Physical aging of epoxy resin blended with poly(ether sulfone): Effect of poly(ether sulfone) molecular weight

The physical aging process of 4-4′-diaminodiphenylsulfone (DDS) cured diglycidyl ether bisphenol-A (DGEBA) blended with various molecular weights of poly(ether sulfone) (PES; M_n = 28,600, 10,600, and 6,137) was studied by DSC. For DGEBA/DDS system blended with a low MW PES-3 (M_n = 6,137), no phase separation of the polymer blend and only one enthalpic relaxation process due to physical aging was observed. Since the high MW PES-1 (M_n = 28,600) had a T_g close to that of fully cured DGEBA/DDS, the fully cured DGEBA/DDS/PES-1 blend had a broader glass transition than a neat DGEBA/DDS system. However, the DSC results showed two enthalpic relaxation processes due to the physical aging of PES-rich and cured epoxy-rich phases as the material was aged at 155 °C (30 °C below T_g). Since the T_gs of PES-1-rich and epoxy-rich phases overlapped with each other, the enthalpic relaxation processes corresponding to each phase coupled to each other in the earlier stage of physical aging. The medium MW PES-2 (M_n = 10,600) has a much lower T_g than that of fully cured DGEBA/DDS, two well separated T_gs were observed for the cured DGEBA/DDS/PES-2 blend, indicating the cured epoxy was immiscible with PES. Aging the polymer blend at 155 °C (24 °C below T_g1 of the PES-2-rich phase and 53 °C below T_g2 of the epoxy-rich phase) produced two well separated relaxation processes due to PES-2-rich and epoxy-rich phases. The experimental results suggested that aging the polymer blend at a suitable temperature would improve the phase separation between PES-1-rich and epoxy-rich phases.     

Synthesis and characterization of poly(ether sulfone) and poly(ether sulfone ketone) copolymers

Poly(ether sulfone) and poly(ether sulfone ketone) copolymers (I–V) were synthesized by the nucleophilic substitution reaction of 4,4′-dihydroxy diphenyl sulfone (DHDPS, A) with various mole proportions 4,4′-difluoro benzophenone (DFBP, B) and 4,4′-difluoro diphenyl sulfone (DFDPS, C) using sulfolane as solvent in the presence of anhydrous K₂CO₃. The polymers were characterized by physicochemical and spectroscopic techniques. All polymers were found to be amorphous, and the glass transition temperature (T_g) was found to increase with the sulfonyl content of the polymers. ¹³C-nuclear magnetic resonance (NMR) spectral data was interpreted in terms of the compositional triads, BAB, BAC, CAC, ABA, and ABB, and indicate that transetherification occurs at high concentration of DFBP units in the polymer (IV). The good agreement between the observed and calculated feed ratios validates the triad analysis. Thermal decomposition studies reveal that the thermal stability of the polymers increases with increase in the carbonyl content in the polymer. Activation energies for thermal decomposition were found to be in the range of 160–203 kJ mol⁻¹ with the cleavage of ϕ SO₂ bond being the preponderant mode of decomposition and depended on the block length of the sulfonyl unit. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2113–2121, 1999     

Miscibility and phase behavior in blends of phenolphthalein poly(ether sulfone) and poly(hydroxyether of bisphenol A)

Miscibility and phase behavior in the blends of phenolphthalein poly(ether sulfone) (PES-C) with poly(hydroxyether of bisphenol A) (PH) were investigated by means of differential scanning calorimetry (DSC), high resolution solid state nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR). It was found that the homogeneity of the as-prepared blends depended on the solvents used; N,N-dimethylformamide (DMF) provided the segmental mixing for PH and PES-C, which is confirmed by the behavior of single, composition-dependent glass transition temperatures (T_g's). To examine the homogeneity of the blends at the molecular level, the proton spin-lattice relaxation times in the rotating frame T_1ρ(H) were measured via ¹³C CP/MAS NMR spectroscopy as a function of blend composition. In view of the T_1ρ(H) values, it is concluded that the PH and PES-C chains are intimately mixed on the scale of 20-30 Å. FTIR studies indicate that there were the intermolecular specific interactions in this blends, involved with the hydrogen-bonding between the hydroxyls of PH and the carbonyls of PES-C, and the strength of the intermolecular hydrogen bonding is weaker than that of PH self-association. At higher temperature, the PH/PES-C blends underwent phase separation. By means of thermal analysis, the phase boundaries of the blends were determined, and the system displayed the lower critical solution temperature behavior. Thermogravity analysis (TGA) showed that the blends exhibited the improved thermal stability, which increases with increasing PES-C content.     

