Novel macrocyclic precursors of poly{aryl ether ketone (sulfone)} containing hexafluoroisopropylidene units: Synthesis, characterization, and polymerization

Cyclic oligomers containing hexafluoroiso-propylidene(HFIP) units were prepared in excellent yields by a nucleophilic aromatic substitution reaction of 4,4(7)- (hexafluoroisopropylidene) diphenol with difluoro-monomers in the presence of anhydrous potassium carbonate under pseudo high dilution conditions. A combination of GPC, MALDI-TOF MS and NMR analysis confirmed the structure of the cyclic oligomers. All macrocyclic oligomers are crystalline and undergo facile melt polymerization to give high molecular weight fluorinated polyethers.

Formation of a self-assembled monolayer of 2-mercapto-3-n-octylthiophene on gold

Monolayer assembly of 2-mercapto-3-n-octylthiophene (MOT) having a relatively large headgroup onto gold surface from its dilute ethanolic solutions has been investigated by electrochemistry. An electrochemical capacitance measurement on the permeability of the monolayer to aqueous ions, as compared with its alkanethiol counterpart [CH3(CH2)(9)SH (DT)] with a similar molecular length, shows that the self-assembled monolayers (SAMs) of MOT can be penetrated by aqueous ions to some extent. Furthermore, organic molecular probes, such as dopamine, can sufficiently diffuse into the monolayer because a diffusion-limited current peak is observed when the dopamine oxidation reaction takes place, showing that the monolayer is loosely packed or dominated by defects. But the results of electron transfer to aqueous redox probes (including voltammetry in Fe(CN)(6)(3-/4-) solutions and electrochemical ac impedance spectrum) confirm that the monolayer can passivate the gold electrode surface effectively for its very low ratio of pinhole defects. Moreover, a heterogeneous patching process involving addition of the surfactants into the SAMs provides a mixed or hybrid membrane that has superior passivating properties. These studies show that the MOT monolayer on the electrode can provide an excellent barrier for hydrated ionic probe penetration but cannot resist the organic species penetration effectively. The unusual properties of the SAMs are attributed to the entity of the relatively large thiophene moiety between the carbon chain and the thiol group.

Syntheses of novel macrocyclic polyarylate oligomers based on phenolphthalein and m-phthaloyl-dichloride

Novel macrocyclic oligomers were synthesized through the condensation of phenolphthalein and m-phthaloyl-dichloride with triethylamine as catalyst in the mixed solution of methylene chloride and THF via pseudo-high-dilution technique. The oligomers were characterized by IR, H-1 NMR, MS, WAXD, TGA and DSC. It was found that the 3 : 3 adduct (molar ratio of phenolphthalein to m-phthaloyl-dichloride) and the 4 : 4 adduct were the main products and there was a small amount of crystalline in the macrocyclic mixtures. When the mixtures were heated to 360 degrees C, the crystalline disappeared.

Novel macrocyclic aryl thioether ester oligomers: structure characterization and free-radical ring opening polymerization

Novel macrocyclic aryl thioether ester oligomers have been synthesized in high yield from phthaloyl dichloride and 4,4'-thiodiphenol under pseudo high dilution conditions. The cyclic nature was unambiguously confirmed by a combination of MALDI-TOF MS, gel permeation chromatography and NMR analyses. Single-crystal X-ray diffraction of cyclic ester dimer reveals no severe strain on the cyclic structure. The free-radical ring opening polymerization (ROP) of the macrocyclic oligomers was achieved to give high molecular weight polymers via a transthioetherification reaction. The molecular weight of the polymer resulting from ROP decreases as the conversion of cyclic oligomers increases after a polymerization period of 30 min.

Synthesis and crystal structure of a novel butterfly-like complex, [WOS3Cu2(PPh3)(2)(Py)(2)] (Py = pyridine)

A new butterfly-like cluster [WOS3Cu2(PPh3)(2)(Py)(2)] was obtained by reacting [WOS3Cu2(PPb3)(3)] with pyridine. The crystal structure of the cluster has been determined by X-ray diffraction. The compound shows an unusual folded structure, in which two 4-coordinate Cu atoms are bound to the WOS3 moiety via two S-S edges.

