Self-immobilized metallocene catalysts bearing an allyl group for ethylene polymerization, X-ray crystal structure of [(CH2=CHCH2)CH3Si(C13H8)(2)]ZrCl2

A series of ansa-metallocene complexes with an allyl substituted silane bridge [(CH =CHCH2)CH3Si(C5H4)(2)]TiCl2 (1), [(CH2=CHCH2)CH3Si(C9H6)(2)]MCl2 [M = Ti (2), Zr (3), Hf (4)] and [(CH2=CHCH2)CH3Si(C13H8)(2)]ZrCl2 (6) have been synthesized and characterized. The molecular structure of 6 has been determined by X-ray crystallographic analysis. Complexes 1-4, 6 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization in the presence of MMAO. The results showed that the self-immobilized catalysts 1-4, 6 kept high ethylene polymerization activities of ca. 10(6) g PE mol(-1) M h(-1) and high molecular weight (M-w approximate to 10(5)) of polyethylene.

Synthesis, structure and ethylene polymerization of group 4 complexes with phosphinoamide ligands

Group 4 complexes containing diphosphinoamide ligands [Ph2PNR](2)MCl2 (3: R = Bu-t, M = Ti; 4: R = Bu-t, M = Zr; 5: R = Ph, M = Ti; 6: R = Ph, M = Zr) were prepared by the reaction Of MCl4 (M = Ti; Zr) with the corresponding lithium phosphinoamides in ether or THF. The structure of [(Ph2PNBu)-Bu-t](2)TiCl2 (3) was determined by X-ray crystallography. The phosphinoamides functioned as eta(2)-coordination ligands in the solid state and the Ti-N bond length suggests it is a simple single bond. In the presence of modified methylaluminoxane or i-Bu3Al/Ph3BC(C6F5)(4), catalytic activity of up to 59.5 kg PE/mol cat h bar was observed.

Syntheses and properties of polyimides derived from diamines containing 2,5-disubstituted pyridine group

A Series of novel homo- and copolyimides containing pyridine units were prepared from the heteroaromatic diamines, 2,5-bis (4-aminophenyl) pyridine and 2-(4aminophenyl)-5-aminopyridine, with pyromelltic dianhydride (PMDA), and 3,3',4,4'-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidizaton method. The poly(amic acid) precursors have inherent viscosities of 1.60-9.64 dL/g (c = 0.5 g/dL in DMAC, 30 degrees C) and all of them can be cast and thermally converted into flexible and tough polyimide films. All of the polyimides show excellent thermal stability and mechanical properties. The polyimides have 10% weight loss temperature in the range of 548-598 degrees C in air. The glass transition temperatures of the PMDA-based samples are in the range of 395-438 degrees C, while the BPDA-based polyimides show two glass transition temperatures (T(g)1 and T(g)2), ranging from 268 to 353 degrees C and from 395 to 418 degrees C, respectively. The flexible films possess tensile modulus in the range of 3.42-6.39 GPa, strength in the range of 112-363 MPa and an elongation at break in the range of 1.2-69%. The strong reflection peaks in the wide-angle X-ray diffraction patterns indicate that the polyimides have a high packing density and crystallinity.

Effect of alkyl group length on the conductivity in the 2,3,7,8,12,13,17,18-octakis(alkyl-thio)tetraazaporphyrins and redox properties of the metallooctakis(hexyl-thio)tetraazaporphyrins

A series of 2,3,7,8,12,13,17,18-octakis(alkyl-thio)tetraazaporphyrins (H(2)OATTAP) with different alkyl chain lengths have been synthesized. Cyclic voltammetry and differential pulse voltammetry have been used to investigate the effect of the controlled lengths of the eight peripheral thioether tails on the redox behavior of the molecules. The electrochemical reduction of octakis(hexyl-thio)tetraazaporphyrins, MOHTTAP (where M = Cu, Ni), was studied in 1,2-dichloroethane at a platinum electrode. The Cu derivative was oxidized in one single-electron-transfer step to yield a pi-cation radical and reduced in three single-electron-transfer steps to yield a pi-anion radical, dianion and trianion, respectively. For the Ni derivative, electron transfer reactions involving both the central metal atom and the macrocyclic ring were observed. Electron transfer pathways are proposed based upon voltammetric and in situ spectroelectrochemical results.