Synthesis and characterization of hexafluoroisopropylidene bisphenol poly(arylene ether sulfone) and polydimethylsiloxane segmented block copolymers

A series of hexafluoroisopropylidene bisphenol poly(arylene ether sulfone) (BAF PAES) segmented block copolymers with varying fractions of polydimethylsiloxane (PDMS) were synthesized by a condensation reaction of hydroxyl-terminated BAF PAES and dimethylamino endcapped PDMS. The segmented block copolymers have high thermal stability. The BAF PAES homopolymer exhibits a tensile modulus of 1700 MPa and an elongation at break of 16%. Copolymerizing BAF PAES with increasing molecular weight amounts of PDMS results in tensile properties ranging from plastic to elastomeric where the elongation is 417% for a segmented block copolymer with 64 wt% PDMS incorporated. The morphological properties of these segmented block copolymers were characterized by atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). AFM and TEM images show the segmented block copolymers were microphase separated, and comparison with bisphenol A (BA) PAES-b-PDMS segmented block copolymers revealed complex differences between the morphological behavior of the two systems. SAXS data of the segmented block copolymers supports AFM and TEM images, indicating microphase separation but little long-range order.     

Enhanced thermo-oxidative stability of sulfophenylated poly(ether sulfone)s

Monophenylated poly(ether sulfone)s (Ph-PES) and diphenylated poly(ether sulfone)s (DiPh-PES), were synthesized as starting materials for the preparation of sulfonated polymers with well-defined chemical structure. Mild post-polymerization sulfonation conditions led to sulfonated Ph-PES (Ph-SPES) bearing acid groups on both the pendant phenyl group and the backbone, and sulfonated DiPh-PES (DiPh-SPES) bearing acid groups only on the two pendant phenyl groups. Both series of polymers had excellent mechanical properties, high glass transition temperatures, good thermal and oxidative stability, as well as good dimensional stability. It is interesting to note that exclusively pendant-phenyl-sulfonated (bis-sulfophenylated) DiPh-SPES copolymers possessed obviously better thermal and oxidative stability compared with the corresponding pendant-phenyl-sulfonated/main-chain-sulfonated Ph-SPES copolymers. The methanol permeability values of the membranes were in the range of 7.0 × 10⁻⁷-9.4 × 10⁻⁸ cm²/s at 30 °C, which is several times lower than that of Nafion 117. DiPh-SPES-50 and Ph-SPES-40 also exhibited high proton conductivity (approximately 0.13 S/cm at 100 °C).     

聚醚砜/磺化聚醚醚酮共混膜的制备和性能

采用流延法制备了聚醚砜(PES)含量不同的PES/磺化聚醚醚酮(SPEEK)共混膜。PES与SPEEK具有良好的相容性。所制备PES/SPEEK共混膜的含水率、溶胀度和甲醇透过系数均随PES含量的增加而降低。虽然共混膜的质子传导性能有所降低.但阻醇性能和溶胀性能提高,这说明PES/SPEEK共混膜是一种很好的直接甲醇燃料电池用固体高分子电解质膜材料。     

Generation and characterization of carbon nano-fiber-poly(arylene ether sulfone) nanocomposite foams