Synthesis of cyclic aryl ether sulfone oligomers through interfacial polycondensation method

Novel cyclic aryl ether sulfone oligomers have been synthesized in high yield based on bisphenol A and 4-fluoro-3-nitrophenyl sulfone firstly through interfacial polycondensation reaction under a pseudo-high-dilution condition. Detailed structural characterization of the oligomers by MS, GPC, NMR and IR analyses confirmed the cyclic nature.

Synthesis and polymerization of some macrocyclic (arylene ether sulfone) containing cardo groups and macrocyclic (arylene ether ketone sulfone) oligomers

Some novel macrocyclic (arylene ether sulfone) containing cardo groups and (arylene ether ketone sulfone) oligomers have been synthesized in high yields by a nucleophilic aromatic substitution reaction of 4,4'-difluorophenylsulfone with bisphenols in the presence of anhydrous potassium carbonate under a pseudo-high-dilution condition. Detailed structural characterization of these oligomers by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS), fast atom bombardment mass spectrometry (f.a.b.-m.s.), nuclear magnetic resonance spectrometry (n.m.r.) and single-crystal X-ray structure analysis confirms their cyclic nature, and the composition of the oligomeric mixtures is provided by g.p.c. analysis. Ring polymerization of cyclic oligomers 3a to a high molecular weight polymer with M-w of 59.1 k was achieved by heating at 290 degrees C for 40 min in the presence of a nucleophilic initiator. (C) 1998 Elsevier Science Ltd. All rights reserved.

Macrocyclic oligomeric arylene ether ketones: Synthesis and polymerization

Some novel macrocylic(arylene ether ketone)oligomers were synthesized in high yields by a nucleophilic aromatic substitution reaction of 4,4'-dinitrobenzophenone with bisphenols in the presence of anhydrous potassium carbonate under pseudo-high-dilution conditions. Detailed structural characterization of these oligomers by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS), H-1 NMR and FT-IR confirmed their cyclic nature and the compositions of the oligomeric mixtures was indicated by GPC analysis. Ring-opening polymerization of cyclic oligomers 3a to a high molecular weight polymer with M-w of 52.3 and M-n of 17.2 k was achieved by heating at 280 degrees C for 40 min in the presence of a nucleophilic initiator.

Synthesis of a series of chiral copolymers with azo groups and investigations of reversible liquid crystalline alignment induced by the LB films of these materials

A series of liquid crystalline copolymers, poly{2-hydroxyethyl methacrylate}-co-{6-[4-(S-2-methyl-1-butyloxycarbonylphenylazo)phenoxy]hexyl methacrylate} with an azobenzene moiety as photoreactive mesogenic unit, was prepared and investigated by using DSC, polarized optical microscopy and X-ray diffraction. The results show that these polymers exhibit smectic phases. Z-type Langmuir-Blodgett films of these copolymers were successfully deposited onto calcium fluoride and quartz. Reversible homeotropic and planar liquid crystal alignments were induced by using the photochromism of the LB films of one of the copolymers containing 20.6 mol % of the azo unit.

Gas separation properties of aromatic polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride and 3,5-diaminobenzic acid or its esters

The gas transport properties of a series polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) with 1,3-phenylenediamine or 3,5-diaminobenzic acid (DBA) or its esters are reported. The effects of carboxylic group (-COOH) and carboxylic ether groups (-COOR), at five positions of 1,3-phenylenediamine moiety, on H-2, CO2, O-2, and N-2 permeability, diffusivity, and solubility of the polyetherimides were investigated. The gas permeability, diffusion, and solubility coefficients of the polyetherimides containing COOR are bigger than those of HQDPA-PDA, but the ideal separation factors and ideal diffusivity selectivity factors are much smaller than that of HQDPA-PDA because COOR decreases chain segmental packing efficiency and increases chain segmental mobility. The permeability coefficients of HQDPA-DBA to H-2, CO2, and O-2 are bigger than those of HQDPA-PDA; the ideal separation factors for gas pairs H-2/N-2, CO2/N-2, and O-2/N-2 are also much bigger than those of HQDPA-PDA. Both the diffusion coefficients of CO2 and O-2 and the ideal diffusivity selectivity factors for CO2/N-2 and O-2/N-2 are bigger than those of HQDPA-PDA because COOH decreases both chain segmental packing efficiency and chain segmental mobility. The copolyimides, which were prepared from 3,5-diaminobenzic acid and 3,5-diaminobenzic esters, have both high permeability and high permselectivity. (C) 1997 John Wiley & Sons, Inc.

