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.

Novel poly(aryl ether ketone)s exhibiting liquid crystallinity

Novel poly(aryl ether ketone)s were synthesized by nucleophilic substitution reactions of difluoromonomer with 4,4'-biphenol and substituted hydroquinone. The results showed that the novel polymers exhibited multiple phase transitions and formed optical birefringence textures above their melting transitions.

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 properties of optically active aromatic polyimides derived from optically pure 1,1'-bi-2-naphthol

A series of new optically active aromatic polyimides containing axially dissymmetric 1,1'-binaphthalene-2,2-diyl units were prepared from optically pure (R)-(+)-or (S)-(-)-2,2'-bis(3,4-dicarboxyphenoxy)-1,1'-binaphthalene dianhydrides and various aromatic diamines via a conventional two-step procedure that included ring-opening polycondensation and chemical cyclodehydration. The optically pure isomer of dianhydride was prepared by a nucleophilic substitution of optically pure (R)-(+)or (S)-(-)1,1'-bi-2-naphthol with 4-nitrophthalonitrile in aprotic polar solvent and subsequent hydrolysis of the resultant tetranitrile derivatives, followed by the dehydration of the corresponding tetracarboxylic acids to obtain the dianhydrides. These polymers were readily soluble in common organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol, etc., and have glass transition temperatures of 251-296 degrees C, and 5% weight loss occurs not lower than 480 degrees C. The specific rotations of the optically active polyimides ranged from +196 degrees to +263 degrees, and the optical stability and chiroptical properties of them were also studied. (C) 1997 John Wiley & Sons, Inc.

Effect of crystal-disrupting chlorohydroquinone on the first-order transitions of poly(aryl ether ketone)s containing biphenyl units

The novel poly(aryl ether ketone)s were synthesized by nucleophilic substitution reactions of 4,4'-difluorobenzophenone with 4,4'-biphenyldiol and chlorohydroquinone. As expected, the copolymers have lower melting transitions than the biphenyldiol-based homopoly(aryl ether ketone) because of the copolymerization effect of the crystal-disrupting monomer chlorohydroquinone. Copolymers containing 50 and 70% biphenyldiol show two first-order transitions which are associated with the crystal-to-liquid crystal transition and the liquid crystal-to-isotropic transition.

Isolation, spectra, structure, and ring-opening polymerization of strained macrocyclic aryl(ether ketone) dimer

Macrocyclic arylene ether ketone dimer was isolated from a mixture of cyclic oligomers obtained by the nucleophilic substitution reaction of bisphenol A and 4,4'-difluorobenzophenone and easily polymerized to high molecular weight linear poly(ether ketone). The cyclic compound was characterized by FTIR, H-1- and C-13-NMR, and single-crystal x-ray diffraction. Analysis of the spectral and crystal structure reveals extreme distortions of he phenyl rings attached to the isopropylidene center and of the turning points of the molecular polygons. The release of the ring strain on ring-opening combined with entropical difference between the linear polymer chain and the more rigid macrocycle at temperatures of polymerization may be the proposed motivating factors in the polymerization of this precursor to high molecular weight poly(ether ketone). (C) 1997 John Wiley & Sons, Inc.

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.

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.

Novel polyaryletherketones containing various pendant groups .1. Synthesis and characterization

Novel high glass transition temperature polyaryletherketones, containing pendant amido, alkyl, and carboxyl groups with reduced viscosity above 0.54 dL/g, were synthesized via solution nucleophilic polycondensation reaction of phenolphthalin, 2',2 ''-diisopropyl-5',5 ''-dimethylphenolphthalin, and 3,3'-bis(4-hydroxyphenyl)isobenzopyrrolidone with bis(4-nitrophenyl)ketone in the presence of potassium carbonate. By ion exchange with Na+ and K+, four ionomers were also prepared. A new monomer simultaneously containing carboxyl and algyl substituents was synthesized by reduction reaction of 2',2 ''-diisopropyl-5',5 ''-dimethyl-phenolphthalein. The resulting polymers were soluble in a few polar aprotic solvents; transparent, colorless, and tough films could easily be cast from DMF or DMSO solution. The mechanical properties of the films were excellent; and their tensile strength, elongation at break, and tensile moduli were in the range of 67.1-97.1 MPa, 7.8-165%, and 1.47-2.27 GPa, respectively. The prepared polymers showed fairly good thermal stability and resonably high glass transition temperatures above 210 degrees C. (C) 1997 John Wiley & Sons, Inc.

The double-melting behavior of poly(ether diphenyl ether ketone)

Poly(ether diphenyl ether ketone) (PEDEK) synthesized by the nucleophilic route has the following chemical structure: [GRAPHICS] At some given temperatures for a given time isothermally crystallized PEDEK sample exhibits two endothermic peaks which are similar to PEEK and PEEKK The melting behavior of PEDEK crystallized from the glassy state is investigated through differential scanning calorimeter (DSC). We consider that the high-melting peak is related to the perfect crystals and the low-melting peak is associated with a few imperfect crystals. (C) 1997 John Wiley & Sons, Inc.

