Part 1. Qualitative comparison between polymer and monomer model compound sulfonation

The sulfonation kinetics of fluorine ended poly(ether ether ketone) (PEEK) in solution in 95.9% and 96.8% concentrated sulfuric acid was studied with the help of a model compound representative of the PEEK chain repeat unit. The reaction rate of the model compound sulfonation was found to be first order with respect to the aromatic ring to be sulfonated. Consequently, PEEK kinetic data were treated following a first order with respect to the unsulfonated repeat unit concentration. Two rate‐slowing effects were detected. They were attributed to ‘long range’ electronic effects resulting from the inductive nature of the fluorine atom, and from the electron‐withdrawing character of the grafted sulfonic acid group. © 2001 Society of Chemical Industry     

The sulfonation of poly(ether ether ketone) as investigated by two‐dimensional FTIR correlation spectroscopy

Fourier transform infrared and two‐dimensional correlation (2D‐COS) spectroscopies were used to follow the structural alteration occurring upon sulfonation of poly(ether ether ketone), in concentrated sulfuric acid at room temperature. With the help of high resolution and high sensitivity 2D‐COS, it was possible to locate the aromatic ring in which the substitution has taken place. Two new IR bands at 1288 and 1320 cm^?1 were attributed to substitution occurring on the aromatic ring flanked with two ether groups. Limited oxidation effects of concentrated sulfuric acid manifested itself by the production of new carbonyl species absorbing in the IR at 1720 and 1750 cm^?1 that were attributed to a fluorenone‐type structure and to ester groups. The 2D‐COS analysis showed that the band at 1470 cm^?1 is not only due to the new substitution by sulfone groups and can not be used in the determination of sulfonation degree. Instead, the intensity of the 1490 cm^?1 band, which can be attributed to skeletal ring vibration, was found to correlate well with the degree of sulfonation calculated from ¹H NMR spectroscopy. The infrared spectroscopy combined with 2D‐COS provides a fast and powerful method for qualitative polymer structure verification and help to establish the quantitative analysis. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41242.     

Part 2. Quantitative interpretation of model compound sulfonation

The mechanism and kinetics of sulfonation of two PEEK model compounds in concentrated sulfuric acid were studied. The first model compound (monomer) is representative of a PEEK repeat unit. The second one is a PEEK dimer. Because both model compounds are fluoroarylketone‐ended, the sulfonation reactions were followed by ¹⁹F NMR. The sulfonation reactions were treated following a first‐order kinetics with respect to the unsulfonated PEEK repeat unit. The comparison between the monomer and dimer results showed two different types of sulfonation behaviour. If only one apparent kinetic constant is considered for monomer sulfonation, two kinetic constants were taken into account to describe the dimer sulfonation process. This is due to a rate slowing effect of a sulfonic acid group on the sulfonation of the adjacent PEEK repeat unit. Furthermore, the results also confirm the rate slowing effect of the fluorine atom on the sulfonation of the neighbouring PEEK repeat unit. © 2001 Society of Chemical Industry     

Synthesis and properties of thio‐containing poly(ether ether ketone)s

A series of thio‐containing poly(ether ether ketone) (PEESK) polymers was synthesized by the introduction of thio groups from 4,4′ thiodiphenol (TDP) into the poly(ether ether ketone) (PEEK) structure via reaction between the phenol and aromatic fluoride groups. The effect of the thio groups on the properties of the PEESK materials was investigated. Differential scanning calorimetry (DSC) analysis and X‐ray diffraction (XRD) patterns show a depression in the crystallinity of the PEESKs with incorporation of the content of thio groups in the backbones. The crystalline structure was identified as an orthorhombic structure with lattice constants of a = 7.52 Å, b = 5.86 Å and c = 10.24 Å for all crystallizable PEESKs. The crystalline structures of the thio‐containing PEEK polymers were the same as that of the neat PEEK, which means the thio‐containing block in the whole thio‐containing PEEK molecule is almost excluded from the crystalline structure and the crystals are completely formed by ‘non‐thio’ blocks only. Due to the glass transition temperature (T_g) and melting temperature (T_m) depression with increase in the TDP content in the reaction system, the processability of the resultant thio‐containing PEEKs could be effectively improved. Copyright © 2004 Society of Chemical Industry     