LIQUID-CRYSTALLINE POLYSURFACTANT

A new kind of amphiphilic polymer(PAMC(16)B) has been synthesized where the amphiphilic moiety is attached as a side chain via the hydrophilic end to the polymer backbone. DSC, POM, and WAXD study revealed that the polysurfactant formed thermotropic liquid crystalline phase. The liquid crystalline domains appeared after annealed at the melt for a period of time, and evolved with annealing. It was indicated that the thermodynamic effect played a significant role on the self-aggregation of hydrophobic ends, so as to form liquid crystalline structure. X-ray investigation suggested that the mesophase structure could be described as smectic with lamellar type of packing, in which alkyl tails aggregated to form layer, A model of supermolecular structure was given.

A NMR-STUDY OF THE INTERACTION OF SILICA WITH DIPALMITOYLPHOSPHATIDYLCHOLINE LIPOSOMES

The interaction of silica with dipalmitoylphosphatidylcholine (DPPC) liposomes has been studied by detecting H-1 and 2D NOESY NMR spectra and measuring proton spin-lattice relaxation time (T-1). The antagonistic effect of aluminium citrate on silica has also been studied by measuring the proton T-1 values, The results show that silica particles mainly bind to the phosphate moiety of the polar headgroup of DPPC bilayers through hydrogen bonds between Si-OH and O-P groups, but they have no significant effect on the conformation of the choline group of the polar headgroup, The addition of silica particles decreases the mobilities of the hydrocarbon chains slightly, Proton T-1 data also indicate that aluminium citrate reduces the effect of silica, A possible mechanism for the toxicity of silica and the antagonistic effect of aluminium titrate on silica is suggested. (C) 1995 Academic Press Inc.

TRIS(TERT-BUTYLCYCLOPENTADIENYL)NEODYMIUM-MU-CHLORO-TRIS(TETRAHYDROFURAN)LITHIUM, [ND(ETA(5)-(T)BUCP)3(MU-CL)LI(THF)3]

The title complex, tris[2(eta5)-tert-butylcyclopentadi-enyl]-mu-chloro-1:2kappa2Cl-tris(tetrahydrofuran-1kappaO)lithiumneodymium, [Nd(C9H13)3(mu-Cl)Li(C4H8O)3], consists of the neutral moiety ((t)BuCp)3Nd linked to the cation [Li(thf)3]+ by a mu-Cl bridge

REDOX THERMODYNAMICS OF CYTOCHROME-C AT THE BARE GLASSY-CARBON ELECTRODE

Investigation of the redox thermodynamics of horse heart cytochrome c at bare glassy carbon electrodes has been performed using cyclic voltammetry with a nonisothermal electrochemical cell. The thermodynamic parameters of the electron-transfer reaction of cytochrome c have been estimated in different component buffer solutions. The change DELTAS(re)-degrees in reaction center entropy and the formal potential E-degrees' (at 25-degrees-C, vs. standard hydrogen electrode (SHE)) for cytochrome c are found to be -64.1 J K-1 mol-1 and 0.251 V in phosphate buffer, -64.8 J K-1 mol-1 and 0.257 V in Tris + HCl buffer, -65.6 J K-1 mol-1 and 0.261 V in Tris+CH3COOH buffer (pH 7.0, ionic strength 100 mM). The temperature dependence of the formal potential obtained in phosphate buffer with or without NaCl in the range 5-55-degrees-C shows biphase characteristics in an alkaline solution with an intersection point at ca. 44-degrees-C or 42-degrees-C, which should be due to a structural change in the protein moiety of cytochrome c. However, in acidic and neutral solutions only a monotonic relationship between E-degrees' and temperature is observed. The effect of the buffer component on E-degrees' for cytochrome c is also discussed.