Aromatic Polyketones Research Articles

Macrocyclic oligomers of the aromatic polyetherketone “PK99”: synthesis, fractionation, structural characterisation and ring-opening polymerisation

Cyclo-condensation of 4,4′-dihydroxybiphenyl with 1,3-bis(4-fluorobenzoyl)benzene under conditions of pseudo-high dilution affords a new series of macrocyclic ether-ketone oligomers. A number of these (the cyclic [2 + 2] dimer, [3 + 3] trimer, and [5 + 5] pentamer) have been isolated chromatographically as pure compounds. The odd-numbered macrocycles are readily-soluble, non-crystalline glasses, but the cyclic dimer is crystalline, high-melting (403 °C) and relatively insoluble. Its structure, determined by single-crystal X-ray methods, provides a new model for chain-folding within lamellar crystallites of aromatic polyketones. The [4 + 4] cyclic tetramer, although detectable by MALDI-TOF MS, appears to be so insoluble that it cannot be extracted from the product mixture. The amorphous cyclic trimer undergoes ring-opening polymerisation at 300 °C in the presence of a fluoride initiator, to give tough, semi-crystalline polymer.

Polymorphic Transitions in Oligo(aryl ether ketone)s Studied by Real Time X-ray Scattering

The crystal phase transitions occurring in oligo(aryl ether ketone) samples were studied, in real time, by means of X-ray scattering using synchrotron radiation. One sample is a typical molecular compound with 7 aryl units (m7) while the other two samples, containing 11 aryl units (p11 and m11), exhibit the presence of a polymeric component. In relation to the polymorphic transition previously reported for aromatic polyketones, the phase transition study of the sample p11 clarifies the role of chain length in the thermal behavior of aromatic polyketones. The structural variations, due to crystal phase transitions, as revealed by X-ray diffraction during heating of the samples are not accompanied by the parallel changes in the DSC thermograms. The two endothermic peaks observed for the samples p11 and m11 are associated with the melting of crystals with short and polymeric chains. Although the amount of polymer component reaches about 75% in the case of p11 (30% for m11), it does not exhibit the double melting phenomenon commonly observed for aromatic polyketones. A structural mechanism is suggested to explain the absence of such a phenomenon for the p11 and m11 samples.

A Polyketone Synthesis Involving Nucleophilic Substitution via Carbanions Derived from Bis(α-aminonitrile)s. 4. Aromatic Poly(ether ketone)s

To address the insolubility problem of polyketones, we used an approach to high molecular weight wholly aromatic polyketones without ether linkages via soluble precursors derived from isophthaldehyde-based bis(aminonitrile)s. Polymerization of bis(α-aminonitrile)s with activated dihalides using NaH as base in DMF yielded soluble, high molecular weight poly(aminonitrile)s, which were hydrolyzed in acidic conditions to produce the corresponding aromatic polyketones without ether linkages or alkyl substituents in the polymeric backbones. These polyketones displayed excellent thermal properties and solvent resistance. For the synthesis of poly(aminonitrile)s and polyketones containing ether linkages in the polymeric backbone, only low to medium molecular weight polymers were obtained. Model studies proved that the carbanions of the aminonitriles reacted with ether linkages to form more stable phenoxide anions and cause the termination of the polymerization.

Reduction of carbonyl groups in aromatic polyketones: synthesis and characterization of methylene-bridged polyaryl-ethers and -thioethers

The carbonyl groups in eight high-performance polyaryl-etherketones and -thioetherketones were reduced to methylene linkages in high yield by treatment at room temperature with triethylsilane in a mixture of trifluoroacetic acid or methanesulphonic acid with either dichloromethane or chloroform. When the starting polyketone is readily-crystallizable, the reduced polymer also tends to crystallize during workup. Amorphous polyketones likewise give amorphous reduction products. The methylene-bridged polymers in general have significantly lower melting points and/or glass transition temperatures than their parent polyketones.

