Ketone Linkages Research Articles

Melt-state degradation mechanism of poly (ether ketone ketone): the role of branching on crystallization and rheological behavior

In the melt-state, poly (ether ketone ketone) (PEKK) undergoes structural changes to the polymer backbone due to its high melting temperature. In this work, the thermal degradation mechanism of PEKK in the melt-state in air is identified using a combination of molecular dynamics (MD) simulations, X-ray photoelectron spectroscopy (XPS), and rheology. Ether linkages in the PEKK backbone are shown to have the lowest bond dissociation energies and preferentially undergo chain scission compared to ketone linkages. Upon chain scission, the formed radical species undergo hydrogen abstraction, chain transfer, and a coupling reaction, resulting in altered viscoelastic properties. Dynamic rheological behavior of PEKK thermally aged in the melt-state display viscoelastic characteristics of long-chain branched polymers. Results indicate that the PEKK rheological properties are highly dependent on time in the melt-state as well as angular frequency. Increased exposure times in the melt-state result in increased complex viscosity and a reduction in the degree and rate of crystallization. Thermal history has a significant impact on thermomechanical properties in the melt-state and during crystallization.

Synthesis of cardo poly(arylene ether ketone amide)s by heterogeneous palladium-catalyzed polycondensation of aromatic diiodides, aromatic diamines containing cardo groups and CO

New cardo poly(arylene ether ketone amide)s were synthesized by heterogeneous palladium-catalyzed carbonylative polycondensation of aromatic diiodides with ether–ketone linkages, aromatic diamines bearing cardo groups, and carbon monoxide. Polymerizations were conducted in N,N-dimethylacetamide (DMAc) at 120 °C in the presence of a bidentate phosphino-functionalized magnetic nanoparticles-immobilized palladium complex [Fe3O4@SiO2-2P-PdCl2] and 1,8-diazabicyclo[5,4,0]-7-undecene (DBU), yielding a series of cardo poly(arylene ether ketone amide)s with inherent viscosities up to 0.77 dL/g. All the polymers were readily soluble in various dipolar aprotic solvents at room temperature. These polymers showed good thermal stability with the glass transition temperature of 223–289 °C, the temperature at 5% weight loss of 441–464 °C in nitrogen. These cardo poly(arylene ether ketone amide)s could afford transparent, flexible, and strong films by solution-casting with good tensile properties. These polymer films exhibited lower dielectric constants, lower water uptakes, and higher optical transparency. Furthermore, this heterogeneous palladium catalyst can facilely be separated from the reaction mixture by simply applying an external magnet and recycled at least eight times with almost consistent activity.

Flexible Ketone-bridged organic porous nanospheres: Promoting porosity utilizing intramolecular hydrogen-bonding effects for effective gas separation

Two series of flexible ketone-bridged nanoporous organic polymers (NOPs) are readily prepared through one-pot Friedel-Crafts acylation polymerization using pyromellitic dianhydride (PMDA) and terephthaloyl chloride (TC) as acylation reagents, respectively. The carboxyl-appended samples (termed NOP-52@COOH and NOP-53@COOH), derived from PMDA, feature a stable spherical morphology. Unexpectedly, our NOP-52@COOH and NOP-53@COOH deliver much higher surface areas (eg. 738 m2 g−1 for NOP-52@COOH) and pore volumes (eg. 0.53 cm3 g−1 for NOP-52@COOH) than the carboxyl-free samples (i.e. NOP-52 and NOP-53). This is significantly different from the reported trend that the introduction of appended group always leads to inferior surface area and pore volume. The enhancement in porosity originates from the hydrogen-bonding effect between carboxyl and the ketone linkage that effectively prevents the networks from collapsing. More importantly, the as-made carboxyl group-containing networks exhibit stronger affinity towards guest CO2 molecules after comparing to those carboxyl-free ones, and have a competitive CO2 capture capacity under ambient conditions (159 mg g−1, 273 K/1 bar). This provides a feasible pathway for both developing high-surface-area organic polymers with flexible linkages and engineering pore surface properties.