Part 3. General kinetic model of the sulfonation of PEEK fluoroarylketone chain‐end repeat unit

The sulfonation kinetics of the fluoroarylketone chain‐end repeat unit of PEEK was studied. To achieve this objective, the sulfonation reactions of a trimer, a tetramer and a polymer, each fluoroarylketone ended, were followed by ¹⁹F NMR. A general kinetic model was developed to determine the kinetic constants from ¹⁹F NMR data. The reliability of the kinetic model and of its mathematical expression was ensured. The kinetic constants are then calculated and discussed. In particular, they were compared with the dimer rate constants previously determined. Lastly and as a conclusion of this work, a general kinetic model describing the sulfonation of main chain repeat units of PEEK is proposed. © 2001 Society of Chemical Industry     

Synthesis and properties of sulfonated poly(ether ketone ether sulfone) (S-PEKES) via bisphenol S: effect of sulfonation

Poly(ether ketone ether sulfone) (PEKES) was synthesized by nucleophilic aromatic substitution polycondensation between bisphenol S and 4,4′-difluorobenzophenone (System A), and between bisphenol S and 4,4′-dichlorobenzophenone (System B). Properties of both post-sulfonated polymers are compared with a commercial PEEK 150XF from Victrex^®. The sulfonated polymer samples were characterized by FTIR, ¹H-NMR, TGA, and LCR meter, and the degree of sulfonation (DS) was determined. Advantages of the synthesized PEKES is the better solubility of PEKES in H₂SO₄ relative to PEEK 150XF which results in higher sulfonation degrees, and the S-PEKESs backbones contain the aromatic rings, the carbonyl groups (–C=O) and the sulfone groups (–SO₂–), which promote the chain stiffness and thermal stability. The ion exchange capacity (IEC), the water uptake (%), the dielectric permittivity (ε′), and the electrical conductivity increase monotonically with increasing DS.     

Effect of dihydroxydiphenyl ether on poly(ether ether ketone)

A series of modified poly(ether ether ketone) (PEEK) polymers were synthesized by introduction of addition ether groups from dihydroxydiphenyl ether (DHDE) into the PEEK structure. The inherent viscosity of the DHDE-modified PEEK increased with reaction time at 320 °C. DSC thermograms showed the melting points of the obtained PEEK decreased with the increase of the DHDE content in the backbone. The degradation temperature (T_d) was slightly decreased by the introduction of DHDE. The crystallinity as measured via the X-ray diffraction (XRD) increases with the introduction of DHDE into the modified PEEK. The crystalline structure was identified as an orthorhombic structure with lattice constants a = 7.72 Å, b = 5.86 Å, and c = 10.24 Å. Due to the glass transition temperature (T_g) and the melting temperature (T_m) decreasing with the increase of the DHDE content in the reaction system. the processability of the resultant PEEK could be improved through this DHDE modification.     

Tribological properties of micron silicon carbide filled poly(ether ether ketone)

The composite of poly(ether ether ketone) (PEEK) filled with micron silicon carbide (SiC) with different filler proportions was prepared by compression molding. The friction and wear properties of the composite were investigated at ambient conditions on a block on ring machine by running a plain carbon steel (AISI 1045 steel) ring against the composite block. The morphologies of the worn composite surfaces and the transfer film on the counterpart steel ring were examined with scanning electron microscopy and electron probe microanalysis. The results showed that the friction and wear of PEEK was slightly reduced at a filler proportion of micron SiC of 2.5–5.0 wt %. Abrasive wear was dominant for the PEEK composite; this was especially so at higher filler proportion. Meanwhile, abrasion and transfer to the composite surface of the counterpart steel ring were also observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2611–2615, 1999     

Functionalized poly(ether ether ketone): Improved mechanical property and acellular bioactivity

