Permeation of nitrogen and water vapor through sulfonated polyetherethersulfone membrane

The novel polyetherethersulfone (PES-C) prepared from phenol-phthalein in our institute is an amorphous, rigid, tough material with good mechanical properties over a wide temperature range. To improve its water vapor permeability for the application of gas drying, the PES-C was sulfonated with concentrated sulfuric acid and transferred in sodium, cupric, and ferric salt forms. The sulfonation degree can be regulated by controlling the temperature and reaction time. Characterization of sulfonated PES-C in sodium form was made by IR. Some properties of the sulfonated PES-C, such as solubility, glass transition temperature, thermal stability, mechanical properties, and transport properties to nitrogen and water vapor have also been discussed. (C) 1997 John Wiley & Sons, Inc.

Isolation, spectra, structure, and ring-opening polymerization of strained macrocyclic aryl(ether ketone) dimer

Macrocyclic arylene ether ketone dimer was isolated from a mixture of cyclic oligomers obtained by the nucleophilic substitution reaction of bisphenol A and 4,4'-difluorobenzophenone and easily polymerized to high molecular weight linear poly(ether ketone). The cyclic compound was characterized by FTIR, H-1- and C-13-NMR, and single-crystal x-ray diffraction. Analysis of the spectral and crystal structure reveals extreme distortions of he phenyl rings attached to the isopropylidene center and of the turning points of the molecular polygons. The release of the ring strain on ring-opening combined with entropical difference between the linear polymer chain and the more rigid macrocycle at temperatures of polymerization may be the proposed motivating factors in the polymerization of this precursor to high molecular weight poly(ether ketone). (C) 1997 John Wiley & Sons, Inc.

Sulfonation of polyetheretherketone and its effects on permeation behavior to nitrogen and water vapor

The novel polyetheretherketone (PEK-C) prepared from phenolphthalein in our institute is an amorphous, rigid, tough material with good mechanical properties over a wide temperature range. To improve its water vapor permeability for the application of gas drying, PEK-C was sulfonated with concentrated sulfuric acid and transferred in sodium, cupric, and ferric salt forms. Sulfonation degree can be regulated by controlling the temperature and reaction time. Characterization of sulfonated PEK-C in sodium form was made by infrared spectroscopy. Some properties of the sulfonated PEK-C, such as solubility, glass transition temperature, thermal stability, mechanical properties, and transport properties to nitrogen and water vapor, are also discussed. (C) 1996 John Wiley & Sons, Inc.

Influence of crystal structure on the luminescence properties of bismuth(III), europium(III) and dysprosium(III) in Y2SiO5

The luminescence properties of Bi3+, EU(3+), Dy3+ and energy transfer from Bi3+ to Dy3+ and EU(3+) have been studied in two modifications of Y2SiO5 (low-temperature X(1) type and high-temperature X(2) type) and discussed in relation to their crystal structures. The Bi3+ ion luminesces in the blue region of the spectrum in X(1)-Y2SiO5 but in the UV region in X(2)-Y2SiO5. Two obviously different luminescent centres have been observed for Bi3+ and Eu3+ ill X(1)-Y2SiO5, but only one has been seen in X(2)-Y2SiO5. The Stokes shift (9200 cm(-1)) for Bi3+ in X(1)-Y2SiO5 is much larger than that (5000 cm(-1)) in X(2)-Y2SiO5. This suggests that the host lattice is more rigid in X(2)-Y2SiO5 than in X(1)-Y2SiO5. As a result, the Bi3+, EU(3+) and Dy3+ ions show higher emission intensity in the former than in the latter type. X(1)-Y2SiO5 is more suitable for Bi3+ --> EU(3+) energy transfer and X(2)-Y2SiO5 is more suitable for Bi3+ --> Dy3+ energy transfer.

NMR-STUDY OF MISCIBILITY AND MORPHOLOGY OF POLYIMIDE POLYIMIDE BLENDS

The miscibility and morphology of polyimide/polyimide blends, PEI-E/PTI-E(a)) and PBPI-E/IPTI-E(a)), have been studied by means of C-13 CPMAS NMR technique. The results indicate that PEI-E/PTI-E blends are miscible on a molecular level, but molecular aggregation exists in pure PBPI-E specimen as well as PBPI-E/PTI-E blends with high content of PBPI-E, which vanishes in the blends with high content of PTI-E. When the content of PBPI-E is higher than that of PTI-E, the addition of PTI-E to PBPI-E has almost no effect on the size of the PBPI-E rigid domains, but has a large effect on the populations of the PBPI-E rigid domains. It is the intermolecular charge-transfer interaction that plays a critical role in the miscibility of PEI-E/PTI-E and PBPI-E/PTI-E blends.

