Crystal structure and drawing-induced polymorphism in poly(aryl ether ether ketone). IV

A new crystal modification induced by strain and denoted as form II exists alongside the dominant form I structure in the uniaxially oriented poly(ether ether ketone) (PEEK) and the related polymers. The crystal structure of form II for PEEK is also found to possess a two-chain orthorhombic packing with unit cell parameters of a equal to 0.475 nm, b equal to 1.060 nm, and c equal to 1.086 nm. More extended and flattened chain conformation of form II relative to that of form I is expected to account for an 8% increase in c-axis dimension, which is attributed to the extensional deformation fixed in situ through strain-induced crystallization during uniaxial drawing. Annealing experiments suggest that form II is thermodynamically metastable and can be transformed into more stable form I by chain relaxation and reorganization at elevated temperature without external tension. This strain-induced polymorphism exists universally in the poly(aryl ether ketone) family. (C) 1999 John Wiley & Sons, Inc.

Synthesis of cyclic precursors of poly(ether ether ketone)

A novel synthetic route to cyclic PEEK precursors is described. These new cyclic oligomers have been prepared from hydroquinone and N-phenyl(4,4'-difluorodiphenyl) ketimine. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis unambiguously confirmed the cyclic nature.

Crystallization kinetics of poly(ether ether ketone) (PEEK) from its metastable melt

After isothermal crystallization of the amorphous poly(ether ether ketone), double endothermic behaviour can be found through differential scanning calorimetry experiments. During the heating scan of semicrystalline PEEK, a metastable melt, which comes from the melt of the thinner lamellar crystal populations, can be obtained between these two endotherms. The metastable melt can recrystallize immediately just above the lower melting temperature and form slightly thicker lamellae than the original ones. The thickness and the perfection depend upon the crystallization time and the crystallization temperature. By comparing the TEM morphological observations of the samples before and after partial melting, it can be shown that lamellar crystals, having different thermodynamic stability, form during isothermal crystallization. After partial melting, only the type of lamellar crystal exhibiting the higher thermodynamic stability remains. Wide angle X-ray diffraction measurements shows a slightly change in the crystallinity of the samples before and after the partial melting. Small angle X-ray scattering results exhibit a change in the long period of the lamellar crystals before and after the partial melting process. The crystallization kinetics of the metastable melt can be determined by means of differential scanning calorimetry. The kinetic analysis showed that the isothermal crystallization of the metastable PEEK melt proceeds with an Avrami exponent of n = 1.0 similar to 1.4, reflecting that probably one-dimensional or an irregular line growth of the crystal occurred between the existing main lamellae with heterogeneous nucleation. (C) 1998 Elsevier Science Ltd. All rights reserved.

Synthesis of a new aryl ether ketone polymer

The synthesis of a new aryl ether ketone polymer with an advantageous ratio of glass transition temperature to melting temperature is reported.

Synthesis of novel cyclic aryl ether thioether ketone (Sulfone) oligomers

Two kinds of macrocyclic oligomers containing aromatic sulfide linkages have been synthesized by the solution polycondensation in high yield. The cyclic compounds were characterized by H-1 and C-13 NMR, by and MALDI - TOF MS.

Blends of linear low-density polyethylene and a diblock copolymer of hydrogenated polybutadiene and methyl methacrylate

Blends of linear low-density polyethylene (LLDPE) and a diblock copolymer of hydrogenated polybutadiene and methyl methacrylate [P(HB-b-MMA)] were studied by transimission electron microscope (TEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD). At 10 wt% block copolymer content, block copolymer chains exist as spherical micelles and cylindrical micelles in LLDPE matrix. At 50 wt% block copolymer content, block copolymer chains mainly form cylindrical micelles. The core and corona of micelles consist of PMMA and PHB blocks, respectively. DSC results show that the total enthalpy of crystallization of the blends varies linearly with LLDPE weight percent, indicating no interactions in the crystalline phase. In the blends, no distortion of the unit cell is observed in WAXD tests.

Isothermal and nonisothermal melt crystallization kinetic behavior of poly(aryl ether biphenyl ether ketone ketone): PEDEKK

Isothermal and nonisothermal melt crystallization kinetics of a novel poly(aryl ether ketone), PEDEKK, were investigated by differential scanning calorimetry. Several kinetic analyses were used to describe the crystallization behavior. The activation energies were determined as 425 and 176 KJ/mol for isothermal and nonisothermal crystallization, respectively. The equilibrium melting point T-m(o) was estimated to be 444 degrees C by using the Hoffman-Weeks approach. The observed crystallization characteristics of PEDEKK were compared with those of the other members of the poly(arpl ether ketone) family.

Molecular dynamics simulation of polystyrene-block-poly(methyl methacrylate)

Molecular dynamics is applied to the system of polystyrene-block-poly(methyl methacrylate). The simulation shows that for the block copolymer system, a layered structure, which reflects microphase separation, is obtained and this structure is stable. In order to elucidate that the formation of the layered structure is reasonable, some static properties such as the radial distribution function and the dipole moment are analyzed in some detail.

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 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.

A study of the effect of shell content on the mechanical properties of polycarbonate/poly(butyl acrylate)-cs-poly(methyl methacrylate) blends

The toughening effect of the shell content of a core-shell latex polymer poly(butyl acrylate) (PBA)-cs-poly(methyl methacrylate) (PMMA) on its blends with polycarbonate (PC) was studied. The changes of mechanical properties, morphology, and compatibility of the blends of PC/PBA-cs-PMMA with the change of the shell thickness of PBA-cs-PMMA were investigated. It is interesting to notice that mechanical properties of the blends are very sensitive to the shell thickness (i.e., shell content), and that there is a possibility to adjust the impact and tensile properties of the blend by selecting a PBA-cs-PMMA with a proper core/shell ratio. Hence, a modified PC material with balanced mechanical properties may be prepared.

The synthesis and characterization of the novel poly(aryl ether ketone)s with liquid crystallinity

The novel poly(aryl ether ketone)s with liquid crystallinity were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and substituted hydroquinone with 4,4'-difluorobenzophenone and their thermotropic liquid crystalline properties were characterized by DSC, PLM and WAXD, The copolymers containing 70% biphenol formed nematic phase while the copolymer containing 50% biphenol exhibited smectic texture, The banded textures were formed after shearing the sample in the nematic liquid crystalline state. The identification of the structures in each mesogenic phase has been carried out by combining WAXD with PLM and DSC.

Influence of annealing on structure of poly(aryl ether ether ketone ketone) revealed by SAXS

Structural studies of poly(aryl ether ether ketone ketone) (PEEKK) using small-angle X-ray scattering and one-dimensional electron density correlation function methods revealed that its aggregated state structure was significantly influenced by the annealing temperature. The long period L, the average thickness of the lamellae d, the electron density difference between the crystalline and amorphous regions eta(c) - eta(a), and the invariant Q increased with increasing annealing temperature, but it was opposite to the case of the specific inner surfaces O-s. A transition zone existed between the traditional "two phases" with a dimension about 0.5 nm for semicrystalline PEEKK. (C) 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1829-1835, 1998.