Synthesis of polyphenylene ether and thioether ketones

The known polymerization of 4,4′-difluorobenzophenone (DFB) with the dianion of hydroquinone to poly(phenylene ether ether ketone) (PEEK) and polymerization of either DFB with the dianion of 4,4′-dihydroxybenzophenone or self polycondensation of the anion of 4-hydroxy-4′-fluoro-benzophenone to poly(phenylene ether ketone) (PEK) were studied in N-cyclohexyl-2-pyrrolidone (CHP), which is a high-boiling aprotic polar solvent. The formation of high-molecular weight PEEK and PEK in this solvent was very efficient. The reactivity in CHP can be ascribed to effective solvation of metal ions rendering the anion very reactive toward nucleophilic substitution. The polymerization was extended to 4,4′-bis(4-fluorobenzoyl)diphenyl ether and 1,4-bis[4-(4-fluorobenzoyl)phenoxy]benzene to give a high molecular weight polymer with PEK and PEEK repeating units and PEEK respectively. The polymerization of DFB with purified anhydrous sodium sulfide in CHP gave rapidly a high molecular weight poly(phenylene ketone sulfide) (PKS). In contrast, diphenyl sulfone (DPS) was not very effective in obtaining such a high molecular weight PKS even with prolonged heating, which suggests the uniqueness of CHP in promoting a high degree of polymerization.     

Surface Heparinization of Poly(ether ether ketone)

Photo-grafting of hydrophilic monomer and space arms was used to enhance the hydrophilicity of poly(ether ether ketone)(PEEK) with the aim of extending its application to biological fields. PEEK films were surface modified by UV grafting of acrylic acid(AA) to introduce ―COOH on PEEK surface. Adipic amine was used as a space arm to introduce heparin on PEEK surface based on the condensation reaction between ―NH₂ and ―COOH. The modified PEEK(PEEK-COOH, PEEK-NH₂ and PEEK-Hep) was characterized by energy-disperse spectroscopy (EDS), X-ray photoelectron spectroscopy(XPS) and water contact angle measurements, which show that heparin was grafted on PEEK surface. The contact angles of modified PEEK films were lower than those of original films, demonstrating a significant improvement of surface hydrophilicity.     

Non-isothermal crystallization kinetics of continuous glass fiber-reinforced poly(ether ether ketone) composites

Current studies on crystallization kinetics for glass fiber-reinforced poly(ether ether ketone) mainly focused on short glass fiber-reinforced composites and their isothermal crystallization. It is worth noting that continuous glass fiber-reinforced poly(ether ether ketone) composite (CGF/PEEK) possesses relatively higher mechanical performance than short fiber-reinforced PEEK under high temperature. Here, for the first time, we investigate the non-isothermal crystallization kinetics and melting behavior of CGF/PEEK by differential scanning calorimetry at four different cooling rates. By evaluating the crystallite size of CGF/PEEK using X-ray diffraction, it is found that with the decreasing cooling rate, the crystallite size distribution evolves more uniform, and the size of crystallites enlarges. Besides, by systematical analysis, we find the modified Avrami equation can well describe crystallization behavior of the CGF/PEEK. The higher Avrami value of CGF/PEEK than pure PEEK indicates that CGF could introduce a more complex geometry effect on the crystallization. The addition of CGF greatly reduces the absolute value of crystallization activation energy of PEEK, suggesting that CGF can reduce the nucleation energy barrier. The obtained results illustrate that CGF can accelerate the nucleation rate due to heterogeneous nucleation while reduce the growth rate due to retarded polymer chain mobility. And the cooling conditions can influence crystal growth and morphology.

     

Sulfonated poly(ether ether ketone)/polyaniline composite proton-exchange membrane

Sulfonated poly(ether ether ketone) (PEEK) was prepared by sulfonation of commercial Victrex^@ PEEK and degree of sulfonation was found to be about 44.5% by ¹H NMR. Sulfonated PEEK/polyaniline composite membranes, in order to prevent methanol crossover, were prepared by chemical polymerization of a thin layer of polyaniline (PANI) in the presence of a high oxidant concentration on a single face modification. FTIR and PANI coating density studies confirmed the loading of PANI in sulfonated PEEK membrane matrix. PANI composite membranes with different polymerization time were prepared and subjected to thermogravimetric analysis as well as electrochemical and methanol permeability study to compare with sulfonated PEEK and Nafion 117 membrane. Ion-exchange capacity, water uptake, proton transport numbers and proton conductivities for different PANI composite sulfonated PEEK (SPEEK) membranes were found to be dependent on the coating density of the PANI in the membrane matrix and were slightly lower than that of Nafion 117 membrane. Methanol permeability of these membranes (especially SPEEK/PANI-1.5) was about four times lower than Nafion 117 membrane. Among the all SPEEK membranes synthesized in this study, SPEEK-1.5 appears to be more suitable for direct methanol fuel cell (DMFC) application considering optimum physicochemical and electrochemical properties, thermal stability as well as very low methanol permeability. Above all, the cost-effective and simple fabrication technique involved in the synthesis of such composite membranes makes their applicability quite attractive.     

