Si—H Functional Polysilanes via a Homogeneous Reductive Coupling Reaction

A polysilane copolymer with reactive Si—H side groups was obtained through a homogeneous coupling reaction of dichlorodiphenylsilane with dichloromethylsilane. The reaction was carried out in a tetrahydrofuran (THF) solution of a sodium‐potassium alloy complex with 18‐crown‐6 with a well defined composition of alkali metal ion pairs (Mt⁺/crown ether, Mt^–) at –75°C. The product was characterized using ¹H NMR, ¹³C NMR, FT‐IR and UV/Visible spectroscopies and gel permeation chromatography. The results were compared with those obtained by the heterogeneous coupling reaction of the same monomers.     

Analysis of the end groups of poly(methyl methacrylate)

Methyl methacrylate polymerization by potassium hydride results in macromolecules with the methyl starting group. A side-reaction occurs during the process leading to potassium methoxide. It serves as the second initiator of the polymerization and gives macromolecules with the methoxy starting group. All macromolecules possess the methine group at the chain end after protonation. Potassium alkalide K⁻, K⁺(15-crown-5)₂ produces various active centres in the initial step of the polymerization. It results in macromolecules with the methyl, ethyl, methoxy and vinyl ether starting groups. However, the majority of macromolecules are formed on the species with two active centres. The termination reaction takes place during the polymerization, therefore, not all chains have the methine end group after protonation.     

Epoxypolyesters as film-forming materials

A series of solid epoxypolyesters were prepared by the condensation of glycols, 1,2,3,6-tetrahydrophthalic anhydride and dicyclopentadiene followed by the epoxidation of the double bonds in the unsaturated polyester. The polyesters were characterized and then subjected to photoinitiated cationic polymerization using triarylsulfonium salt as the photoinitiator. It was demonstrated that the coatings prepared from these epoxypolyesters exhibited good hardness, impact strength and degree of drying. The straightforward synthesis and high reactivity in cationic UV curing make these epoxypolyesters attractive as film forming materials.     

微载荷含油轴承摩擦性能研究Ⅱ.摩擦试验分析

采用自行研制的径向轴承微载荷摩擦试验机研究了微载荷下径向含油轴承的摩擦性能,采用小波方法对试验数据进行滤波降噪.结果表明,含油轴承在稳定微载荷状态下的瞬态摩擦系数不固定,且随着润滑剂、轴承转速、径向载荷与混合润滑状态等因素而变化.在微载荷状态下,当600 r/min、采用液晶添加剂(5CB)与46号机械油以体积比1%～2%配制的润滑剂润滑时,平均摩擦系数达到最小值;当转速从600 r/min增至3 000 r/min时,平均摩擦系数由小变大、再变小;瞬态摩擦系数随着载荷从0.5 N增至10.0 N呈现高-低-稳定的变化趋势.与混合润滑状态相比,充分润滑下的摩擦系数较大;当混合润滑时,在主轴转速为1 500～2 400 r/min下的摩擦系数出现不稳定.     

Application of EPR spectroscopy for elucidation of vanadium speciation in VO x /ZrO2 catalysts subject to redox treatment

Application of EPR spectroscopy corroborated by spectra simulation in speciation studies of the tetravalent vanadium in supported VO _x /ZrO₂ catalyst has been discussed. Implementation of genetic algorithms into automated analysis of the EPR spectra has greatly improved the simulation efficiency. The performance of the new procedure has been benchmarked against common simplex method using the multi-component model and real EPR spectra of tetravalent vanadium in VO _x /ZrO₂ catalysts. The analysis has revealed speciation of vanadium into surface isolated and clustered vanadyl entities and isolated bulk V _Zr ^x ions due to formation of Zr_1?x V _x O₂ solid solution in the near to surface region. The structural heterogeneity of vanadium can be controlled by the calcination temperature and the redox treatment.     

Sensitivity analysis of discontinuous parametric periodic systems

The paper concerns the complex eigensolutions sensitivity analysis of parametric periodic system. The derivatives of (so called) monodromy matrix (Floquet transient matrix) were the first calculated. Then the first derivatives of multiplicators, which are the complex eigenvalues of monodromy matrix, were obtained. The theory has been expanded to cover a class of discontinuous parametric periodic excitation. Furthermore, the method was generalized, so that the system parameters, on which the parametric excitation period depends, can now be a design parameter. In particular, it has become possible to use the parametric excitation period as a design parameter. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sensitivity analysis of multi-storey building due to blast loading

In this paper the vibration problems of multi-storey column-slab buildings are considered. Vibrations are caused by the explosion in the building and destruction of some construction elements. The influence of sudden loss of these elements as well as the explosion pressure are taken into account. In particular, the influence of destruction location on the building vibrations is examined. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Novel supramolecular catalysis in the controlled synthesis of polymers and block copolymers

Novel carbanionic polymerization of vinyl monomers as styrene, methyl methacrylate, as well as ring opening polymerization of oxiranes and lactones mediated by supramolecular complexes of alkali metals is demonstrated.