Poly(ether ether ketone), PEEK, was functionalized by addition of pendant functional groups, that is, acetyl, carboxylic, acyl chloride, amide, and amine groups in the benzene ring of polymer backbone without substituting the parent (ether or ketonic) functional groups of polymer to improve the mechanical and surface adhesivity with acellular inorganic biomaterials. The functional groups of virgin PEEK and functionalized PEEK were identified by Fourier transform infrared spectroscopy and ¹³C nuclear magnetic resonance. The crystallinity was studied by X‐ray diffraction and further supported by differential scanning calorimetry (DSC) analysis. Similarly, the change in glass transition temperature was confirmed by the DSC and dynamic mechanical analysis (DMA). The improved mechanical property was also evaluated by DMA. The excellent surface adhesivity and bioactivity were revealed by acellular in vitro test using simulated body fluid. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Novel copoly(ether ether ketone)s with pendant phenyl groups: synthesis and characterization

In order to obtain poly(ether ether ketone)s having enhanced solubility and processability without extreme loss of other properties, a series of copoly(ether ether ketone)s (Co‐PEEKs) with pendant phenyl groups were synthesized from 1,1‐bi(4‐hydroxyphenyl)‐1‐phenylethane (ph‐BPA), hydroquinone and 4,4′‐difluorobenzophenone via aromatic nucleophilic substitution reaction. The structures and properties of the Co‐PEEKs were characterized using Fourier transform infrared and ¹H NMR spectroscopies, differential scanning calorimetry, thermogravimetric analysis, wide‐angle X‐ray diffraction and solubility testing. These Co‐PEEKs have inherent viscosities in the range 0.14–1.09 dL g^?1, and their number‐average and weight‐average molecular weights reach 72 659 and 163 400 g mol^?1, respectively. The Co‐PEEK with the lowest content of ph‐BPA has a semi‐crystalline nature and is only soluble in 98% sulfuric acid. However, with an increase of ph‐BPA in the Co‐PEEKs, they become amorphous and readily soluble in a wide range of organic solvents and can afford tough films. These Co‐PEEKs have glass transition temperatures of 137–180 °C depending on the content of ph‐BPA. All the Co‐PEEKs have initial degradation temperatures above 480 °C in nitrogen atmosphere. Thus, these Co‐PEEKs with excellent thermal stability, good solubility and processability have potential for use in high‐performance films, coatings, hollow fiber membranes, etc. Copyright © 2011 Society of Chemical Industry     

Spherulitic growth kinetics in miscible blends of poly(ether ether ketone) and poly(ether imide)

Growths of poly(ether ether ketone) (PEEK) spherulites from both pure melt and its miscible blends with poly(ether imide) (PEI) have been studied by polarized optical microscopy. The nucleation density of PEEK spherulites was depressed upon blending with PEI, which can be attributed to the reduction in degree of supercooling arising from equilibrium melting point depression. A modified Lauritzen-Hoffman (L-H) theory was adopted to analyze the growth kinetics. Regime III-II transition was observed with the transition temperature decreasing with increasing PEI composition. Assuming free rotations of the virtual bonds in PEEK molecule, the side surface free energy of 12.0 erg/cm² was calculated from the characteristic ratio. The fold surface free energy of 188 erg/cm² and work of chain folding of 12.3 kcal/mol were then obtained from the modified L-H analysis.     

Fine poly(ether ether ketone) powders

The physical form of polymers is often important for carrying out subsequent processing operations. For example, fine powders are desirable for molding and sintering compounds because they consolidate to produce void free components. The objective of this work is to prepare fine polymeric particulates suitable for processing into fiber reinforced polymer matrix composites. Micron size particles of poly(ether ether ketone) (PEEK) were prepared by rapidly quenching solutions of these materials. PEEK pellets were dissolved at temperatures near the PEEK melting point in a mixture of terphenyls and quaterphenyls; then the solution was quenched to a temperature between the T_g and T_m (≈ 225°C) by adding a room temperature eutectic mixture of diphenyl ether and biphenyl. A supersaturated, metastable solution of PEEK resulted, causing rapid nucleation. Fine PEEK particles rapidly crystallized from this solution. The average particle size was measured using transmission electron microscopy, atomic force microscopy, and by light scattering of aqueous suspensions which had been fractionated by centrifugation. The average particle diameter was about 0.6 μm. Three dimensional photomicrographs obtained via atomic force microscopy showed some aggregates in the suspensions. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1571–1578, 1997     