Facile Approach to Preparing Microporous Organic Polymers through Benzoin Condensation

A series of microporous organic networks linked by α-hydroxyl ketone were synthesized based on benzoin self-condensation of multiformyl-containing building blocks. Fourier transform infrared and solid-state (13)C CP/MAS NMR spectroscopy were utilized to confirm the α-hydroxyl ketone linkage of the obtained polymers. The hollow microspheric morphology can be observed from scanning electron microscopy and transmission electron microscopy images. The materials, with Brunauer-Emmet-Teller specific surface area up to 736 m(2) g(-1), possess a hydrogen storage capacity up to 1.42 wt % at 77 K and 1.0 bar and a carbon dioxide uptake up to 15.3 wt % at 273 K and 1.0 bar. These excellent characteristics would make them become promising candidates for gas storage.

Fluorinated/non-fluorinated sulfonated polynaphthalimides as proton exchange membranes

Two -SO3H containing diamine monomers, 2,5-bis(4-amino-2-trifluoromethylphenoxy)benzenesulfonic acid and 2,5-bis(4-aminophenoxy)benzenesulfonic acid were successfully synthesized through a typical aromatic nucleophilic substitution reaction followed by a reduction reaction, respectively. Derived from the diamine monomers, two series of sulfonated naphthalic polyimides (polynaphthalimides) containing ether and ketone linkages were synthesized through a “one pot” polymerization reaction. Some properties including thermal stability, mechanical properties, water uptake, swelling dimensional ratio, methanol permeability, and proton conductivity were thoroughly investigated. Some exhibited attractive properties as proton exchange membranes. It was found that the fluorinated series (CF3-SPI-X) exhibited higher dimensional stability and lower methanol permeability in comparison with non-fluorinated ones (SPI-X) at the same −SO3H group content. Open image in new window

Sulfonated naphthalenic polyimides containing ether and ketone linkages as polymer electrolyte membranes

Two series of sulfonated naphthalenic polyimides containing ether and ketone linkages (SPI-KK-X and SPI-K-X) were prepared by a one-pot polymerization reaction of sulfonated diamine monomers, 1,4-bis[3-sodium sulfonate-4-(4-aminophenoxy)benzoyl]benzene or 4,4-bis[3-sodium sulfonate-4-aminophenoxy]benzophenone, with 4,4-diaminodiphenyl ether and 1,4,5,8-naphthalenetetracarboxylic dianhydride. The membranes cast from the resulting polymers had good thermal and oxidative stability, dimensional stability and mechanical properties. At 80 °C, the proton conductivities of several samples, including SPI-KK-1, SPI-K-1 and SPI-K-2 were higher than 0.10 S/cm, which were comparable to that of Nafion. Methanol permeabilities of the obtained polymer electrolyte membranes (PEMs) were in the range of 1.43–2.03 × 10 −7 cm 2/s, which were several times lower than that of Nafion 117. It is interesting to note that the SPI-KK-X series, having a more rigid phenyl–ketone–phenyl–ketone–phenyl moiety, had a lower dimensional swelling ratio and lower methanol permeability in comparison with the corresponding SPI-K-X series at the same level of ion exchange capacity (IEC).

Effects of crosslinking ratio and aging time on properties of physical and chemical cellulose gels via 1-butyl-3-methylimidazolium chloride solvent

Papers used in the field of electro-responsive applications are known as Electroactive-papers (EAPaps), consisting primarily of a cellulose. 1-Butyl-3-methylimidazolium chloride is an interesting ionic liquid that acts as an effective cellulose solvent for EAPaps due to its high solubility without chain derivatization, less chain degradation, and stability in electro-responsive applications. In our work, physical and chemical cellulose gels were fabricated and studied for the effects of various crosslinking ratios (CR) and aging time (tag), with glutaraldehyde acting as the crosslinking agent. The crosslinking reaction conversion could be increased by increasing the CR and tag; the reaction products were ketone linkages and by-product water molecules. A difference in optical properties could be observed and related to the differing amounts of ketone linkages, as confirmed by FTIR-ATR quantitative analysis. UV–visible spectra showed that the prepared samples had a maximum wavelength λmax nm, a characteristic of ketone linkages. By-product water molecules exhibited plasticizing effects, as observed by the decrease in the storage moduli (G′) at 1 day aging time. The outward migration of by-product water molecules caused a slight increase in G′ at 15 days aging time due to a closer packing. The by-product water molecules induced the H+-hopping and more disordered domains resulting in an ease in ion migration. Our paper-gels showed potential characteristics towards electro-responsive applications: less preparation time (<14 h) and stable gel properties.

