The Effect of the Chain Length on MMA Free Radicl Polymerization

It has been known that the propagation rate coefficient (kp) will change with monomer conversion, Friss, Hamielec et al.1-5 have proposed many formulas about kp to fit this change. In order to obtain the relation between Arrhenius parameters and monomer conversion, a group of kp values at the same monomer conversion must be measured. We adopted a new method through analysis of kp values measured by usual experimental techniques for this purpose. Firstly, we chose a value of monomer convers…     

Chiral Separation of N-Benzoyl Phenylalanine Methyl Ester by Nonaqueous Capillary Electrophoresis

Theseparationofopticalisomersisarapidlygrowingareaincapillaryelectrophoresis(CE),andmostchiralseparationbyCEhavebeenperformedinaqueousbackgroundelectrolyte.Organicsolventssuchasmethanolandacetonitrilehavebeenappliedasbuffermodifiersatconcentrationtypicallynothigherthan40%inordertoincreasehydrophobicanalytesolubilityandtoimproveselectivity,resolution,ortoaltertheelectroosmoticflow(EOF)andelectrophoreticmobilityofanalyte.Buttherehavebeenonlyafewreportsonthechiralseparationusingpurenonaqueousme…     

Solvent Effects on Aza‐anionic Cycloaromatization of 2‐(2‐Substituted‐ethynyl)benzonitriles

The methanolysis of 2‐(2‐aryl ethynyl)benzonitriles is accelerated when the polar aprotic solvents are added, which could enhance the 6‐endo pathway and give isoquinolones, though the 5‐exo pathway is occupied mostly. The yields of products would also be in creased.     

Tb(III) Speciation in Human Blood Plasma by Computer Simulation

With the wide application of rare earth fertilizer and medicines1, more and more rare earths enter into environment, and also into human body via food chain. Now it is very urgent to study the biological effect of rare earths on human health and environment. After entering into human body by whatever route, lanthanide ions are transported to secondary deposition sites mainly via the plasma in the blood stream. So it is very important to study lanthanides speciation in human blood plasma. Becau…     

Crystallographic report: Diiodo[tris(2‐pyridyl)amine]zinc(II), [(C5H4N)3N]ZnI2

The zinc(II) atom in the molecule of [(C₅H₄N)₃N]ZnI₂ is tetrahedrally coordinated to two nitrogen atoms of the tris(2‐pyridyl)amine ligand and two iodides. The coordination moieties are connected to give a linear structure by intermolecular π–π interactions between the pyridyl rings. Copyright © 2003 John Wiley & Sons, Ltd.     

Preparation and properties of siloxane liquid crystalline elastomers with a mesogenic crosslinking agent

A mesogenic crosslinking agent M-1 was synthesized to minimize the perturbations of non-mesogenic crosslinking agents in liquid crystalline elastomers. The synthesis of new side chain liquid crystalline elastomers containing the rigid mesogenic crosslinking agent M-1 and nematic monomer M-2 by a one-step hydrosilylation reaction is described. The chemical structures of the monomers and network polymers obtained were confirmed by FTIR and ¹H NMR spectroscopy. The mesomorphic properties and phase behaviour were investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The influence of the crosslinking units on phase behaviour is discussed. Liquid crystalline elastomers containing less than 15 mol % of the crosslinking units showed elasticity, reversible phase transitions and a threaded texture. The experimental results demonstrated that the glass transition temperature of polymers P-1-7 increased with increasing concentration of crosslinking agent M-1; but the isotropic temperature and liquid crystalline range decreased slightly.     

Axial magnetic field contacts with nonuniform distributed axial magnetic fields

It is well known that axial magnetic fields (AMFs) can keep vacuum arc in diffuse mode at high current. According to our recent research and other published papers, it has been found that vacuum arc can be maintained in high-current diffuse mode at much higher current if nonuniform AMF is applied, that the axial magnetic field is higher at contact periphery than at center. The influence of spatial distribution of AMF on vacuum arc is mainly studied in this paper. Furthermore, two types of AMF contacts with new structures to generate nonuniform AMF are presented.     

Studies on Micellization of a Polystyrene-b-poly(acrylic acid) Copolymer in Aqueous Media by Pyrene Fluorescence

The aggregation of amphiphilic block copolymers is a crucial phenomenon that controls various applications, and has been extensively treated in the literature1-3. Pyrene is a widely used fluorescence probe for the relative intensities of the vibrational fine structure (five bands) of its fluorescence spectra have been found to be sensitive to the polarity of its environment, the so-called Ham effect4. We report the studies of the aggregation properties of a PS-b-PAA copolymer using pyrene …     

金刚石薄膜的结构特征对薄膜附着性能的影响

在不同实验条件下，用微波等离子体化学气相沉积设备在硬质合金(WC+6%Co)衬底上沉积了 具有不同结构特征的金刚石薄膜.用Raman谱表征薄膜的品质和应力，用压痕实验表征薄膜的 附着性能，考察了薄膜中sp²杂化碳含量、形核密度、薄膜厚度对薄膜附着性能 的影响.结 果表明：sp²杂化碳的缓冲作用使薄膜中sp²杂化碳的含量对薄膜中 残余应力有较大的影 响，从而使薄膜压痕开裂直径统计性地随sp²杂化碳含量的增加而减小；仅仅依 靠超声遗 留的金刚石晶籽提高形核密度并不能有效改变薄膜与硬质合金基体之间的化学结合状况，从 而不能有效提高薄膜在衬底上的附着性能；在薄膜较薄时，晶粒之间没有压应力的存在，开 裂直径并不明显随厚度增加而增加，只有当薄膜厚度增加到一定值，晶粒之间才有较强压应 力存在，开裂直径随厚度的增加而较为迅速地增加. 关键词： 金刚石薄膜 附着性能 2杂化碳')" href="#">sp²杂化碳 成核密度 薄膜厚度