies were performed for the immobilization of -amylase. The effect of IPN composition on the extent of immobilization was investigated and the percentage of relative activity of the immobilized enzyme was evaluated as a function of the chemical architecture of the IPNs, pH and temperature, taking starch as a substrate. The kinetic constants and the maximum reaction velocity were also evaluated. The IPNs were characterized by IR spectral analysis.     

β—芳氧基丙酸衍生物的合成及生物活性

合成了β－芳氧基丙酸芳酯及β－芳氧基丙酰芳胺等１７种化合物，经ＩＲ，ＵＶ，ＨＮＭＲ和元素分析确定了它们的结构，并对它们的生物活性进行了初步考察。     

ξ-potential and surface dye-ability of poly(vinyl alcohol) fiber with different degree of formalization in a cationic dye solution

Summary The surface dyeability of the poly(vinyl alcohol) fiber with different degree of formalization was studied by measuring -potential of the fiber in alkaline aqueous solutions (pH 10) of a cationic dye Methylene Blue. With the increase in the dye concentration, the sign of the -potential of the fiber changed from negative to positive and thereafter the positive value approximated to saturated value, and the amount of dye adsorbed (expressed in mol/cm²-fiber) increased also. These results may possibly be attributed to the formation of the electrostatic bond between the fiber and the dye. The linear relations were found between and logC _d and its slope did not change with rise of temperature. The free energy of dyeing G (negative) calculated from the slope of the -logC _id curve, etc. increased with increasing the degree of formalization of the fiber. This fact corresponds to the increase in the surface dye adsorption with increasing the degree of formalization. With increasing the degree of formalization, the heat of dyeing H (negative) increased and the entropy of dyeing S (positive) decreased. The positive value of S for each fiber, suggests the formation of hydrophobic bond as a driving force to the dyeing of Methylene blue on the fiber surface in addition to the electrostatic bond.This paper is Part XXVII in a series on Studies on -potentials and Surface Dyeability of Natural and Synthetic Fibers in Dye Solution. Part XXVI: T. Suzawa andK. Kawakami, Nippon Kagaku Kaishi1975, No. 7,1134.