Physical aging and crystallization of amorphous poly(aryl ether ether ketone ketone)

Physical aging of poly(aryl ether ether ketone ketone) (PEEKK) was investigated. Heat flow responses were measured after annealing the amorphous samples that were obtained by quenching the melt into an ice-water bath at just below the glass transition temperature. Isothermal cold crystallization of the aged samples was carried out. The Avrami equation was used to determine the kinetic parameters, and the Avrami constant it is about 2. An Arrhenius form was used to evaluate the relaxation activation energy of physical aging and the transport activation energy of isothermal crystallization. The activation energy of physical aging was similar in magnitude to that observed for the temperature dependence of crystallization under conditions of transportation control. Results obtained were interpreted as purely kinetic effects associated with the glass formation process. (C) 1998 John Wiley & Sons, Inc.

Synthesis and characterization of poly(amide imide)s containing cyclohexylidene moieties with bulky substituents

Novel poly(amide imide)s (PAI) containing alkyl-substituted cyclohexylidene moieties were synthesized by conventional polycondensation of trimellitic anhydride chloride with novel aromatic diamines followed by chemical imidization using acetic anhydride and pyridine. The inherent viscosities of the resulting PAIs are relatively high and range from 71 to 112 mt g(-1). The prepared PAIs show excellent thermal stability and good solubility. The glass transition temperatures (T-g) measured by DSC are observed in the range of 312-342 degrees C. Furthermore, all the polymers are readily soluble in less hygroscopic organic solvents like cyclohexanone, gamma-butyrolactone as well as aprotic polar solvents.

Miscibility and crystallization behavior of solution-blended PEEK/PI blends

Miscibility and crystallization behavior of solution-blended poly(ether ether ketone)/polyimide (PEEK/PI) blends were investigated by using DSC, optical microscopy and SAXS methods. Two kinds of PIs, YS-30 and PEI-E, which consist of the same diamine but different dianhydrides, were used in this work. The experimental results show that blends of PEEK/YS-30 are miscible over the entire composition range, as all the blends of different compositions exhibit a single glass transition temperature. The crystallization of PEEK was hindered by YS-30 in PEEK/YS-30 blends, of which the dominant morphology is interlamellar. On the other hand, blends of PEEK/PEI-E are immiscible, and the effect of PEI-E on the crystallization behavior of PEEK is weak. The crystallinity of PEEK in the isothermally crystallized PEEK/YS-30 blend specimens decreases with the increase in PI content. But the crystallinity of PEEK in the annealed samples almost keeps unchanged and reaches its maximum value, which is more than 50%. The spherulitic texture of the blends depends on both the blend composition and the molecular structure of the PIs used. The more PI added, the more imperfect the crystalline structure of PEEK. (C) 1998 John Wiley & Sons, Inc.

Crystallization and melting behavior of nylon 66 poly(ether imide) blends

Isothermal crystallization and melting behavior of nylon 66 and its blends with poly(ether imide) (PEI) were investigated by differential scanning calorimetry. Crystallization kinetics such as overall rate constant Z and index n were calculated according to Avrami approach. Crystallization in the blend was retarded with respect to that of pure nylon 66 by incorporation of PEI with high glass transition temperature (T-g). The lowest growth rate of the spherulites was observed in the blends containing 10 and 15 wt% fraction of PEI. A transition temperature where positively birefringent spherulites disappear and negative birefringent spherulites develop was measured by thermal analysis. The transition temperature increased with content of PEI in the blends. A suitable range of isothermally crystallization temperatures, 238.5-246 degrees C, is suggested For determining the equilibrium melting points by means of Hoffman-Weeks approach.

Miscibility and specific interactions in poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) and poly(P-vinylphenol) blends

The blends of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (P(HB-co-HV)/poly(p-vinylphenol)(PVPh) were investigated by differential scanning calorimetry (DSC), Fourier transform IR (FT-IR) spectroscopy and high-resolution solid-state C-13 NMR techniques. Single glass transition temperatures existing in the whole composition range indicates that these blends are miscible. The presence of hydrogen bonding between the hydroxyl of PVPh and carbonyl of P(HB-co-HV), shown by FT-IR spectra, is the origin of the miscibility. Furthermore, results obtained by high-resolution solid-state C-13 NMR give more information about the structure of the blends. (C) 1998 Elsevier Science Ltd. All rights reserved.