In this study, carbon nano-fibers (CNFs) were used to increase the compressive properties of poly(arylene ether sulfone) (PAES) foams. The polymer composite pellets were produced by melt blending the PAES resin with CNFs in a single screw extruder. The pellets were saturated and foamed with water and CO₂ in a one-step batch process method. Dynamic mechanical thermal analysis (DMTA) was used to determine the reduced glass transition temperature (T_g) of the CNF-PAES as a result of plasticization with water and CO₂. Sharp transitions were observed as peaks in the tan δ leading to accurate quantitative values for the T_g. By accurately determining the reduced T_g, the foaming temperature could be chosen to control the foam morphology. Foams were produced which ranged in density from 290 to 1100 kg/m³. The foams had cell nucleation densities between 10⁹ and 10¹⁰ cells/cm³, two orders of magnitude higher than unreinforced PAES foam, suggesting that the CNFs acted as heterogeneous nucleating agents. The CNF-PAES foam exhibited improved compressive properties compared to unreinforced PAES foam produced from a similar method. Both the specific compressive modulus and strength increased by over 1.5 times that of unreinforced PAES foam. The specific compressive strength of 59 MPa for the CNF-PAES foam is similar to that of commonly used high performance structural foam, poly(methacrylimide foam).     

Synthesis of sulfonated poly(phthalazinone ether sulfone)s by direct polymerization

Sulfonated poly(phthalazinone ether sulfone)s with high molecular weight were directly prepared by polycondensation of 4-(4-hydroxyphenyl) phthalazinone with various ratios of disodium 5.5′-sulfonylbis(2-fluoro-benzenesulfonate) to 4-fluorophenyl sulfone. The resulting ionomers with high IEC showed low swelling. The low swelling originates from intermolecular hydrogen bonds, which is confirmed by variable temperature IR spectroscopy. The membranes show very good perspectives in PEMFC applications.     

聚醚砜的静电纺丝研究

采用聚醚砜(PES)的良溶剂二甲基甲酰胺(DMF)和非良溶剂丙酮(AC)为共溶剂体系,研究了溶剂组成、纺丝成形条件对静电纺丝PES纤维的形貌及纤维直径的影响。结果表明:DMF/AC的配比对于静电纺丝PES纤维形貌具有直接的调控作用,随着DMF/AC混合溶剂中AC用量的增加,纤维平均直径变大,纤维毡中串珠数目明显减少,纤维均一性变好;随着纺丝液浓度的升高,纺丝电压的增大,纤维的平均直径变大;接收距离的变化对纤维平均直径影响不大;PES最佳纺丝工艺条件为纺丝溶液质量分数13%,纺丝电压15 kV,接收距离10 cm,mDMF/mAC为8.5/1.5,在此条件下,可以获得纤维平均直径为96 nm的PES纤维毡。     

Poly(arylene ether sulfone) multi-block copolymers bearing perfluoroalkylsulfonic acid groups

Poly(arylene ether sulfone) (PAES) multi-block copolymers bearing perfluoroalkylsulfonic acid moieties were prepared from hydrophilic and hydrophobic prepolymers. The latter were synthesized by reaction of N,N-diisopropylethylammonium 2,2-bis(p-hydroxyphenyl)pentafluoropropanesulfonate (HPPS) with bis-(4-fluorophenyl) sulfone (FPS), and biphenol (BP) with FPS, respectively. Prepolymers and multi-block copolymers were prepared at 180 °C in N,N-dimethylacetamide in the presence of K₂CO₃. The prepolymers were reacted overnight; the multi-block copolymers were reacted only 80 min to minimize transetherification. Prepolymers and multi-block copolymers were characterized using ¹H and ¹³C NMR. ¹⁹F NMR provided molecular weight of hydrophilic prepolymers bearing aryl fluoride end groups. GPC was used to characterize the multi-block copolymers. Copolymer block lengths were determined by quantifying ¹³C NMR peak areas of quaternary carbon atoms adjacent to sulfur in FPS moieties. Hydrophilic and hydrophobic block lengths were in the range 9.4-23.4 and 4.4-11.8 repeating units, respectively. AFM showed phase separation for all block lengths. Conductivity at 80 °C and 100% relative humidity ranged from 6.2 to 34.3 mS/cm, with the best value obtained for hydrophilic/hydrophobic block lengths of 13.3/6.0.     

