New optically active aromatic polyimides II: Synthesis and properties of optically active aromatic polyimide based on (R)-(+)-2,2 '-bis(2-trifluoro-4-aminophenoxy)-1,1 '-binaphthyl

Optically active (R)-(+)-2, 2'-bis(2-trifluoro-4-aminophenoxy)-1, 1'-binaphthyl was prepared from 1, 1'-bi-2-naphthol. The optically active aromatic polyimide was also successfully synthesized. This new polymer has good solubility, thermal stability etc. Its specific rotation was found to be +174 degrees, and its chiroptical property was also studied.

Self-gelatinizable copolymer immobilized glucose biosensor based on Prussian Blue modified graphite electrode

A novel poly(vinyl alcohol) grafting 4-vinylpyridine self-gelatinizable copolymer was adapted to immobilize glucose oxidase. The reduction of hydrogen peroxide (H2O2) was detected at a Prussian Blue (PB) modified graphite electrode. A stable and sensitive glucose amperometric biosensor is described. The copolymer is a good biocompatible polymer in which the glucose oxidase retains high activity. Moreover, the copolymer can adhere firmly to the inorganic PB membrane. The sensor showed an apparent Michaelis-Menten constant of 18 +/- 0.2 mM and a maximum current density of 1.14 mu A cm(-2) mM(-1). The linear range is from 5 mu M to 4.5 mM glucose and the detection limit is 0.5. mu M glucose. The catalytic efficiency of PB for the reduction of H2O2 is higher than that for the oxidation of H2O2. Glucose concentrations in serum samples from healthy persons and diabetic patients were determined using the sensor. The results compared well with those provided by the hospital using a spectroscopy method.

Effect of polymer chain structure and chain distance on luminescent efficiency

Three kinds of PPV-based copolymers were synthesized and characterized. Their luminescent properties were investigated and discussed by PL spectrum, and time-dependence luminescent spectrum in film and solution stare. The results show that in the range of our study, the PL intensity and lifetime of luminescent decay increase with the increasing length of flexible segments and the solution diluting, indicating the tendency of the increase of luminescent efficiency.

Thermodynamics of blends of poly(ethylene oxide) with poly(methyl methacrylate) and poly(vinyl acetate): prediction of miscibility based on Flory solution theory modified by Hamada

Flory solution theory modified by Hamada et al. (Macromolecules, 1980, 13, 729) was used to predict the miscibility of blends of poly(ethylene oxide) with poly(methyl methacrylate) (PEO-aPMMA) and with poly(vinyl acetate) (PEO-PVAc). Interaction parameters of a PEO-aPMMA blend with the weight ratio of PEO/aPMMA = 50/50 at the temperature range of 393-433 K and PEO-PVAc blends with different compositions and temperatures were calculated from the determined equation-of-state parameters based on Flory solution theory modified by Hamada ed al. Results show that interaction parameters of the PEO-aPMMA blend are negative and can be comparable with values obtained from neutron-scattering measurements by Ito et al. (Macromolecules, 1987, 20, 2213). Also, interaction parameters and excess volumes of PEO-PVAc blends are negative and increase with enhancing the content of PEO and the temperature. (C) 1998 Elsevier Science Ltd. All rights reserved.

Phase identification of triphenylene-based discotic monomer and its main chain polymers

A monomer, 2,3,6,7,10,11-hexakispentyloxy triphenylene (HPT) possesses a triphenylene core as a discotic mesogen. Polymers containing this discotic mesogen have been studied using wide-angle X-ray and electron diffraction. HPT is known to show a discotic liquid crystal phase, noted as D-ho (h for hexagonal bidimensional lattice, o for ordered molecular spacing in each column). In this paper, however, HPT Liquid crystalline phases, heated up from the crystalline state and cooled down from the isotropic state, were characterized in the diameter dimensions. In addition. the diameters of the columns are close to a parameter of two separate crystals. A core orientation was, therefore, proposed in the mesophase obtained by heating the crystalline. In order to distinguish these differences, the D-ho phase was divided to include the D-hcd and D-hco phases. Molecular modeling was performed to help our understanding of the orientation. The D-hcd and D-hco phases were used to characterize the phases of the discotic polymeric analogs by comparing their column diameters to those of the monomers. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.

