SHAPE MEMORY EFFECT OF PU IONOMERS WITH IONIC GROUPS ON HARD-SEGMENTS

SMPU （shape memory polyurethane） non-ionomers and ionomers, synthesized with poly（c-caprolactone） （PCL）, 4, 4＇-diphenylmethane diisocyanate （MDI）, 1,4-butanediol （BDO）, dimethylolpropionic acid （DMPA） were measured with cyclic tensile test and strain recovery test. The relations between the structure and shape memory effect of these two series were studied with respect to the ionic group content and the effect of neutralization. The resulting data indicate that, with the introduction of asymmetrical extender, the stress at 100% elongation is decreased for PU non-ionomer and ionomer series, especially lowered sharply for non-ionomer series; the fixation ratio of ionomer series is not affected obviously by the ionic group content; the total recovery ratio of ionomer series is decreased greatly. After sufficient relaxation time for samples stretched beforehand, the switching temperature is raised slightly, whereas the recovery ratio measured with strain recovery test method is lowered with increased DMPA content. The characterization with FT-IR, DSC, DMA elucidated that, the ordered hard domain of the two series is disrupted with the introduction of DMPA which causes more hard segments to dissolve in soft phase; ionic groups on hard segment enhance the cohesion between hard segments especially at high ionic group content and significantly facilitate the phase separation compared with the corresponding non-ionomer at moderate ionic group content.     

Thermoanalytische Untersuchungen an Schichtmaterialien: Der Einfluβ der Kationen auf das thermische Verhalten

Aluminium-free layered silicates of the metal silicate hydrate type (M-SH) comprise an interesting supplement to the well-known zeolite-like porous materials. Their specific properties allow these materials to be used as catalysts, adsorbents and ion-exchangers. Comparative X-ray diffraction and thermoanalytical investigations (TG and DSC) have shown that the thermoanalytical methods are useful to follow the process of structure formation of ilerite. The interlayer cations influence the properties of the different ilerites. In particular, the hydration behaviour of ilerite is affected. Thus, H⁺- and DTMA⁺-ilerite are stable up to temperatures of about 800°C, while the as-synthesized Na-form loses water irreversibly at about 150°C, is dehydroxylated, and is then desomposed structurally at about 400°C. The course of the dehydration exhibits significant differences for the various cation forms.This revised version was published online in November 2005 with corrections to the Cover Date.     

Microgravimetric Investigations of High-Temperature Superconductors

It has been confirmed that, in oxide superconductors, the superconducting transition temperature T_c depends strongly on the oxygen content and oxygen ordering. The microgravimetric method is very useful in the analysis of oxide superconductors, because it allows investigations in vacuum and controlled environments in classical applications: thermogravimetric analysis, kinetics and thermodynamics of reaction, determination of oxygen contents in redox reactions, investigations of the correlation of the deviation from stoichiometry and carrier concentration and also the combined measurement of mass and additional parameters, e.g. evolved gas analysis, etc. Selected papers are reviewed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of organic ligands on the stabilization of palladium nanoparticles

The synthesis of palladium nanoparticles is performed by hydrogenation of a precursor, Pd₂(dba)₃ (1) or [Pd(C₃H₅)Cl]₂ (2) in the presence of either a weakly coordinating ligand (hexadecylamine, HDA) or good ligands (polyphosphines). It is shown in the case of 1 that good ligands lead to stable spherical nanoparticles of small size (near 2 nm) whereas the protective effect of HDA depends on the amount of ligand added as a result of equilibria present at the surface of the particles as monitored by solution NMR spectroscopy. The decomposition of 2 being very fast, the particle growth cannot be controlled except in the case of the use of a large excess of HDA which leads to spongelike particles resulting from the agglomeration of initially obtained nanocrystallites.     