The study on automorphism group of ESESOC

It is necessary to generate the automorphism group of a chemical graph in computer-aided structure elucidation. In this paper, an algorithm was developed by the all-paths topological symmetry algorithm to build the automorphism group of a chemical graph. A comparison of several topological symmetry algorithms reveals that the all-paths algorithm (APA) could yield the correct class of a chemical graph. It lays a foundation for the ESESOC system in computer-aided structure elucidation.

Aggregation behavior of amphiphilic D-pi-A molecules bearing recognition group

Aggregation behavior of two amphiphilic D-pi -A molecules bearing barbituric acid as both recogniton group and electron-drawing substituent, 5-(4-dodecyl oxybenzylidene)-(1H, 3H)-2,4,6-pyrimidine trione (PB12) and 5-(4-N,N-didodecyl aminobenzylidene)-(1H,3H)-2,4,6-pyrimidine trione (AB(12)) was studied by UV-visible, fluorescence, and surface voltaic spectroscopies (SPS). The experimental results indicate that PB12 tends to form J-aggregate and AB(12) tends to form H-aggregate under increasing concentration. An intramolecular twisted charge transfer (TICT) emission around 500 nm is observed when J-aggregate is formed between PB12 molecules, and an excimer emission around 600 nm is observed when H-aggregate is formed between AB(12) molecules.

Automorphism group algorithm in computer-aided structure elucidation

It is necessary to generate automorphism group of chemical graph in computer-aided structure eluciation. In this paper, an algorithm is developed by all-path topological symmetry algorithm to build automorphism group of chemical graph. A comparison of several topological symmetry algorithm reveals that all-path algorthm can yield correct of class of chemical graph. It lays a foundation for ESESOC system for computer-aided structure elucidation.

Synthesis and properties of three novel series of monomers containing para-methoxyazobenzene as the mesogenic group

Three novel series of monomers, namely n-1-bromo-[4-(4-methoxyphenylazo)phenyloxy]-alkanes (Bn, n = 3, 6, 10), n-[4-(4-methoxyphenylazo) phenyloxy]alkyloxy-4-methoxybenzene (Cn, n = 3, 6, 10) and n-[4-(4-methoxyphenylazo)phenyloxyl]alkyloxy-[4-methoxy-2,5-bis-(chloromethyl)] benzene (Dn, n = 3, 6, 10) were synthesized and characterized with FTIR, H-1 NMR, UV-visible and fluorescence spectroscopy. Their thermal behaviour was studied by different scanning calorimetry and polarizing optical microscopy. The results show that B3, B6 and C6 exhibit monotropic nematic liquid crystalline behaviour.

The single crystal-like banded textures in the films of a thermotropic liquid crystalline poly(aryl ether ketone) containing a lateral chloro group

The banded textures in the films of a thermotropic liquid crystalline poly(aryl ether ketone) containing a lateral chloro group have been studied by means of transmission electron microscopy(TEM), electron diffraction(ED) and atomic force microscopy (AFM). The crystallization-induced Landed texture without external shear can be formed when the thin films were annealed at the temperature range(320-330 degrees C) of the liquid crystalline state from the melt, The results show that the banded regions have high orientation of single crystal based on the orthorhombic packing and the growing direction of the Lands is along the b axis of the crystals, This kind of single crystal-like bands is due to the different orientation of the packing molecular chains, The molecular chains of the dark bands in the bright field electron micrograph are perpendicular to the film plane, while the ones of the bright Lands are tilt along the b axis with the tilt angle upto +/-20 degrees.