聚醚醚酮表面的亲水改性和胶原蛋白固定化

采用紫外光接枝法对聚醚醚酮(PEEK)表面进行化学修饰和生物分子固定化.首先向PEEK表面引入亲水性的丙烯酰胺,并以此为反应位点通过戊二醛将胶原和胶原蛋白固定在PEEK表面.用接触角测定仪、扫描电镜、荧光标记和X射线光电子能谱等对改性薄膜进行了表征.结果表明,PEEK上丙烯酰胺的接枝密度高达50.9μg/cm~2;改性薄膜表面浸润性显著提高,水接触角最低降至(22±3)°.荧光标记胶原固定的PEEK薄膜荧光发射光谱强度最高,并在X射线光电子能谱中检测到N元素,表明胶原已固定化,固定胶原蛋白的浓度为10.2μg/cm~2.     

Surface Plasticization of Poly(ether ether ketone)

This paper describes a study of the surface plasticization and antiplasticization of an amorphous and a semicrystalline poly(ether ether ketone) (PEEK) in solvent environments using nanohardness method. A range of solvents (octane, chloroform, tetrachloroethane, acetone, dichlorobenzene, polyethyleneglycol (PEG), methanol and water) based on the Hilderbrand’s Solubility Parameter were selected as solvent environments. The results of the nanoindentation hardness experiments performed on the virgin and the solvent immersed polymeric surfaces are reported. The surface plasticization or antiplasticization is reported on the basis of the softening or the hardening of the near surface layers (?1 μm) after immersion of the polymeric surfaces in the solvent environments. Surface plasticization of the amorphous PEEK has been observed in organic solvents. The chlorine containing solvents have severely degraded the hardness of the amorphous polymer. A surface hardening of the amorphous PEEK has been observed after immersion in water. Semicrystalline PEEK was seen to exhibit a considerable inert behaviour to common organic solvents but chlorinated organic solvents and water have caused a decrease in the surface mechanical properties.     

聚醚醚酮/聚醚醚酮酮共混体系的熔融和等温结晶行为

采用熔融共混方法制备了聚醚醚酮和聚醚醚酮酮的共混物,用DSC对共混物的熔融行为和等温结晶行为进行了研究.结果表明,共混物熔点随聚醚醚酮含量增加而降低,但与聚醚醚酮酮有相同的平衡熔点,二者共混没有改变其结晶的成核与生长机制.     

Immobilization of Bovine Serum Albumin on Poly(ether ether ketone)for Surface Biocompatibility Improvement

UV-induced graft polymerization of acrylic acid(AA)on poly(ether ether ketone)(PEEK)films was carried out to introduce-COOH for the subsequent immobilization of bovine serum albumin(BSA).BSA was introd...     

Synthesis and Characterization of Poly(ether ether ketone)s with (2,5‐dihydroxy)phenyl Side Group

A new monomer, (2,5‐dimethoxy)phenylhydroquinone (DMPH), was prepared in a two‐step synthetic procedure. One aromatic poly(ether ether ketone)s with 2,5‐dimethoxy phenyl side group (DMP‐PEEK) was synthesized via an aromatic nucleophilic substitution reaction with 4,4′‐difluorobenzophenone (DFB). Poly(ether ether ketone)s with 2,5‐dihydroxy phenyl side group (DHP‐PEEK) was obtained via hydrolysis of methoxy group on the DMP‐PEEK. Both of the high molecular weight polymers could be obtained despite the steric effect of the bulky pendant groups. The two polymers have good solubility at room temperature.     

Dynamic relaxation behavior of solvent-crystallized poly(ether ether ketone)

The dynamic relaxation behavior of solvent-crystallized poly(ether ether ketone) (PEEK) has been investigated in the region of the glass-rubber (α) relaxation using dynamic mechanical and dielectric methods. Amorphous PEEK films were exposed to saturated methylene chloride and acetone vapor, with solvent-induced crystallization observed for both penetrants. Sample desorption at elevated temperatures (under vacuum) resulted in virtually complete removal of residual penetrant, thus providing for the measurement of relaxation characteristics independent of plasticization. Both dynamic mechanical and dielectric studies indicated a marked positive offset in the isochronal relaxation temperatures of the solvent-crystallized samples relative to thermally crystallized specimens of comparable bulk crystallinity, and a higher apparent activation energy in the solvent-crystallized case. These results are consistent with the evolution of a tighter crystalline morphology (i.e., smaller crystal long spacing) in the solvent-crystallized samples, the crystallites imposing a greater degree of constraint on the long-range motions of the amorphous chains inherent to the glass-rubber relaxation. © 1994 John Wiley & Sons, Inc.     