Crystallization Kinetics and Polymorphism in Aromatic Polyketones (PEKEKK) with Different Molecular Weight

Simultaneous wide and small X-ray scattering (WAXS and SAXS) real time experiments using synchrotron radiation were performed to investigate poly-aryl(ether ketone ether ketone ketone) (PEKEKK) samples with different molecular weights obtained by precipitation polycondensation. Isothermal melt crystallization experiments, using two crystallization temperatures, Tc (differing by 10 °C) for each polymer grade were carried out. The phase transition temperature from polymorphic form II to form I was investigated in the samples as obtained. The variation of the index of crystallinity during heating was shown to depend on molecular weight. The index of crystallinity and X-ray long period values of the isothermal melt-crystallized samples observed at Tc and then at room temperature depend on the Tc values. For the lowest viscosity sample the microstructure is also molecular weight dependent. Avrami analysis of the 110(I) reflection leads to the conclusion that a similar crystallization mechanism takes place for the samples investigated.

The structure and morphology of lamellar single crystals of PK99, with a note on melt growth rates

Lamellar single crystals of the aromatic polyketone PK99 have been grown from dilute solution in benzophenone. The crystals are multilayer and shaped like extended leaves, they twist about their long axes. Selected area electron diffraction and wide angle X-ray diffraction (WAXD) of crystal mats show that the unit cell is orthorhombic with a = 0.788 nm, b = 0.609 nm and c = 4.82 nm. This structure is also found for the melt drawn fibre and is similar to that suggested by other authors who looked at melt crystallized materials. The unit cell is slightly larger than the unit cells of PEEK and PEK in the h k 0 plane. Small angle X-ray diffraction of solution grown crystals inidcates a long period of 7.86 nm, this thickness is close to one and a half times the chain repeat. The growth rate from the melt has been investigated as a function of the two techniques agree within the experimental errors. As has been found by other authors, there is a maximum growth rate at 260°C, a minimum between 235 and 240°C and a second, much lower, maximum at 230°C.

Polyketone Synthesis Involving Nucleophilic Substitution via Carbanions Derived from Bis(α-amino nitrile)s. 2. Wholly Aromatic Polyketones without Ether Linkages

To address the insolubility problem of polyketones, we used a new approach to high molecular weight wholly aromatic polyketones without ether linkages via soluble precursors derived from isophthaldehyde-based amino nitriles.1 High molecular weight, soluble poly(amino nitrile)s 2 were synthesized from the anions of these bis(amino nitrile)s 1 and 4,4‘-difluorobenzophenone using sodium hydride as base under mild reaction conditions. Hydrolysis of the poly(amino nitrile)s under acidic conditions yielded the corresponding polyketone, poly(p-phenylenecarbonyl-p-phenylenecarbonyl-m-phenylenecarbonyl) (3). This all aromatic polyketone, with an absence of ether linkages in the polymer backbone, displays excellent thermal properties and solvent resistivity. It is infusible and insoluble in most common organic solvents.

Aromatic polymers obtained by precipitation polycondensation. 6. Morphology of polyketone particles

AbstractSyntheses of aromatic polyketones in the form of particles were performed using a very small monomer concentration (0.05 mol/1) by the precipitation polycondensation method. Some of these particles present highly ordered elongated needle‐like structures (whiskers) particularly for the all‐para polyketone samples. The use of isophthaloyl instead of terephthaloyl for the same low monomer concentration produces, in addition to the globular particles, bundles of ribbon‐like structures. The average size of the needle‐like particles is 1−5 μm in width and 150−250 μm in length. The factors controlling the morphology texture and size of the whiskers and ribbons are shown to be the polymer structure and the reaction conditions. Formation mechanisms are discussed.

Synthesis of aromatic polyketones by using biphenylene monomers

Bisfunctional biphenylene monomers were designed, synthesized, and inspected as building blocks for aromatic polyketone synthesis. Starting from 2,2′-dimethoxybiphenylene ( 1), a highly activated acyl-acceptant biphenylene monomer affording high molecular weight polyketones, two types of biphenylene monomers were developed: 5,5′-bis(3[4]-chlorobenzoyl)-2,2′-dimethoxybiphenylenes ( 6) which readily gave the corresponding polyketones by nickel-catalyzed aromatic coupling polymerization and 2,2′-bis(trifluoromethyl)-4,4′-biphenylenedicarboxylic acid ( 27) which reacted with biphenylene 1 in P 2O 5CH 3SO 3H to give the corresponding fluorinated aromatic polyketone, selectively. The related model reactions for both monomer synthesis and polymerization were also investigated.

