A study of the crystallographic equivalence of ether and ketone groups in poly(aryl ether ketone)s

Crystallographic equivalence of ether and ketone in all para-substituted PAEKs crystallized in form I was discussed in this paper. In a word, crystallographic equivalence between ether and ketone groups is tenable when polymer contains only phenyl rings in the repeat unit. If a polymer contains a diphenyl group in the repeat unit, two cases should be distinguished. In the case of PEDEKK and PEEKDK, crystallographic equivalence between ether and ketone linkages is untenable, However, in the case of PEDK and PEDEKDK, crystallographic equivalence between ether and ketone linkages is still tenable.

Gas transport properties of novel cardo poly(aryl ether ketone)s with pendant alkyl groups

Gas transport of hydrogen, oxygen, nitrogen, carbon dioxide, and methane in four cardo poly(aryl ether ketone)s containing different alkyl substituents on the phenyl ring has been examined from 30 to 100 degrees C. The permeability, diffusivity, solubility, and their temperature dependency were studied by correlations with gas shape, size, and critical temperature as well as polymeric structural factors including glass transition, secondary transition, cohesive energy density, and free volume. The bulky, stiff cardo and alkyl groups in tetramethyl-substituted TMPEK-C resulted in increased H-2 permeability (by 55%) and H-2/N-2 permselectivity (by 106%) relative to bisphenol A polysulfone (PSF). Moreover, the weak dependence of gas transport on temperature in TMPEK-C made it maintain high permselectivities (alpha(H2/N2) in 68.3 and alpha(O2/N2) in 5.71) up to 100 degrees C, exhibiting potential for high-temperature gas separation applications.

Isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone)

The isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone) are investigated by differential scanning calorimetry over two temperature regions. The Avrami equation describes the primary stage of isothermal crystallization kinetics with the exponent n approximate to 2 for both melt and cold crystallization. With the Hoffman-Weeks method, the equilibrium melting point is estimated to be 406 degrees C. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter (K-g) of the isothermal melt and cold crystallization is estimated. In addition, the K-g value of the isothermal melt crystallization is compared to those of the other poly(aryl ether ketone)s. (C) 2000 John Wiley & Sons, Inc.

Nonisothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone)

Nonisothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone) (PEKEKK) were investigated by differential scanning calorimetry (DSC). The Avrami equation modified by Jeziorny could only describe the primary stage of nonisothermal crystallization kinetics of PEKEKK. Also, the Ozawa equation could not describe its nonisothermal crystallization behavior. A convenient and reasonable kinetic approach was used to describe the nonisothermal crystallization behavior. The crystallization activation energy were estimated to be -264 and 370 KJ/mol for nonisothermal melt and cold crystallization by the Kissinger method. (C) 2000 John Wiley & Sons, Inc.

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.

Miscibility, crystallization kinetics, and morphology of poly(beta-hydroxybutyrate) and poly(methyl acrylate) blends

The miscibility, spherulite growth kinetics, and morphology of binary blends of poly(beta-hydroxybutyrate) (PHB) and poly(methyl acrylate) (PMA) were studied with differential scanning calorimetry, optical microscopy, and small-angle X-ray scattering (SAXS). As the PMA content increases in the blends, the glass-transition temperature and cold-crystallization temperature increase, but the melting point decreases. The interaction parameter between PHB and PMA, obtained from an analysis of the equilibrium-melting-point depression, is -0.074. The presence of an amorphous PMA component results in a reduction in the rate of spherulite growth of PRE. The radial growth rates of spherulites were analyzed with the Lauritzen-Hoffman model. The spherulites of PHB were volume-filled, indicating the inclusion of PMA within the spherulites. The long period obtained from SAXS increases with increased PMA content, implying that the amorphous PMA is entrapped in the interlamellar region of PHB during the crystallization process of PHB. All the results presented show that PHB and PMA are miscible in the melt. (C) 2000 John Wiley & Sons, Inc.