Synthesis and properties of novel phosphorus‐containing poly(ether ether ketone ketone)s

A novel monomer, bis[4‐(4‐fluorobenzoyl)phenyl]phenylphosphine oxide, was synthesized through the reaction of bis(4‐chloroformylphenyl) phenyl phosphine oxide with fluorobenzene. Three poly(ether ether ketone ketone)s derived from bis[4‐(4‐fluorobenzoyl)phenyl]phenylphosphine oxide and different aromatic bisphenols were prepared by aromatic nucleophilic substitution reactions. The resulting polymers had inherent viscosities in the range of 0.55–0.73 dL/g. The structures of the poly(ether ether ketone ketone)s were characterized with Fourier transform infrared and ¹H‐NMR. Thermal analysis indicated that the glass‐transition temperatures of the poly(ether ether ketone ketone)s were higher than 200°C, and the 5% weight loss temperatures in nitrogen were higher than 463°C. All the polymers showed excellent solubility in polar solvents such as N‐methyl‐2‐pyrrolidone, dimethylformamide, and dimethylacetamide and could also be dissolved in chlorinated methane. The polymers afforded transparent and flexible films by solvent casting. Organic phosphorous moieties also imparted good flame‐retardancy to the polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

复合成盐剂对聚醚醚酮合成与性能的影响

采用4,4′-二氟二苯甲酮、对苯二酚为原料,以不同比例的碳酸钾和碳酸钠为复合成盐剂,二甲苯为脱水剂,二苯砜为溶剂成功制备了一系列聚醚醚酮(PEEK)树脂。通过傅里叶红外光谱和X射线衍射对PEEK树脂结构进行了表征,证明合成的样品是对苯二酚型PEEK树脂。其次,对所制样品分别进行力学性能、特性黏度、热性能测试,详细地探讨不同钾/钠比例的复合成盐剂对PEEK性能的影响。结果表明,所有样品均展示了优异的力学性能和热性能,其熔点和初始分解温度分别大于330℃和520℃,拉伸强度介于77~101 MPa。此外,当碳酸钾和碳酸钠的物质的量比为7∶3时,PEEK树脂的综合性能达到最优。     

Investigation on the crystallization behavior of poly(ether ether ketone)/poly(phenylene sulfide) blends

The morphology of nonisothermally crystallized poly(phenylene sulfide) (PPS) and its blend with poly (ether ether ketone) (PEEK) have been observed by polarized optical microscope (POM) equipped with a hot stage. The nonisothermal crystallization behavior of PPS and PEEK/PPS blend has also been investigated by differential scanning calorimetry (DSC). The maximum crystallization temperature for PEEK/PPS blend is about 15°C higher than that of neat PPS, and the crystallization rate, characterized by half crystallization time, of the PEEK/PPS blend is also higher than that of the neat PPS. These results indicate that the PEEK acts as an effective nucleation agent and greatly accelerates the crystallization rate of PPS. The Ozawa model was used to analyze the nonisothermal crystallization kinetics of PPS and its blends. The Avrami exponent values of neat PPS are higher than that of its blend, which shows that the presence of PEEK changed the nucleation type of PPS from homogeneous nucleation to heterogeneous nucleation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of sulfonated poly(phthalazinone ether sulfone ketone) for ultrafiltration and nanofiltration membranes

Modification of poly(phthalazinone ether sulfone ketone) (PPESK) by sulfonation with concentrated or fuming sulfuric acid as sulfonation agents was carried out to prepare membrane materials with increased hydrophilicity and potentially increased fouling resistance. Sulfonated PPESK (SPPESK) copolymers, with a degree of sulfonation ranging from 10–300%, were prepared and characterized. Factors affecting the sulfonation reaction were studied, and reaction conditions for the preparation of SPPESK with different degrees of sulfonation were determined. Compared with the properties of PPESK, the hydrophilicity of SPPESK was increased, as shown by a reduced contact angle with water. The glass transition temperature was increased from 278°C (PPESK) to a maximum of 323°C for the highly sulfonated derivative, due to the strong polarity of  SO₃H and hydrogen bonding. Ultrafiltration membranes prepared with PPESK and SPPESK were compared. For a SPPESK asymmetric membrane, the PEG12000 rejection was 98% and the water flux was 876 kg · m⁻² · h⁻¹. SPPESK/PPESK composite nanofiltration membranes were also prepared and were shown to have short‐term operational stability up to 120°C. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1685–1692, 2001     