SOLID-STATE VOLTAMMETRY OF ELECTROACTIVE SOLUTES IN POLYMER SOLVENTS (PEO) AT ULTRAMICROELECTRODES

This paper describes the electrochemical oxidation and reduction of electroactive solutes which are dissolved in and diffusing through the polymer electrolyte solvent, poly(ethylene oxide) (PEO). The characteristics of electrochemical reactions in polymeric solutions are discussed, including how rigid solvent environments affect mass transport rates, and the transport phenomenon of electroactive species in PEO with bathing gases is explained by using the voltammetric theory of ultramicroelectrodes. The possibility that the microelectrode coated with PEO film can be used as a gas sensor has been discussed.

SYNTHESIS AND PROPELLER PROPELLER TRANSITION OF OPTICALLY-ACTIVE POLY(DIPHENYL-O-METHOXYPHENYLMETHYL METHACRYLATE)

Diphenyl-o-methoxyphenylmethyl methacrylate was polymerized with several organolithium complexes of chiral ligand such as (-)-sparteine (Sp) and (S,S)-(+)-2,3-dimethoxy-1,4-bis(dimethylamino)butane (DDB). (+)-DDB was effective in preparing a polymer of high optical rotation, whereas (-)-Sp only gave oligomers with low optical rotation for the repulsive hindrance between the bulky ester group and the rigid ligand. The optical rotation of the polymer decreased rapidly to a constant value due to the propeller-propeller transition, which has been demonstrated by H-1 n.m.r. and circular dichroic spectra.

MICROSTRUCTURE ANALYSIS OF 3 SEGMENTED COPOLYMERS CONTAINING POLYDIMETHYLSILOXANE BY SOLID-STATE HIGH-RESOLUTION NMR

The microstructure of two bicomponent and one tricomponent segmented copolymers, based on polydimethylsiloxane, poly(p-hydroxystyrene) or/and polysulfone, were investigated using an extended Goldman-Shen pulse sequence, proton spin-spin relaxation measurements, and C-13 and Si-29 NMR spectra. The results indicate that there exist four phases with different sizes, components and morphological structure in the segmented copolymers studied in this work, i. e., a rigid-chain phase of very slow motion, a rigid-chain-rich phase of slow motion, a flexible-chain-rich phase of fast motion and a flexible-chain phase of faster motion. The sizes of different domains, calculated from the spin diffusion rates, are about 50-100 angstrom for the flexible-chain-rich phase of fast motion and 200-300 angstrom for the flexible-chain phase of faster motion. The relative quantities of polydimethylsiloxane in the flexible-chain phase of fast motion are slightly different in different kinds of segmented copolymers.

BETA-RELAXATION IN POLYIMIDES

A series of polyimides with different structures have been synthesized and studied by dynamic mechanical analysis. The results obtained indicate that the beta relaxation in polyimides is related to the rotation of rigid segment(s) of p-phenylene and imide groups around 'hinges' such as -O-, -CH2- and so on in diamines. It is noticed that two kinds of polyimides both with [GRAPHICS] imide groups have verv weak beta relaxation below the glass transition temperature. This phenomenon is due to the fact that the configuration of chains with the above imide groups hinders the rotation of the rigid segments in the chains.

HREM IMAGING OF POLY(ARYL-ETHER-KETONE) CRYSTAL

High resolution transmission electron microscope (HREM) was used to observe the rigid chain polymer poly(aryl-ether-ketone) (PEK), so as to study the morphology of the crystals and molecular arrangement within a crystal.Many kinds of material crystal structures have been studied with HREM in recent years. So far as polymeric materials are concerned, the application of HREM

Higher-order Boussinesq-type equations for interfacial waves in a two-fluid system

Interfacial waves propagating along the interface between a three-dimensional two-fluid system with a rigid upper boundary and an uneven bottom are considered. There is a light fluid layer overlying a heavier one in the system, and a small density difference exists between the two layers. A set of higher-order Boussinesq-type equations in terms of the depth-averaged velocities accounting for stronger nonlinearity are derived. When the small parameter measuring frequency dispersion keeping up to lower-order and full nonlinearity are considered, the equations include the Choi and Camassa's results (1999). The enhanced equations in terms of the depth-averaged velocities are obtained by applying the enhancement technique introduced by Madsen et al. (1991) and Schaffer and Madsen (1995a). It is noted that the equations derived from the present study include, as special cases, those obtained by Madsen and Schaffer (1998). By comparison with the dispersion relation of the linear Stokes waves, we found that the dispersion relation is more improved than Choi and Camassa's (1999) results, and the applicable scope of water depth is deeper.