UV-induced Self-initiated Graft Polymerization of Acrylamide onto Poly(ether ether ketone)

Photo-grafting of hydrophilic monomer was used to enhance the hydrophilicity of poly(ether ether ketone) (PEEK) with the aim of extending its applications to biological fields. PEEK sheets were surface modified by grafting of acrylamide(AAm) with ultraviolet(UV) irradiation in the presence or absence of benzophenone(BP). The effects of BP, irradiation time and monomer concentration on the surface wettability of PEEK were investigated. Characterization of modified PEEK using scanning electron microscopy(SEM), energy-disperse spectrometer(EDS) and water contact angle measurements shows that AAm was successfully grafted on PEEK surface both in presence and absence of BP. With the increase in irradiation time and monomer concentration, contact angles decrease to as low as 30°, demonstrating a significant improvement of surface hydrophilicity. In agreement with the decrease in contact angle, under identical conditions, the nitrogen concentration increases, suggesting the increase in grafting degree of the grafting polymerization. This investigation demonstrates a self-initiation of PEEK due to its BP-like structure in the backbone of the polymer. Though the graft polymerization proceeds more readily in the presence of BP, the self-initiated graft polymerization is clearly observed.     

原子转移自由基聚合法制备侧链型磺化聚醚醚酮阳离子交换膜

以二氟二苯甲酮、双酚A和邻甲基氢醌为单体先经缩聚反应生成聚醚醚酮(PEEK),PEEK经修饰合成含有溴异丙基侧基的聚醚醚酮,以此为原子转移自由基聚合(ATRP)大分子引发剂,通过ATRP法聚合,在PEEK主链上接枝引入聚苯乙烯磺酸钠侧链,得到侧链型PEEK接枝聚合物(PEEK-g-StSO3Na)。 用傅里叶变换红外(FTIR) 光谱、核磁共振氢谱(1H NMR)、热重分析(TG)和扫描电子显微镜(SEM)等技术手段对PEEK-g-StSO3Na的结构进行表征。 结果表明,苯乙烯磺酸钠成功的被接枝到聚醚醚酮主链上,PEEK-g-StSO3Na膜具有明显的亲水疏水微相分离结构,磺酸基团相互聚集形成离子通道,离子交换容量为2.034 mmol/g的PEEK-g-StSO3Na膜的电导率为8.34×10-2 S/cm,膜的尺寸稳定性优于Nafion 117。     

Evaluation of Stabilization Performances of Antioxidants in Poly(ether ether ketone)

Two types of antioxidants(a primary antioxidant and a secondary antioxidant) were used to improve the stability of poly(ether ether ketone)(PEEK). The effects of the antioxidants on the properties of PEEK and the stabilization mechanism were investigated by some characterization methods, such as rheometer, thermogravimetric ana- lysis(TGA), universal tester and electron spin resonance(ESR). The results indicate that the efficiency of the phosphorous antioxidant(DS) in improving the stability of PEEK was better than that of the phenolic antioxidant(DN) in both melting stability and thermal stability, and the thermal stability of PEEK sample containing 0.07%(mass fraction) DS was the best among all the samples due to the decrease of the free radicals density, as proven by ESR measurement. Additionally, no obvious changes could be observed in mechanical properties of PEEK containing antioxidants compared to those of virgin PEEK.     

A Fourier transform Raman spectroscopy study of the crystallization behaviour of poly (ether ether ketone)/poly (ether imide) blends

This paper describes a study of the crystallization behaviour of blends consisting of the polymers poly (ether ether ketone) (PEEK) and poly (ether imide) (PEI) using Fourier transform Raman spectroscopy. The annealing process of PEEK was followed for the virgin polymer and also when it was blended with PEI. The data presented show that the crystallization process of PEEK is inhibited by the presence of the PEI, but the extent of the crystallinity is increased. There is also evidence that the presence of the PEI induces premelting of the PEEK.     

Miscible blends of modified poly(aryl ether ketones) with aromatic polyimides

The phase behavior of binary blends of poly(ether ether ketone) (PEEK), sulfonated PEEK, and sulfamidated PEEK with aromatic polyimides is reported. PEEK was determined to be immiscible with a poly(amide imide) (TORLON 4000T). Blends of sulfonated and sulfamidated PEEK with this poly(amide imide), however, are reported here to be miscible in all proportions. Blends of sulfonated PEEK and a poly(ether imide) (ULTEM 1000) are also reported to be miscible. Spectroscopic investigations of the intermolecular interactions suggest that formation of electron donoracceptor complexes between the sulfonated/sulfamidated phenylene rings of the PEEKs and the n-phenylene units of the polyimides are responsible for this miscibility. © 1993 John Wiley & Sons, Inc.     