高校体育俱乐部现状的实证调查与分析

通过对公共体育教学改革走在国内前面的南京师范大学、上海中医大学和深圳大学进行调查,并对3所高校体育俱乐部现状的优缺点进行分析,同时对杭州师范学院教学改革提出了一些建议,目的是为该院的体育课程教学改革提供参考.     

Indole-Based Tubulin Inhibitors: Binding Modes and SARs Investigations

Tubulin inhibitors can interfere with normal cell mitosis and inhibit cell proliferation through interfering with the normal structure and function of microtubules, forming spindle filaments. Indole, as a privileged pharmacological skeleton, has been widely used in anti-cancer inhibitors. A variety of alkaloids containing an indole core obtained from natural sources have been proven to inhibit tubulin polymerization, and an ever-increasing number of synthetic indole-based tubulin inhibitors have been reported. Among these, several kinds of indole-based derivatives, such as TMP analogues, aroylindoles, arylthioindoles, fused indole, carbazoles, azacarbolines, alkaloid nortopsentin analogues and bis-indole derivatives, have shown good inhibition activities towards tubulin polymerization. The binding modes and SARs investigations of synthetic indole derivatives, along with a brief mechanism on their anti-tubulin activity, are presented in this review.     

Temperature induced rotation in a [4.4]cyclophane

The synthesis, the X-ray, NMR and molecular modeling structure determination of a new orthopara[4.4]cyclophane are reported. The similarity of the π(CO)-π(Ar) driven conformational equilibrium of this compound to the work of an amusement ride machinery is also revealed.     

Structural characterization of AlN films synthesized by pulsed laser deposition

We obtained AlN thin films by pulsed laser deposition (PLD) from a polycrystalline AlN target using a pulsed KrF* excimer laser source (248 nm, 25 ns, intensity of ∼4 × 10⁸ W/cm², repetition rate 3 Hz, 10 J/cm² laser fluence). The target-Si substrate distance was 5 cm. Films were grown either in vacuum (10⁻⁴ Pa residual pressure) or in nitrogen at a dynamic pressure of 0.1 and 10 Pa, using a total of 20,000 subsequent pulses. The films structure was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and spectral ellipsometry (SE). Our TEM and XRD studies showed a strong dependence of the film structure on the nitrogen content in the ambient gas. The films deposited in vacuum exhibited a high quality polycrystalline structure with a hexagonal phase. The crystallite growth proceeds along the c-axis, perpendicular to the substrate surface, resulting in a columnar and strongly textured structure. The films grown at low nitrogen pressure (0.1 Pa) were amorphous as seen by TEM and XRD, but SE data analysis revealed ∼1.7 vol.% crystallites embedded in the amorphous AlN matrix. Increasing the nitrogen pressure to 10 Pa promotes the formation of cubic (≤10 nm) crystallites as seen by TEM but their density was still low to be detected by XRD. SE data analysis confirmed the results obtained from the TEM and XRD observations.     

一种中高温热泵混合工质的实验研究

提出了一种适用于90-110℃冷凝温度范围的HFC类中高温热泵非共沸混合工质,其理论循环性能优于CFC114,实测COP为纯工质HFC245fa的97.2%-130.6%、制热量高于HFC245fa。     

On the Donor Ability of the Phosphaneiminato Substituent and Cube Formation with Transition Metal Fragments

The particular role of the phosphaneiminato ligand as a donor is investigated for a) nitrenes (phosphinidenes) and carbenes and b) cubane formation with transition metals. Accordingly, and as shown for the case a) the ligand is a stronger π‐donor than an amino group and can be considered as a special case of imine‐type substituents. The latter are very effective in π‐donation. In the case b), i.e. the cubane formation with transition metals, one has to consider transition metals with a partially or completely filled d‐shell (with electrons). Hence depending on the transition metal, cubanes are build with weak ferromagnetic coupled or closed shell systems. For the cubanes with closed shell character the matter of insertion of halide anions is discussed. In the last chapter of the review the bond stretching in the dithionitrosyl complexes with rhenium is characterized.