Tribological characteristics of nanometer Si3N4 filled poly(ether ether ketone) under distilled water lubrication

Nanometer Si₃N₄ filled poly(ether ether ketone) (PEEK) composite blocks with different filler proportions were prepared by compression molding. Their friction and wear properties under distilled water lubrication, as well as under ambient dry conditions, were investigated on a block on ring machine by running a plain carbon steel (AISI 1045 steel) ring against the PEEK composite block. The worn surfaces of nanometer Si₃N₄ filled PEEK and the transfer film were observed by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The results showed that distilled water could reduce the friction coefficient of nanometer Si₃N₄ filled PEEK but with the sacrifice of a large reduction in wear resistance. The SEM and EPMA pictures of the worn surfaces indicated that the wear mechanisms of nanometer Si₃N₄ filled PEEK under distilled water lubrication and ambient dry rubbing conditions were different. Under water lubrication, the dominant wear mechanism of the filled PEEK was severe abrasive wear with surface fracture. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1394–1400, 2001     

Permeation resistance of poly(ether ether ketone) to hydrogen,nitrogen, and oxygen gases

We studied the gas permeation properties of poly(ether ether ketone) (PEEK) and compared it with two other polymers commonly used in the construction of semiconductor microenvironments, polycarbonate (PC), and poly(ether imide) (PEI). The PEEK specimens consisted of extruded films as well as compression‐ and injection‐molded specimens. The compression‐molded specimens were prepared to achieve the highest crystallinity. Injection‐molded disks, representing products, were milled to a prescribed thickness. Permeation, diffusion, and solubility coefficients were measured on these various PEEK specimens for hydrogen, nitrogen, and oxygen gases. It was found that PEEK generally has better permeation resistance than PC or PEI; showing up to five times lower permeation rates than PC or PEI, depending on grade, crystallinity, and gas. The superior permeation resistance of injection‐molded or extruded PEEK, when compared with similarly processed PC or PEI, comes from its crystallinity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of honeycomb films from nitryl poly(ether ether ketone)s via water‐droplet templating

The fabrication of honeycomb‐patterned films from nitryl poly(ether ether ketone)s (PEEK‐NO₂) in a high‐humidity atmosphere was reported in this article. PEEK‐NO₂ was prepared through acid (nitric acid and sulfuric acid) nitration from poly(ether ether ketone)s (PEEK). The obtained polymer, which was characterized by Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), and differential scanning calorimetry (DSC) showed excellent solubility and thermal stability. Some influence factors on the pattern formation and the fabrication of the porous structure, such as the solution concentration, the solvent, and the atmosphere humidity, were investigated. The results showed that with the increase of the solution concentration, the aperture of the film diminished gradually; the lower the solvents´ boiling point were, the smaller the films´ apertures were and the more regular the pores´ arrange; only under high‐humidity circumstances could obvious and ordered honeycomb films be formed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structural and mechanical characterization of poly(ether ether ketone) (PEEK) and sulfonated PEEK films: Effects of thermal history,sulfonation, and preparation conditions

In this work, virgin and sulfonated poly(ether ether ketone) films (PEEK and SPEEK, respectively) have been studied by dynamic mechanical analysis, modulated differential scanning calorimetry, wide‐angle X‐ray diffraction, birefringence, and optical microscopy. The properties of the unmodified polymer have been addressed to assess the original morphological characteristics and the changes induced by sulfonation. In general, the introduction of ionic groups in the polymer backbone alters dramatically the intrinsic properties of the parent material. The particular thermomechanical response exhibited by PEEK and SPEEK samples, characterized by a hysteresis loop, can be explained by the reversible and irreversible relaxation–orientation of the microstructure, even in the sub‐T_g region. The results showed that the preparation conditions largely determine the nonequilibrium morphological features of both compression‐molded PEEK films and solvent‐cast SPEEK membranes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 756–774, 2006