Flexural fatigue behavior of injection-molded composites based on poly(phenylene ether ketone)

Flexural fatigue tests were conducted on injection-molded short fiber composites, carbon fiber/poly(phenylene ether ketone) (PEK-C) and glass fiber/PEK-C (with addition of polyphenylene sulfide for improving adhesion between matrix and fibers), using four-point bending at stress ratio of 0.1. The fatigue behavior of these materials was presented. By comparing the S-N curves and analyzing the fracture surfaces of the two materials, the similarity and difference of the failure mechanisms in the two materials were discussed. It is shown that the flexural fatigue failure of the studied materials is governed by their respective tensile properties. The matrix yielding is main failure mechanism at high stress, while at lower stress the fatigue properties appear fiber and interface dominated. (C) 1997 John Wiley & Sons, Inc.

Liquid crystalline polymer as a processing agent in blends of poly(ether-ketone)/LCP70

Blends of a liquid crystalline thermotropic copolyester (LCP70) and an amorphous phenolphthalein based poly(ether-ketone)(PEK-C) with two viscosities were prepared by melt blending. The blends' morphology, rheological and mechanical properties were investigated by DSC, SEM, mechanical and rheological tests. It was observed that the optimum composition of the PEK-C/LCP70 blend was 10 wt% LCP for both mechanical and rheological properties. When the LCP content was less than 10%, the LCP phase existed as finely dispersed fibrous domains with a diameter of about 1 mu m in the matrix, and both tensile and flexural properties were improved. In contrast, when the LCP content reached 20% or more, the LCP domains coalesced to ellipsoidal particles with a diameter of about 5 mu m, and the mechanical properties decreased as a result. It is demonstrated that pure PEK-C with a high viscosity which was difficult to process by melt extrusion, could be extruded conveniently when 10% LCP70 was incorporated. It is emphasized that LCP not only can be used as a reinforcing phase but also an effective processing agent for engineering thermoplastics, especially for those with high viscosity and narrow processing window. (C) 1997 Elsevier Science Ltd.

Ion-conducting polymers based on modified alternating maleic anhydride copolymer with oligo(oxyethylene) side chains

Comb-like polymers (CPs) based on modified alternating methyl vinyl ether/maleic anhydride copolymer with oligo(oxyethylene) side chains of the type -O(CH2CH2O)(n)CH3 were synthesized and characterized, and complexed with lithium salts to form amorphous polymer electrolytes. Maximum conductivity close to 1.38 x 10(-4) S/cm was achieved at room temperature and at a [Li]/[EO] ratio (EO = ethylene oxide) of about 0.066. The temperature dependence of ionic conductivity suggested that the ion transport was controlled by segmental motion of the polymer, shown by linear curves obtained in Vogel-Tammann-Fulcher plots. The ionic conductivity maximum moved to a higher salt concentration as the temperature increased, indicating that a larger number of charge carriers can be transferred through polymer chains, of which free volume is increased at higher temperature. IR results indicated that the ester in CPs might decompose at 140 degrees C and reproduce the maleic anhydride ring.

The synthesis of a 1,1'-bi-2-naphthol-based bis(ether anhydride) and aromatic polyimides derived therefrom

2,2'-Bis(3,4-dicarboxyphenoxy)-1,1'-binaphthyl dianhydride was used as a new monomer with various aromatic diamines to obtain polyimides by the usual two-step method. The bis(ether anhydride) was prepared by a nucleophilic substitution of I,1'-bi-2-naphthol with N-phenyl-4-chlorophthalimide, N-methyl-4-nitrophthalimide or 4-nitrophthalonitrile in aprotic polar solvent, and subsequent hydrolysis of the resulting bis(ether imide)s or bis(ether dinitrile), and then dehydration of the corresponding tetracarboxylic acid to afford the dianhydride. Most of the obtained polyimides were soluble in chloroform, pyridine, DMF, etc. The polyimide prepared from p-phenylene diamine was partial crystalline, whereas the others showed amorphous patterns in a WAXD study. These polymers have glass transition temperatures between 255-294 degrees C and 5% weight loss temperatures in the range of 502-541 degrees C in nitrogen and 473-537 degrees C in air. (C) 1997 Elsevier Science Ltd.