The Preparation and Characterization of Highly Fluorinated Poly(arylene alkylene ether)s

A series of highly fluorinated poly(arylene alkylene ether)s, P6CFXs (X = Non, S, K, SO, Ox) have been prepared by polycondensation reactions of 1H,1H,6H,6H,-perfluorohexane-1,6-diol (6CF-diol) with a series of decafluorodiphenyl compounds (DFPXs) including decafluorobiphenyl (DFP), decafluorodiphenyl sulfide (DFPS), decafluorobenzophenone (DFPK), decafluorodiphenyl sulfone (DFPSO), and decafluorodiphenyl oxadiazole (DFPOx). This aromatic nucleophilic substitution polycondensation can be effectively activated by cesium fluoride (CsF) and was completed in a few hours in N,N-dimethylacetamide (DMAc) at room temperature. High molecular weight polymers (Mn = 28 200−64 200 Da) have been prepared from DFP, DFPS, DFPSO, and DFPOx, while the reaction from DFPK only yields low-molecular weight materials (Mn < 8 000 Da). A model reaction using excess 6CF-diol (2.5 equiv of DFPK) reveals that the ketone linkage of the DFPK unit is cleaved by the attack of the activated hydroxyl group in the diol during the polycondensation. This cleavage is suppressed when potassium fluoride (KF) was used as a base, and a high molecular weight P6CFK (Mn = 33 200 Da) has been prepared. DSC analysis shows that all the resultant polymers are semicrystalline materials, and the melted samples display different crystallization rates in the order of P6CFNon > P6CFOx > P6CFK > P6CFSO ∼ P6CFS. This sequence is correlated with the bond angles of the X linkages, suggesting a significant influence of the bending of the X linkages on the crystallization capability of the polymers. The P6CFNon film has a hydrophobic surface with a water contact angle of 110°, while the other polymers showed reduced values with the increase of the polarities of the X linkages in the order of P6CFNon > P6CFS > P6CFK > P6CFOx > P6CFSO.

Synthesis of indaphyrins: meso-tetraarylsecochlorin-based porphyrinoids containing direct o-phenyl-to-beta-linkages.

The synthesis of indaphyrins, novel meso-tetraarylsecochlorin-derived chromophores incorporating o-phenyl-to-beta-linkages, is described. Oxidative diol cleavage of meso-tetraaryl-2,3-dihydroxy-2,3-chlorins results in the formation of a secochlorin bisaldehyde. Depending on the reaction conditions during the ring cleavage reaction, one or two of the aldehyde groups react with the adjacent o-phenyl positions, leading to an intramolecular electrophilic aromatic substitution of the o-phenyl proton, and the establishment of a direct o-phenyl-to-beta-linkage. The initially formed carbinol is spontaneously oxidized to the corresponding ketone. This modification forces the aryl groups into co-planarity with the macrocycle, allowing for interactions between the pi-electrons of the aryl groups, the ketone linkage, and those of the chromophore, resulting in a significant electronic modulation of the porphyrinic pi-system. The UV-vis spectroscopic properties of the free base, CuII, NiII, and ZnII indaphyrins are discussed.

Selective solid-phase extraction of polycyclic aromatic hydrocarbons by the chemically modified polymeric adsorbents with protoporphyrin IX

The chemically modified polymeric adsorbents were evaluated for selective solid-phase extraction of polycyclic aromatic hydrocarbons. Commercially available Amberlite XAD-2 and XAD-4 resins were modified with macrocyclic protoporphyrin IX or tetrakis(p-carboxyphenyl)-porphyrin through the ketone linkage. The variables that influence the selectivity and recovery of the solid-phase extraction were optimized. The best result was obtained with XAD-4 resins modified with macrocyclic protoporphyrin IX. After preconcentration and clean-up step, the polycyclic aromatic hydrocarbons were determined by gas chromatography with mass spectrometric detection. The method was used to determine polycyclic cromatic hydrocarbons in soil, and the recovery was in the range of 79.6% to 94.1%.