Effect of Antioxidants on the Stability of Poly(ether ether ketone) and the Investigation on the Effect Mechanism of the Antioxidants to Poly(ether ether ketone)

Two types of antioxidants (a phenolic antioxidant and a phosphorous antioxidant) were used to improve the stability of poly (ether ether ketone) (PEEK). To evaluate the effect of the antioxidants on the properties of PEEK and the stabilization mechanism, some characterization methods were carried out, such as rheometer, TGA, and electron spin resonance (ESR). The results indicated that the efficiency of the phosphorous antioxidant (DS) in improving the stability of PEEK was better than that of the phenolic antioxidant (DN) and the thermal stability of PEEK sample containing 0.07 wt% DS was the best among all samples due to the decrease of the free radicals density, as proven by ESR measurement. The possible stabilization mechanism of the antioxidants to PEEK was proposed to reveal the reason that caused the different performances of the two types of antioxidants to PEEK.     

Melting behavior of poly(ether ether ketone) in its blends with poly(ether imide)

We detail the melting behavior of poly(ether ether ketone) (PEEK) and investigate its melting behavior in miscible blends with poly(ether imide) (PEI). The determination of the equilibrium melting point (T_m⁰) of PEEK is discussed by considering its inhomogeneous morphology. T_m⁰ is obtained by a long extrapolation of a Hoffman–Weeks plot to 384°C. Hindrance of PEEK crystal reorganization induced by PEI during heating is observed over the blend composition investigated (20–75 wt % PEEK). This behavior is correlated with the incorporation of PEI in the interlamellar zones of PEEK crystals. The interaction parameter χ of PEEK/PEI blends is estimated by the equilibrium melting point depression. This gives the interaction density B = ?1.2 cal/cm³, and x = ?0.40 at 400°C. © 1993 John Wiley & Sons, Inc.     

A Fourier transform Raman spectroscopy study of poly (ether ether ketone)/polytetrafluoroethylene (PEEK/PTFE) blends

A study of blends consisting of the polymers poly (ether ether ketone) (PEEK) and polytetrafluoroethylene (PTFE) using Fourier transform Raman spectroscopy is described. The data presented show that the presence of PTFE in the PEEK environment causes the PEEK molecules to become more ordered. The most significant changes to the PEEK molecules are shown to occur with only small additions of PTFE. These observations are compared with reported frictional and hardness data.     

Synthesis and properties of poly(ether ether ketone)-block-sulfonated polybutadiene copolymers for PEM applications

A novel series of sulfonated block copolymers were successfully synthesized by the condensation of modified poly(ether ether ketone) (PEEK) and polybutadiene (PB), followed by the selective post-sulfonation of PB blocks using acetyl sulfate as the sulfonating reagent. The sulfonic acid groups were only attached onto PB segments due to the high reactivity of double bonds to sulfonating reagent. The degree of sulfonation was controlled by changing the feed ratio of sulfonating reagent to block copolymer. PEEK-b-sPB could be easily cast into flexible and transparent membranes. The obtained membranes exhibited good thermal stability and satisfied mechanical properties. Tensile test showed the incorporation of sulfonate groups into PB blocks resulted in an increase in tensile strength and a decrease in elongation at break. TEM images revealed the existence of ionic spherical domains with the average sizes of 50-100 nm. Some of these small domains further aggregated to form large hydrophilic regions. The proton conductivity values were measured in the range of 10⁻² S/cm in water and increased with increasing IEC and temperature.     

Poly(ether ether ketone)‐bischromenes: Synthesis,characterization, and influence on thermal,mechanical, and thermo mechanical properties of epoxy resin

Poly(ether ether ketone) s with terminal propargyl groups (PEEK‐PR) were synthesized from hydroxyl terminated PEEK (PEEKTOH) and characterized. The heat‐triggered polymerization of PEEK‐PR to poly bischromenes having PEEK backbone was confirmed by Fourier transform infrared spectroscopy and differential scanning calorimetric studies. PEEK‐PR was blended with a bisphenol based epoxy resin‐diamino diphenylsulphone system in different proportions and cured to form PEEK‐bischromene‐interpenetrated‐epoxy‐amine networks. Tensile strength and elongation of the cured blends increased up to 10‐phr loading of PEEK‐PR and then declined. Tensile moduli of all formulations were comparable. Fracture toughness increased by a maximum of 33%, and the fractured surface morphology showed a ductile fracture. The blends exhibited slightly lower glass transition temperature to that of the neat epoxy‐amine system. A reference sample of epoxy‐amine was processed with the optimum loading of the precursor polymer, PEEKTOH, and compared its properties with the PEEK‐PR incorporated epoxy systems. In this way, it is found that the incorporation of addition curable propargylated PEEK increases the strength characteristics with adequate thermal stability and fracture toughness for high‐performance structural applications.