Sodium sulfonate-functionalized poly(ether ether ketone)s

A new monomer, sodium 5,5'-carbonylbis(2-fluorobenzenesulfonate) (1), was synthesized by sulfonation of 4,4'-difluorobenzophenone (2) with fuming sulfuric acid. Poly(ether ether ketone)s containing sodium sulfonate groups were synthesized directly via aromatic nucleophilic substitution from the sodium sulfonate-functionalized monomer 1 and Bisphenol A (3) in the presence of potassium carbonate in dimethyl sulfoxide. The polycondensation proceeds without any side reactions. The differential scanning calorimetry measurement indicated that the polymers are amorphous and the glass transition temperatures increase with the content of sodium sulfonate groups in the polymer chain. The degree of substitution with sodium sulfonate groups has strong influence on their thermal stability and solubility.

Study on a comb-like polymer electrolyte based on the backbone of ethylene-maleic anhydride copolymer

A comb-like polymer host(CBPE) as polymer electrolyte was synthesized by reacting poly(ethylene glycol) monomethyl ether (PEGME) with ethylene-maleic anhydride copolymer(EMAC) and endcapping the residual carboxylic acid with methanol. The synthetic process was followed by IR and the amorphous product characterized by IR and elemental analysis. There were two peaks in the plot of the ionic conductivity against Li salt concentration. The plot of log sigma vs. 1/(T - T-0) may exhibit dual VTF behavior when using the glass transition temperature of PEO of side chain as T-0. The comb-like polymer is a white rubbery solid which dissolves in acetone. (C) 1998 Elsevier Science B.V. All rights reserved.

Synthesis and characterization of (phenolphthalein/4,4 '-thiodiphenol) PES copolymers

Copolymers based on monomers phenolphthalein (PP)/4,4'-thiodiphenol (Bis-T)/4,4'-dichlorodiphenylsulfone (DCDPS) were prepared by a route involving the toluene, N-methyl-2-pyrrolidone and anhydrous potassium carbonate synthesis. The range of optimum reaction temperature was between 185 and 195 degrees C. The copolymers were characterized by C-13 NMR, differential scanning calorimetry (DSC) and torsion braid analysis. It was found that all of the copolymers were random and homogeneous and their glass transition temperatures (T-g) decreased linearly with an increase of Bis-T contents in the copolymers. The thermal stability determined by thermogravimetry analysis in air atmosphere indicated that the copolymer had better resistance to thermo-oxidative degradation. Dynamic mechanical measurement showed that (PP/Bis-T) PES copolymers containing 0-50 mol% of Bis-T components had two secondary relaxations. (C) 1998 Elsevier Science Ltd. All rights reserved.

High resolution solid-state NMR and DSC study of poly(ethylene glycol) silicate hybrid materials via sol-gel process

Hybrid materials incorporating poly(ethylene glycol) (PEG) with tetraethoxysilane (TEOS) via a sol-gel process were studied for a wide range of compositions of PEG by DSC and high resolution solid-state C-13- and Si-29-NMR spectroscopy. The results indicate that the microstructure of the hybrid materials and the crystallization behavior of PEG in hybrids strongly depend on the relative content of PEG. With an increasing content of PEG, the microstructure of hybrid materials changes a lot, from intimate mixing to macrophase separation. It is found that the glass transition temperatures (T-g) (around 373 K) of PEG homogeneously embedded in a silica network are much higher than that (about 223 K) of pure PEG and also much higher in melting temperatures T-m (around 323 K) than PEG crystallites in heterogeneous hybrids. Meanwhile, the lower the PEG content, the more perfect the silica network, and the higher the T-g of PEG embedded in hybrids. An extended-chain structure of PEG was supposed to be responsible for the unusually high T-g of PEG. Homogeneous PEG-TEOS hybrids on a molecular level can be obtained provided that the PEG. content in the hybrids is less than 30% by weight. (C) 1998 John Wiley & Sons, Inc.