New Irreversible Adenosine A1 Antagonists Based on FSCPX

AbstractFor Abstract see ChemInform Abstract in Full Text.

Critical Role of Diffraction Simulation in Establishing the Crystal and Molecular Structures of Poly(biaryl ether ketone)s

Molecular modeling and diffraction simulation studies of the biphenyl-based poly(ether ketone)s [O−Ar−Ar−O−Ar−CO−Ar−Ar−CO−Ar−]n (3) and [−O−Ar−Ar−CO−Ar−]n (4, Ar = 1,4-phenylene), coupled with data obtained from an oligomer single-crystal study, have enabled their crystal and molecular structures to be determined from X-ray powder data. A crystallographically disordered structure in which the ether and ketone linkages are distributed randomly over the bridging positions of the polymer chain is potentially available to both polymers and undoubtedly occurs in their random 1:2 copolymer (5). The disordered structure is monoclinic (rather than orthorhombic as has previously been proposed), in space group P21/b, with two chains per unit cell. Rietveld refinement of this structure for polymers 3 and 4, based on X-ray powder data, gave final agreement factors (Rwp) of 5.7% and 6.6%, respectively. Analysis of X-ray fiber data by diffraction simulation methods suggests that the disordered structure always predomin...

New irreversible adenosine A 1 antagonists based on FSCPX

FSCPX ( 1) and its amide analogue ( 2) have been reported to exhibit potent and selective irreversible antagonism of the A 1 adenosine receptor (A 1AR) when used in in vitro biological preparations. In order to obtain an irreversible A 1AR antagonist with improved stability, analogues of FSCPX incorporating the chemoreactive 4-(fluorosulfonyl)phenyl moiety separated from the xanthine pharmacophore by a ketone linkage were explored. Compounds 4a– c exhibited improved affinity for the A 1AR and concentration-dependent irreversible binding to the A 1AR.

Crystallographic Equivalence of Ether and Ketone Groups in Poly(aryl ether ketone)s

Crystallographic equivalence of ether and ketone in all para-substituted PAEKs crystallized in Form I was discussed in this paper. In a word, crystallographic equivalence between ether and ketone groups is tenable when the polymer contains only phenyl rings in the repeat unit. If the polymer contains a diphenyl group in the repeat unit, two cases should be distinguished. In the case of PEDEKK and PEEKDK. crystallographic equivalence between ether and ketone linkages is untenable. However. in the case of PEDK and PEDEKDK, crystallographic equivalence between ether and ketone linkages is still tenable. Chemical structures of PEDK and PEDEKDK.

Evaluation on the adsorption capabilities of new chemically modified polymeric adsorbents with protoporphyrin IX

A chemically modified polymeric adsorbent was synthesized to evaluate the availability as an adsorbent for solid-phase extraction (SPE) of phenol and chlorophenols. Commercially available Amberlite XAD-2 and XAD-4 resins were modified with macrocyclic protoporphyrin IX (PPIX) through the ketone linkage. Adsorption isotherms were obtained by batch experiments and the data were fitted to the Freundlich equation to calculate the adsorption parameters. Breakthrough volumes were measured by column experiments. Physical properties such as surface area, average pore diameter and micropore volume of resins were measured to correlate with the adsorption characteristics. As a result, adsorption capacity was increased for the chemically modified resins and it can be concluded that the increase of π–π interaction due to the introduction of the porphyrin molecule is the major factor for the increase of the adsorption capacity.

Solid-Phase Extraction of Phenol and Chlorophenols in Water with a Chemically Modified Polymer-Supported Tetrakis(p-carboxyphenyl) Porphyrin (H2TCPP)

A chemically modified sorbent was evaluated as a preconcentration substrate in solid-phase extraction of phenol and chlorophenols. Tetrakis(p-carboxyphenyl) porphyrin (H2TCPP) was chemically bonded to porous polymeric XAD resins by ketone linkage. Breakthrough volumes, recovery values, and detection limits were determined. The synthesized sorbent showed higher recoveries in tap water than commercially available sorbents such as XAD-2 and XAD-4.