Crystallization behavior of a novel ether ketone polymer containing meta-phenylene linkage: PEKEKK (T/I)

Nonisothermal and isothermal melt crystallization kinetics of a novel aryl ether ketone polymer containing meta-phenylene linkages, PEKEKK (T/I), were studied by differential scanning calorimetry (DSC). The Avrami equation modified by Jeziorny and a new approach by combining the Avrami equation with the Ozawa equation could describe the nonisothermal crystallization. Isothermal crystallization could also be described by the Avrami equation. The activation energies were 187 and 159 kJ/mol for nonisothermal and isothermal crystallization, respectively. Using the Hoffman-Weeks method, the equilibrium melting point T-m(o) was estimated as 353 degrees C. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter K-g of the isothermal melt crystallization was estimated as 5.49 x 10(5) K-2. The crystallization characteristics of PEKEKK (T/I) were compared with those of all-para PEKEKK. The differences were explained by differences in the chain flexibility of the two polymers.

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 crystallization behavior of poly(ether ether ketone ether ketone) (PEEKEK)

In this paper, the synthesis and crystallization behavior of poly(ether ether ketone ether ketone) (PEEKEK) are reported. PEEKEK was prepared from 4,4'-bis(p-fluorobenzoyl) diphenyl ether (4,4'-FBDE) and hydroquinone along the nucleophilic substitution route. The thermal properties were investigated by using DSC and TGA. The crystallization behavior of PEEKEK under several conditions, i.e., crystallization from the molten state (melt crystallization), crystallization from a quenched sample (cold crystallization) and crystallization induced by exposing glassy sample to methylene chloride (solvent-induced crystallization) has also been investigated. The results show that crystallization of PEEKEK could be induced by the above methods, and no polymorphism was found. The differences in the crystallization of PEEKEK induced by the above methods are seen in their degree of crystallinity.

Synthesis and free-radical ring opening polymerization of macrocyclic aryl thioether ether ketone (sulfone) oligomers

Two kinds of novel macrocyclic aryl thioether ether oligomers were synthesized by nucleophilic condensation reaction in high yields under pseudo-high-dilution condition. A combination of H-1 NMR, GPC and MALDI-TOF MS analyses unambiguously confirmed the cyclic nature and their distributions, Macrocyclic thioether ether ketone oligomers can undergo facile melt ring opening polymerization(ROP) initiated by thiyl radical to give a high molecular weight polymer.

Melt crystallization of poly(ether ether ketone ketone) under strong electric field

In this paper, melt crystallization of poly(ether ether ketone ketone) (PEEKK) under strong electric field was investigated. In the crystal structure of PEEKK, the length of c axis was found to he 1.075 nm, increasing by 7% compared to that of PEEKK crystallized without strong electric field. The molecule chains might take a more extended conformation through the opening of the bridge bond angles by increasing from 124 degrees to 144 degrees under strong electric field in the crystal structure.

Gas-phase ion-molecule reactions of C-60 with the plasma of methyl acrylate

The gas-phase ion-molecule reactions of C-60 with the plasma generated from methyl acrylate under self-chemical ionization conditions were studied by use of a triple-quadrupole mass spectrometer. The adduct cation [C60C3H3O](+) and protonated molecular ion [C60H](+) were observed as the major product ions. The former adduct ion is formed by electrophilic reaction of C-60 with the ion [CH2=CHCO](+), a main fragment ion resulting from the methyl acrylate molecular ion [CH2=CHCOOCH3](+) through alpha cleavage. The latter ion is generated by proton transfer from protonated methyl acrylate to C-60. Semi-empirical quantum chemical calculations have been performed for the eight possible isomers of [C60C3H3O](+) at the Hartree-Fock level by use of the AMI method. The results show three types of cycloadducts as the most stable structures among the possible isomers.

Fabrication of layer-by-layer deposited multilayer films containing DNA and its interaction with methyl green

Multilayer films were fabricated by layer-by-layer electrostatic deposition techniques between poly(diallyIdimethylammonium chloride) (PDDA) and calf thymus DNA (CT DNA) on glassy carbon and quartz substrates. Electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy and UV-vis spectroscopy demonstrated the uniform assembly of PDDA/DNA multilayer films, and X-ray photoelectron spectroscopy confirmed the elemental composition of the films. Moreover, the interaction of DNA in PDDA/DNA films with methyl green was investigated by UV-vis spectroscopy and circular dichroism (CD). (C) 2001 Elsevier Science B.V. All rights reserved.