Aromatic Polymers Obtained by Precipitation Polycondensation. 3. Thermal Behavior and Microstructure of PEKEKK Particles

In the second part of this series the influence of monomer concentration on the chemical structure and the shape and size of poly(aryl ether ketone ether ketone ketone) (PEKEKK) particles was reported. The present study of the thermal behavior and microstructure of aromatic polyketone samples in the form of particles has been carried out by means of differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). Samples before and after reprecipitation and annealing were investigated. Similar to other polyketones, PEKEKK shows two polymorphic forms: form II, less stable, is currently observed in the samples, while the reprecipitated polymer preferentially shows form I. Form II is partially converted into form I upon short annealing treatment of the material. The semicrystalline materials show melting points and glass transition temperatures which are higher for the samples with higher molecular weight and more regular chain structure. A comparison of thermal properties of “as obtained” and “reprecipitated” samples reveals the influence of the particle architecture on the chain mobility. The latter determines the ability of polyketone chains to crystallize. Infrared dichroism was also used to characterize the arrangement of polymer chains inside the polyketone particles showing crystal habits.

芳香族ポリケトンの合成に関する最近の展開

Aromatic polyketone is one of the most highly performed super engineering plastics With the progress of clarification of the exact feature of structure and thermal behavior of the polymers, a lot of novel aromatic polyketones have appeared and various synthetic approaches were undertaken in these years The recent advances of polyketones are reviewed from synthetic interests. (1) New synthetic reactions, introduction and removal of tentative auxiliary groups in order to maintain the flexibility of polymer chain during chain elongation reaction, and uses of transition metals as a highly effective catalyst were developed for achievement of high-molecular-weight polymer skeleton. (2) Fundamental structural perturbation was undertaken by introduction of crankshaft rings and additional conjugated moieties. (3) Introduction of side groups and their chemical transformation were undertaken to perform new structures and advanced properties. (4) Fine syntheses and reactions of designed oligomers and polymer precursors both for model studies and reactive oligo/polyketones were also investigated. The reports in 1992 and later were mainly surveyed.

Aromatic homopolymers obtained by precipitation polycondensation: 1. Synthesis of naphthalene-containing polyketones

High molecular weight film-forming semicrystalline aromatic polyketones with a regular structure were obtained by precipitation electrophilic Friedel-Crafts polycondensation of 2,6-naphthalenedicarboxylic acid chloride with diphenyl ether, 1,4-bis( p-phenoxy) benzophenone and 1,4-bis( p-phenoxybenzoyl) benzene. Using 1H and 13C n.m.r. spectroscopy, the polyketones obtained were shown to be linear with para-substituted arylene fragments in the main chain. These polymers are soluble in strong protic acids and in common organic solvents, such as dichloroacetic acid and CHCl 3/CF 3CO 2H mixtures. Depending on the chemical structure, these ‘as-made’ polyketones were found to show multiple melting behaviour on heating.

Synthesis of Aromatic Polyketones by Direct Polycondensation Between Terephthalic Acid and Diaryl Compounds

Abstract A convenient method for the synthesis of a new series of polyarylketones with relatively high molecular weights has been investigated. The polymers were prepared readily by direct polycondensation of terephthalic acid with a series of diaryl compounds using phosphorous pentoxide/trifluoromethanesulfonic acid (w/w = 1/10), phosphorous pentoxide/methanesulfonic acid (w/w = 1/10), and aluminum chloride/phosphorous oxychloride (w/v = 1/3) as condensing agents. Among the three, the phosphorous pentoxide/trifluoromethanesulfonic acid pair was found to be most efficient and was studied in detail. The thermal and crystalline properties of the resulting polyarylketones were characterized. All of the polyketones prepared in the present study are crystalline and their glass transition temperatures and melting points depend greatly on the structure of the diaryl compounds employed.