Crystal and Molecular Structure of Poly(thioether−ketone) from Single-Crystal Oligomer Data and Diffraction Modeling. 2. Polymer Crystallized from the Melt or from Solution

The aromatic poly(thioether−ketone) [ArSArCO]n (Ar = 1,4-phenylene), PTEK, is known to exist in at least two different crystalline forms, one produced by orientation of the amorphous polymer and the other by crystallization from the melt. In the present work, X-ray powder diffraction studies interfaced to molecular modeling and diffraction simulation techniques have been used to determine the crystal and molecular structure of melt- or solution-crystallized PTEK. In this phase, the thioether−ketone polymer chains adopt a packing arrangement very different from that of their ether−ketone analogues. For solution-crystallized polymer, the unit cell is body-centered monoclinic (two chains per cell), space group I2, a = 7.58, b = 6.09, c = 10.25 A, β = 93.7°, density = 1.49 g cm-3. The thermal parameters required for this model are however rather high, suggesting the possibility of a disordered structure (in space group I2/a,) whereby thioether and ketone linkages are distributed at random over the available s...

Hyperbranched Poly(ether ketone) with Carboxylic Acid Terminal Groups: Synthesis, Characterization, and Derivatization

A new procedure is described for the formation of a hyperbranched poly(ether ketone) with carboxylic acid terminal groups. This preparation was based on the one-step synthesis of an AB2-type monomer 5-phenoxyisophthalic acid using phosphorus pentoxide/methanesulfonic acid as the condensing agent and solvent. The electrophilic aromatic substitution reaction led to the formation of the aryl ketone linkage. With the help of model compounds, 1H NMR studies revealed that the degree of branching of the poly(ether ketone) was about 55%. The terminated carboxylic acid groups were readily functionalized, yielding hyperbranched polymers with a variety of different functional chain ends. The nature of the chain ends was shown to dramatically affect physical properties of the hyperbranched macromolecules. The ammonium derivative was soluble in water and behaved as a unimolecular micelle.

Synthesis and characterization of meta-linked polyamides containing sulfone, ether and ketone linkages

High molecular weight aromatic polyamides were obtained from 4,4′-bis[(3-carboxyphenoxy)( p-benzoyl)]phenyl sulfone, by direct polycondensation reaction in N-methyl-2-pyrrolidone with various aromatic diamines, using triphenyl phosphite and pyridine as condensing agents. The polymers were characterized by solution viscosities, elemental analysis, thermogravimetric analysis, differential scanning calorimetry and infrared analysis. The polymers, obtained in 92–95% yield, possessed inherent viscosities in the range 0.50–1.35 dl g −1, glass transition temperatures between 210 and 228°C, and 10% weight loss temperatures in nitrogen and air above 490 and 460°C respectively. The effect of the different structures on properties such as solubility, molecular weight, T g and thermal behaviour were also studied.

The preparation by a solid-solid interaction route of aromatic polyamide materials containing sulphone, ether and ketone linkages

The polycondensation reactions between 4,4′-[sulphonyl bis(p-benzoyl)(p-phenyleneoxy)]dibenzoic acid (I) andp-phenylenediamine (II), 1,5-diaminonaphthalene (III), 4,4′-sulphonyldianiline (IV), 4,4′-diaminodiphenylsulphide (V) 4,4′-methylenedianiline (VI) and 4,4′-oxydianiline (VII) to form aromatic polyamides containing sulphone, ether and ketone linkages were attempted by a solid-solid interaction route. A stoichiometric 1∶1 molar ratio of solid reactants was dynamically heated directly in a TG/DSC apparatus, and simultaneous TG/FT-IR was performed to interpret the mechanism of reaction. The results suggest that the polycondensation is dependent on the diamine used. The formation of polyamide was successful when I interacted with II, III, VI and VII. The interaction with IV and V was in part successful because partial decarboxylation of the diacid, made unstable by the diamine, occurred before the condensation reaction.