Synthesis and thermotropic liquid crystalline behaviour of novel poly(aryl ether ketone)s with a lateral methoxy group

Novel poly(aryl ether ketone)s containing a lateral methoxy group were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and methoxyhydroquinone with 1,4-bis(4-fluorobenzoyl)benzene in a sulfolane solvent in the presence of anhydrous potassium carbonate. Their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques, e.g. differential scanning calorimetry (DSC), polarized light microscopy and temperature-dependent FTIR. Thermotropic liquid crystalline behaviour was observed in the copolymers containing 30-80 mol-% mexthoxyhydroquinone. Both melting (T-m) and isotropization (T-i) transitions appeared in the DSC curves. The polarized light microscopy study of the liquid crystalline copolymers suggested their ordered smectic structures. As expected, the copolymers had lower melting transitions than the biphenol-based homopoly(aryl ether ketone)s because of the copolymerization effect of the crystal-disrupting monomer methoxyhydroquinone.

Synthesis and characterization of side chain liquid crystal M5MPP/MMEANB copolymers containing NLO active group

A new series of side chain liquid crystal polymers based on the backbone of polymethacrylate containing 4-nitroazobenzene and 4-methoxybiphenyl group as side chain mesogen were prepared and characterized, FTIR, H-1 NMR, POM and WAXD were used to study the structure, phase behavior and mesophase texture of this series of SCLC copolymers. The researches show that polymer PM5MPP and copolymer M5MPP/MMEANB are enantiotropic liquid crystalline polymers, but polymer PMMEANB has no liquid crystalline properties. DSC results showed that the thermal stability of the mesophase of this series of copolymers was enhanced by the existence of intermolecular electron donor-acceptor interaction. It was found that the temperature range of the mesophase of the copolymers was broadened with increasing 4-nitroazobenzene units. The focal-conic texture observed by POM indicated that this series of the copolymers possessed the characteristics of smectic liquid crystal.

The synthesis and thermotropic liquid crystalline behaviour of novel main chain poly(aryl ether ketone)s containing a lateral phenyl group

Novel main chain poly(aryl ether ketone)s containing a lateral phenyl group were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and phenylhydroquinone with either 4,4'-difluorobenzophenone or 1,4-bis(4-fluorobenzoyl)benzene and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. Thermotropic liquid crystalline behaviour was observed in the copolymers containing 50 and 70mol% biphenol. Melting (T-m) and isotropization (T-i) transitions both appeared on the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline nematic state. As expected, each of the copolymers had a relatively lower melting transition than the biphenol-based homopoly(aryl ether ketone)s because of the copolymerization effect of the crystal-disrupting monomer phenylhydroquinone.

Synthesis and investigation of monoesters of polymaleic acids with azo-group

A series of amphiphilic polymers, monoesters of polymaleic acid containing ate-side groups (PMAN-A(n)Me) was synthesized by the reaction of alcohol(A,Me) with polymaleic anhydride (PMAN) for Langmuir-Blodgett assembly. The effects of the length of flexible spacer in the side chain on the pi-A isotherms and LB films were investigated. The UV-Vis and infrared linear dichroism spectra showed that the ate-side groups were highly oriented in PMAN-A(6)Me LB film deposited on silica or CaF2 substrate.

The synthesis and thermotropic liquid crystalline behavior of the novel poly(aryl ether ketone)s containing chloro-side group

The novel poly(aryl ether ketone)s containing chloro-side group were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and chlorohydroquinone with either 4,4'-difluorobenzophenone(BP/CH/DF) or 1,4-bis(p-fluorobenzoyl)benzene (BP/CH/BF) and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. The thermotropic liquid crystalline behavior was observed in the copolymers containing 50 and 70% biphenol. Melting transition (Tm) and isotropization transition (Ti) both appeared in the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline state. The novel poly(aryl ether ketone)s had relatively higher glass transition temperature (Tg) in the range of 168 similar to 200 degrees C and lower melting temperature (Tm) in the range of 290 similar to 340 degrees C. The thermal stability (Td) was in the range of 430 similar to 490 degrees C.