Miscibility of poly(ether ether ketone)/poly(ether diphenyl ether ketone) blends

Poly(ether ether ketone) and poly(ether diphenyl ether ketone) homopolymers are prepared by nucleophilic substitution routes. Miscibility of PEEK/PEDEK blends has been studied by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (d.s.c.). The results indicate that for PEEK/PEDEK blends, when the PEDEK content (weight fraction) is greater than 0.20 and less than 0.75, PEEK and PEDEK components form independent crystalline regions, i.e. they are immiscible; when the PEDEK content is in the range W-PEDEK less than or equal to 0.20 or greater than or equal to 0.75, a rich PEEK- or PEDEK-rich content crystallizes from a mixed melt and PEEK and PEDEK are miscible. Copyright (C) 1996 Elsevier Science Ltd.

Chromatographic separation and C-13 NMR characterization of aromatic diester-diacids isomers

Reverse phase high performance liquid chromatography (HPLC) was used to separate and quantify aromatic diester-diacids isomers which arise from the opening selectivity of anhydride rings towards methanol. C-13 NMR spectroscopy was a supplementary tool to characterize the isomer structure. It was found that a meta-position attack is slightly preferred in pyromellitic dianhydride (PMDA), while the preferred position of an attack in bridged dianhydrides is determined by the chemical nature (donors or accepters) of the bridged group. The stronger its electron-withdrawing abilities, the lower the probability of a meta-position attack.

CHEMICAL-IONIZATION MASS-SPECTROMETRY OF BENZOYL PEROXIDE - A RADICAL AROMATIC-SUBSTITUTION RESULTING IN BIPHENYLCARBOXYLIC ACID IN THE GAS-PHASE

A radical aromatic substitution resulting in biphenylcarboxylic acid is inferred for the decomposition of benzoyl peroxide from the chemical ionization and collision-induced dissociation mass spectra. The thermolysis of benzoyl peroxide gives rise to a benzoyloxy radical, which undergoes rapid decarboxylation and hydrogen abstraction leading to phenyl radical and benzoic acid, respectively. Attack of the resulting phenyl radical on the benzoic acid results in bipbenylcarboxylic acid. On the other hand, the phenyl radical abstracts a hydrogen atom to yield benzene, which is then subjected to the attack of a benzoyloxy radical, affording phenyl benzoate. This substitution reaction rather than the recombination of benzoyloxy and phenyl radicals is found to be responsible for the formation of phenyl benzoate under the present conditions.

APPLICATION OF AN ULTRAMICROELECTRODE IN HOMOGENEOUS CATALYTIC REACTIONS .4. ELECTROCATALYTIC REDUCTION OF ORGANOHALIDES BY METALLOPORPHYRIN AT ULTRAMICROELECTRODE

The electrocatalytic reduction of 1,2-dibromoethane and tetrabromoethane with CoTPP in DMF solutions containing 0.1 M TBAP was investigated at a Pt ultramicroelectrode. The experimental results indicated that CoTPP obviously exhibited catalytic activity for 1,2-dibromoethane and tetrabromoethane. The rate constants of 1,2-dibromoethane and tetrabromoethane in this system were calculated to be 0.14 x 10(3) and 0.5 x 10(2) M-1 S-1, respectively. The reaction mechanism of 1,2-dibromoethane and tetrabromoethane reduction electrocatalysed by CoTPP in 0.1 M TBAP DMF solution is discussed.

Cannibalism in Japanese flounder juveniles, Paralichthys olivaceus, reared under controlled conditions

Laboratory experiments were conducted to determine the effects of sand substratum, light, starvation, fish density and size variation on cannibalism among Japanese flounder juveniles, Paralichthys olivaceus. Cannibalistic behavior (biting and swallowing) increased significantly with starvation except in darkness, where juveniles could not find and attack their prey. Cannibalism occurred more frequently in heterogeneous than in the homogeneous size groups. Cannibalism was more frequent in light than in darkness at each starvation level. With sufficient food present, sand had no significant effect on cannibalism among homogeneous size juveniles, but played an important role in discouraging predation among members of the heterogeneous size groups. With sufficient food present, the rate of cannibalism was generally low and there were no significant differences in cannibalism among fish density levels of the homogeneous juveniles, With starvation, the cannibalism rate was significantly higher in high density groups than in the lower ones. Our results indicate that size variation, starvation and Light are the major factors affecting cannibalism in flounder juveniles, while sand and fish density only have a limited effect on cannibalism, depending on the nature of other factors. (C) 2000 Elsevier Science B.V. All rights reserved.