Structure-property-performance relationships of sulfonated poly(arylene ether sulfone)s as a polymer electrolyte for fuel cell applications

This article focuses on structure-property-performance relationships of directly copolymerized sulfonated polysulfone polymer electrolyte membranes. The chemical structure of the bisphenol-based disulfonated polysulfones was systematically alternated by introducing fluorine moieties or other polar functional groups such as benzonitrile or phenyl phosphine oxide in the copolymer backbone. Ac impedance measurements of the polymer electrolyte membranes indicated that fluorine incorporation increased proton conductivity, while polar functional group incorporation decreased conductivity. Likewise, other properties such as water uptake and ion exchange capacity are impacted by the incorporation of fluorine moiety or polar groups. These properties are critically tied with H₂/air and direct methanol fuel cell performance. We have rationalized fuel cell performance of these selected copolymers in light of structure-property relationships, which gives useful insight for the development and application of next generation polymer electrolytes.     

Synthesis and characterization of poly(arylene ether sulfone)-b-polybenzimidazole copolymers for high temperature low humidity proton exchange membrane fuel cells

Multiblock copolymers based on poly(arylene ether sulfone) and polybenzimidazole (PBI) with different block lengths were synthesized by coupling carboxyl functional aromatic poly(arylene ethers) with ortho diamino functional PBI oligomers in NMP, selectively doped with phosphoric acid, and evaluated as a high temperature proton exchange membrane (PEM). Transparent and ductile membranes were produced by solvent casting from DMAc. From dynamic mechanical analysis (DMA), the neat copolymer membranes showed two distinct glass transition temperatures which implies the existence of a nanostructured morphology in the membranes. These two nanophases became more distinct with increasing block length. The membranes were immersed in various concentrations of phosphoric acid solution to produce the proton conductivity. The doping level increased with increasing concentration of the acid solution and a maximum doping level of 12 was achieved when 14.6 M phosphoric acid solution was used. The acid doped membranes showed significantly reduced swelling behavior compared to a control conventional phosphoric acid doped PBI homopolymer system which appears to be related to the selective sorption into the PBI phase. The ionic conductivity of the doped samples at 200 °C afforded up to 47 mS/cm without external humidification. The protonic conductivity was found to increase with block length at a given doping level, reflecting the sharpness of the nanophase separation and the effect was even more prominent at a low doping level of 6-7. It is suggested that the phosphoric acid doped multiblock copolymer system would be a strong candidate for high temperature and low relative humidity PEM applications such as those required for stationary power.     

The study on poly(ether sulfone) modified cyanate ester resin and epoxy resin cocuring blends

Poly(ether sulfone) terminated with phenolic hydroxyl groups modified cyanate ester resin and epoxy resin cocuring blends were investigated by differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, rheometry, and mechanical properties measurement. The results suggested that poly (ether sulfone) (PES) could accelerate the polycyclotrimerization reaction of cyanate ester and cocuring processes between cyanate ester and epoxy of modified blends because of the presence of phenolic hydroxyl groups at the end of the PES molecules. It was found that the evolution of the morphologies and complex viscosities of the modified blends sensitive to molecular weight and content of PES, the tensile strength and elongation at break of the modified blends were correlated with the morphologies of modified blends. Moreover, the evolution of complex viscosities of the modified blends also showed an exponential growth at the early stage of phase separation, which demonstrated experimentally that the coarsening processes of droplets of bisphenol‐A dicyanate and diglycidyl ether of bisphenol A and the final morphologies obtained in the blends modified with PES were affected by viscoelastic behavior. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

聚醚砜纤维及织物性能研究

将聚醚砜(PES)进行熔融纺丝,制得PES纤维,并织成布样,对纤维及其织物的性能进行了研究。结果表明:PES纤维的力学性能不稳定,放置一定时间,其强度下降,需经140℃高温热定型加以改善。纤维回潮率为2．33%;织物极限氧指数为26．9%,紫外吸光度低于1．6,体积比电阻为8．13×10~(13)Ω·cm,摩擦静电压为7 272 V,1 min后衰减电压为5 519 V。     

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.     

Sulfonated poly(arylene ether sulfone) as an electrode binder for direct methanol fuel cell

Sulfonated poly(arylene ether sulfone) (sPAES) is synthesized and characterized for the application to the electrode binder for direct methanol fuel cell (DMFC). The effect of sPAES binder in the electrode on the cell performance is studied. The cell based on sPAES binder showed a good adhesion to the sPAES membrane, while Nafion binder is delaminated from the sPAES membrane after supplying the fuel for a prolonged time. The sPAES binder for electrode is found to be more efficient in achieving long-term stability of the cell performance than the conventional Nafion binder.     