Study on the two class glass transition and ion transport of a comb polymer electrolyte

The thermal behaviour and ion-transport properties of a comb polymer electrolyte CP350/LiSCN based on methyl vinyl ether/maleic anhydride copolymer with oligo-oxyethylene side chains were studied by means of DSC and ac impedance method. The two glass transition temperatures which can be attributed to side chains and main chains respectively were found to increase with increasing salt concentration. Conductivities which displayed non-Arrhenius behaviour were analyzed by using Vogel-Tammann-Fulcher equation and interpreted on the basis of the configurational entropy model derived by Gibbs and coworkers. The optimum ionic conductivity at 25 degrees C achieved was 2.19x10(-5)S/cm.

Photoluminesence and electroluminescence of the blue emission of devices based on poly(p-phenylenevinylene) copolymers

Bright blue polymer light-emitting diodes have been fabricated by using the poly(p-phenylenevinylene)-based copolymers with 10 C long aliphatic chains as the electroluminescent layers, PBD in PMMA and Alq(3) as the electron-transporting layers, and aluminum as the cathode. The multilayer structure devices show 190 cd/m(2) light-emitting brightness at 460 nm, 15 V turn-on vol- tage. It is found that the intensities of photoluminescence and electroluminescence (EL) increase with increasing aliphatic chain length, the EL intensity and operation stability of these polymer light-emitting diodes can be improved by reasonable design of the structure.

Comblike polymer electrolyte with main chain glass transition near room temperature

A new amorphous comblike polymer (CBP) based on methylvinyl ether/maleic anhydride altering copolymer backbone and on oligooxyethylene side chain was synthesized. The dynamic mechanical properties of CBP and its Li salt complexes were investigated by means of DDV-11-EA type viscoelastic spectrometry. Results showed that there were two glass transitions (alpha-transition and beta-transition) in the temperature range from -100 to 100 degrees C. The beta-transition was assigned to oligo-PEO side chains and the temperature of beta-transition increases with increasing Li salt content. The alpha-transition was assigned to the main chain of CBP. The temperature of the alpha-transition (T-alpha) is also dependent upon the Li-salt content, but not monotonic. The value of T-alpha lies between 30-45 degrees C in the Li salt concentration range studied, near room temperature. It was found that the CBP-Li salt complexes showed an unusual dependence of ionic conductivity on Li salt content. There are two peaks in the plot of the ionic conductivity vs. Li salt concentration, which has been ascribed to the movability of the CBP main chain at ambient temperature. The temperature dependence bf the ionic conductivity indicated that the Arrhenius relationship was not obeyed, and the plot of log sigma against 1/(T - T-0) showed the unusual dual VTF behavior when using side chain glass transition temperature (T-beta) as T-0.

The relation between molecular motion and ion conductivity on a new comblike polymer

A new amorphous comblike polymer(CBP) based on methylvinyl ether/maleic anhydride alternating copolymer backbone and on oligooxyethylene side chain was synthesized The dynamic mechanical properties of CBP-Li salt complexes showed that there were two glass transitions. There are two peaks in the plot of the ionic conductivity vs. Li salt concentration. The plot of Log sigma against 1/(T-To) shows an unusual dual VTF behavior when using sidechain glass transition temperature (T-beta) as To.

X-ray crystallographic structure of cyclic tetramer ester based on bisphenol-A and o-phthaloyldichloride

The polycrystalline powder of the cyclic tetramer ester based on bisphenol-A and o-phthaloyldichloride has been prepared by recrystallization from nitrobenzene and its crystal structure determined by wide-angle X-ray diffraction. The unit cell is orthorhombic and has dimensions a=0.967 nm, b=0.8699 nm, c = 2.0859 nm. With two tetramers per unit cell, the crystal density is 1.36 g cm(-3). Indices of crystal diffraction peaks are also detailed in the present work. Copyright (C) 1996 Elsevier Science Ltd.