Synthesis of wholly aromatic polyketones using 2,2'-dimethoxybiphenyl as the acyl-acceptant monomer

Polyketones [Ph(OMe)-Ph(OMe)-COArCO] n (Ar= Ph, PhOPh, C 10 H 6 ) are synthesized by solution polycondensamtion. The polymers are fully amorphous, with T g 's in the 200-217°C range and intrinsic viscosities in the 0.10-0.71 dL/g range (0.3g/dL in 96% H 2 SO 4 )

A new polymerization reaction for the synthesis of aromatic polyketones

A new polymerization reaction for aromatic polyketones is described based on palladium-catalyzed cross-coupling of aromatic diacid chlorides and bis(trimethylstannane) monomers. This method addresses some of the shortcomings of current synthetic approaches to this valuable class of thermoplastics. Most importantly, the polymerization can be carried out under mild conditions and polymer backbones free of ether linkages can be realized. Several high molecular weight, soluble polyketones having good thermal stability are synthesized using this polymerization reaction. An improved synthesis of aromatic bis-(trimethylstannane) monomers is also described that provides monomers in high yield

Polyphthalazines and polyisoquinolines with rigid-rod-like structures

The synthesis of new classes of N-heterocyclic polymers, the polyisoquinolines and polyphthalazines are described from intramolecular ring closure reactions of a novel aromatic polyketone. The polyketone was synthesized by the nickel-catalyzed coupling reaction of 1,2-bis(4-chlorobenzoyl)-3,6-diphenylbenzene. The thermal and mechanical properties of the N-heterocyclics synthesized from the polyketone are compared to analogous N-heterocyclics containing flexible linkages synthesized from poly(ether ketone)s containing ortho-dibenzoylbenzene moieties.

The crystal lamellar morphology of an aromatic polyketone with unusual crystallization and melting behaviour

Wide-angle and small-angle X-ray scattering and differential scanning calorimetry are used to elucidate the lamellar morphology of an aromatic polyketone (designated PK99). PK99 has three unusual crystallization and melting characteristics. First, there is a coupled melting and recrystallization process at around 260°C, well below the final melting point of 306°C; this process suggests two crystal forms. Secondly, there are two maxima in the growth rate versus temperature characteristics. Thirdly, the melting point is relatively low compared with the T g (158°C). WAXS shows that above and below the 260°C process there is no essential difference in the crystal packing. However, WAXS and SAXS data do show small step differences in crystal perfection and in lamellar thickness. The lamellar thicknesses are comparable to the periodic repeat length. This produces a new situation not normally observed in other crystalline polymers, where more than one type of lamellae can be formed containing different chain sequences. The unusual characteristics can be explained in terms of these different types of lamellae.

Crosslinkable aromatic polyketones with maleimide pendent groups

AbstractA novel class of crosslinkable aromatic polyketones with maleimide pendent groups were synthesized by Friedel–Crafts polymerization from 5‐maleimido‐isophthaloylchloride and various aromatic reagents. The synthesized polyketones showed a poor solubility. They were characterized by inherent viscosity measurements and infrared (IR) spectroscopy. Differential thermal analysis (DTA) revealed that their crosslinking occurred at relatiively lower temperatures (167–253°C) than did thermal polymerization of ordinary bismaleimides. The thermal‐and thermooxidative stability of crosslinked resins were evaluated by dynamic thermogravimetric analysis (TGA) as well as by isothermal gravimetric analysis (IGA). They were stable in N2 up to 303–329°C and formed anaerobic char yield 50–62% at 800–C. The thermal stability of crosslinkable polyketones was significantly increased after curing.

Synthesis and properties of polyketones containing thiophene links

AbstractA series of polyketones containing thiophene links was synthesized by the Friedel‐Crafts polymerization of these dithienylalkanes with aromatic diacid chlorides or dicarbonyl chlorides comprising thiophene links with diphenyl compounds. The resulting polymers had inherent viscosities in the range of 0.11–0.27 dL/g and showed poor solubilities to common organic solvents except strong acids. These thiophene‐based polyketones exhibited fairly good thermal stabilities. The TGA data revealed 5% weight losses at 375–450°C and residual weights at 500°C were 43–79% under nitorgen. It was found that the thermal stabilities of these polymers were superior to those of polymides or polysulfonamides containing thiophene links and almost comparable to common aromatic polyketones

Chemical structure and mechanical properties of a number of aromatic polyketones

Limiting strength and relaxation properties and heat stability were studied of a number of aromatic polyketones with various chemical structures. It was found that these polymers can be easily shaped into monolithic products with enhanced impact strength and good bending strength. The effect of chemical structure on thermal stability was investigated, as characterized by relaxation mechanical measurements in a broad strain and temperature range.