Sulfonated poly(arylene ether sulfone) membranes based on biphenol for direct methanol fuel cells

A series of sulfonated poly(arylene ether sulfone) (PAES) were synthesized through direct aromatic nucleophilic substitution polycondensation of 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (SDCDPS), 4,4-dichlorodiphenylsulfone (DCDPS) and 4,4-biphenol (BP). With increasing sulfonate groups in the polymer, water uptake, ion exchange capacity (IEC) and proton conductivities increased, resulting from enhanced membrane hydrophilicity. The membranes exhibited higher thermal stability up to 300 °C, verified by thermogravimetric analysis (TGA). A maximum proton conductivity of 0.11 S/cm at 50 mol% of sulfonation degree was measured at 30 °C, which is slightly higher than Nafion®117 membrane (0.0908 S/cm). However, the methanol permeability of the PAES membrane was much lower than that of Nafion®117 membrane. As a result, a single cell performance test demonstrated that PAES-BP with 50 mol% sulfonation degree exhibited higher power density than Nafion®117.     

聚芳醚砜酮纤维的热性能

采用DSC、TG测定了含联苯结构聚芳醚砜酮 (PPESK)纤维的热性能 ,结果表明 ,纤维的玻璃化温度随砜酮比的增大而提高 ,纤维的起始分解温度大于 463℃。当砜酮比为 15 / 85 ,5 0 / 5 0 ,75 / 2 5时 ,纤维的玻璃化温度分别为 2 5 7.62 ,2 78.64 ,2 79.71℃ ;热分解活化能分别为 15 0 .8,2 19.9,195 .5kJ/mol;热分解反应级数分别为 1,1.76,1级     

Macrocycles 25. Cyclic poly(ether sulfone)s derived from 4-tert-butylcatechol

Poly(ether sulfone)s were prepared by polycondensation of silylated 4-tert-butylcatechol and 4,4′-difluorodiphenylsulfone in N-methylpyrrolidone. The feed ratio and the reaction time were varied to study the influence of stoichiometry and conversion on molecular weight and extent of cyclization. Molecular weights and molecular weight distributions (MWD)s were characterized by SEC measurements calibrated with polystyrene. Light scattering confirmed that calibration with polystyrene gives reasonable results and revealed a tendency towards a bimodal MWD for the samples rich in cycles. The MALDI-TOF mass spectrometry indicated that the extent of cyclization increased with higher conversion and with optimization of the stoichiometry. This interpretation was confirmed by ¹H NMR endgroup analyses. For the samples with the highest molar masses only mass peaks of cycles were found, which were detectable up to 20 000 Da before and up to 27 000 Da after fractionation. Via the pseudo-high dilution method low molar mass poly(ether sulfone) containing more than 95 mol% of cycles were prepared, and even these low molar mass samples had broad MWDs. DSC measurements indicated that the glass transition temperatures depend on the structure of the endgroups and increase with higher fractions of cycles.     

Fluorinated poly(arylene ether sulfone)s for polymeric optical waveguide devices

Pentafluorophenyl sulfone was prepared by oxidation of pentafluorophenyl sulfide. Ethynyl terminated fluorinated poly(arylene ether sulfone) (EFPAESO) was synthesized via nucleophilic aromatic substitution from 4,4′-(hexafluoroisopropylidene) diphenol or 4,4′-(trifluoromethylphenylisopropylidene) diphenol with an excess of pentafluorophenyl sulfone, followed by reaction with 3-ethylnylphenol. The molecular weights (M_ns) of the polymers determined by GPC with polystyrene standard were in the range of 6,400-17,200 and polydispersities (M_w/M_ns) were in the range of 2.25-3.19. This EFPAESO showed very high thermal stability up to 479 °C for 5% weight loss in TGA in air. T_g of the polymer was changed from 148 to 196 °C after curing. The cured films showed good chemical resistance and high thermal-stability. At 1550 nm wavelength, the refractive indices of the copolymer films were in the range of 1.5037-1.5504 and birefringences were in the range of 0.0021-0.0025. The optical loss for EFPAESO was less than 0.37 dB/cm at 1550 nm wavelength.