A kind of extended Korteweg-de Vries equation and solitary wave solutions for interfacial waves in a two-fluid system

This paper considers interfacial waves propagating along the interface between a two-dimensional two-fluid with a flat bottom and a rigid upper boundary. There is a light fluid layer overlying a heavier one in the system, and a small density difference exists between the two layers. It just focuses on the weakly non-linear small amplitude waves by introducing two small independent parameters: the nonlinearity ratio epsilon, represented by the ratio of amplitude to depth, and the dispersion ratio mu, represented by the square of the ratio of depth to wave length, which quantify the relative importance of nonlinearity and dispersion. It derives an extended KdV equation of the interfacial waves using the method adopted by Dullin et al in the study of the surface waves when considering the order up to O(mu(2)). As expected, the equation derived from the present work includes, as special cases, those obtained by Dullin et al for surface waves when the surface tension is neglected. The equation derived using an alternative method here is the same as the equation presented by Choi and Camassa. Also it solves the equation by borrowing the method presented by Marchant used for surface waves, and obtains its asymptotic solitary wave solutions when the weakly nonlinear and weakly dispersive terms are balanced in the extended KdV equation.

全地形轮式移动机器人运动学建模与分析

提出全地形轮式移动机器人的正逆运动学问题。将机器人看成一个混合串-并联多刚体系统,从每个轮-地接触点到机器人车体分别构成一个串联子系统,抛弃车轮纯滚动假设,在轮-地接触点处建立瞬时坐标系,考虑车轮的平面滑移,从而对每个串联子系统形成一个封闭的速度链。对于每个速度闭链,可直接在驱动轮轮心处写出从机器人各驱动轮到机器人本体之间的运动方程,将每个速度闭链的运动方程合并即可得到机器人的整体运动学模型。以一个具有被动柔顺机构的六轮全地形移动机器人为对象进行推导,该方法既考虑了地形不平的影响,又考虑了车轮的前向、侧向及转向滑移,已知机构参数后就可以直接写出机器人的速度方程,且便于运动学求解。该方法对于轮式移动机器人的运动学建模具有一般性,且具有物理意义明确、推导过程简洁等特点。

全地形移动机器人轮-地几何接触角估计

研究全地形移动机器人在不平坦地形中轮-地几何接触角的实时估计问题.本文以带有被动柔顺机构的六轮全地形移动机器人为对象,抛弃轮-地接触点位于车轮支撑臂延长线上这一假设,通过定义轮-地几何接触角δ来反映轮-地接触点在轮缘上位置的变化和地形不平坦给机器人运动带来的影响,将机器人看成是一个串-并联多刚体系统,基于速度闭链理论建立考虑地形不平坦和车轮滑移的机器人运动学模型,并针对轮-地几何接触角δ难以直接测量的问题,提出一种基于模型的卡尔曼滤波实时估计方法.利用卡尔曼滤波对机器人内部传感器的测量值进行噪声处理,基于机器人整体运动学模型对各个轮-地几何接触角进行实时估计,物理实验数据的处理结果验证了本文方法的有效性,从而为机器人运动学的精确计算和高质量的导航控制奠定了基础.

一种3自由度并联柔索驱动柔性操作臂的建模与控制

以一种3自由度并联柔索驱动机器人为研究对象,研究这种并联柔性系统的控制规律。考虑到运动描述的唯一性及易测性,取约束关节的位置作为广义关节变量,用以描述操作臂的运动状态。在此基础上分析了操作臂的运动学和静力学关系,建立了并联柔性系统的动力学模型。然后,以轨迹控制为目标,分别基于刚性模型和柔性模型设计控制器,并对系统的性能进行分析和仿真。结果表明:基于刚性模型控制器的性能较差,而基于柔性模型的奇异摄动方法则可以获得较好的控制效果。