Studies on biodegradable poly(hexano-6-lactone) fibers 1. Structure and properties of drawn poly(hexano-6-lactone) fibers

Using high molecular weight (M-n=80,000) Poly(hexano-6-lactone) (PCL'), tough and high tenacity PCL monofilaments with various draw ratios (undrawn to 9 times drawn) were prepared by melt-spinning. The relationship between microstructure and properties of the PCL fibers is described in this current IUPAC Technical Report. Analysis of microstructure of the drawn PCL fibers by wide-angle X-ray diffraction revealed typical c-axis orientation with an increase in crystallinity. It was also supported by sonic velocity measurements. The thermal, mechanical, and dynamic mechanical properties of the PCL fibers were affected significantly by draw ratio. DSC thermograms showed that the melting temperature and the enthalpy of fusion increased with draw ratio. The temperature dependence curves of dynamic viscoelasticity showed that the temperature at tan delta peak of alpha dispersion corresponding to the glass transition temperature shifted toward higher temperature and the peak value of tan delta decreased with draw ratio. The dynamic storage modulus and the sonic modulus increased with draw ratio. These results are due to the increase in crystallinity and molecular orientation with drawing, and are responsible for an increase in tensile tenacity as well as knot tenacity of the PCL fibers.

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.

Crystallization kinetics in mixtures of poly(epsilon-caprolactone) and poly(styrene-co-acrylonitrile)

Isothermal crystallization kinetics in the miscible mixtures of poly(epsilon-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) have been investigated as a function of the composition and the crystallization temperature by optical microscopy. The radial growth rates of the spherulites have been described by a kinetic equation including the interaction parameter and the free energy for the formation of secondary crystal nuclei. Fold surface free energies decrease slightly with the increase of SAN content. The experimental findings show that the influence of the glass transition temperature of the mixture, which is related to the chain mobility, on the rate of crystallization predominates over the influence of the surface free energies. This indicates that the glass transition temperature of the mixture should be of more importance, so that the growth rates decrease when the content of the noncrystallizable component increases. In addition, the Flory-Huggins interaction parameter obtained by fitting the kinetic equation with experimental data is questionable.

Synthesis and characterization of soluble polyimides from 1,1-bis(4-aminophenyl)cyclohexane derivatives

A series of novel aromatic diamines (1-3) containing kinked cyclohexylidene moieties was synthesized by a reaction of excess aniline and corresponding methyl-substituted cyclohexanone derivatives. The structures of (1-3) were identifield by H-1 NMR, C-13 NMR, and FT-IR. The polymers were synthesized from the obtained diamines and various aromatic dianhydrides by the conventional polycondensation reaction followed by chemical imidization as well as high-temperature one-step polymerization. The inherent viscosities and weight-average molecular weights of the resulting polyimides were in the ranges of 0.55-1.58 dL/g and (7.4-15.2) x 10(4) g/mol, respectively. The prepared polyimides showed excellent thermal stabilities and good solubility. All polymers were readily soluble in common organic solvents such as tetrahydrofuran, chloroform, tetrachloroethane, etc., and the glass transition temperatures were observed at 290-372 degrees C.

Poly(vinyl methyl ether) poly(methyl methacrylate) blends using diblock copolymer of styrene and methyl methacrylate as compatibilizer

Blends of poly(vinyl methyl ether) (PVME) and poly(methyl methacrylate) (PMMA) compatibilized by poly(styrene-block-methyl methacrylate) (P(S-b-MMA)) ale studied by FT-IR, DSC, excimer fluorescence spectrometry, and scanning electron microscopy (SEM). In FT-IR measurement the ratio of absorption intensity at 1107 cm(-1) to that at 1085 cm(-1) (I-1107/I-1085) reaches a minimum at about 10wt% block copolymer content. DSC results show that the glass transition temperature of PVME in the blends has a maximum at 10 wt% copolymer content. In plots of the ratio of excimer-to-monomer fluorescence emission intensities (I-E/I-M) VS block copolymer content, I-E/I-M increases rapidly above 10%. Ail these phenomena show that PS block chains penetrate into PVME: domains on addition of block copolymer. Above 10% copolymer content, block copolymer chains tend to form micelles in bulk phase.

Permeation of nitrogen and water vapor through sulfonated polyetherethersulfone membrane

The novel polyetherethersulfone (PES-C) prepared from phenol-phthalein in our institute is an amorphous, rigid, tough material with good mechanical properties over a wide temperature range. To improve its water vapor permeability for the application of gas drying, the PES-C was sulfonated with concentrated sulfuric acid and transferred in sodium, cupric, and ferric salt forms. The sulfonation degree can be regulated by controlling the temperature and reaction time. Characterization of sulfonated PES-C in sodium form was made by IR. Some properties of the sulfonated PES-C, such as solubility, glass transition temperature, thermal stability, mechanical properties, and transport properties to nitrogen and water vapor have also been discussed. (C) 1997 John Wiley & Sons, Inc.