M. G. Zolotukhin

Aromatic polymers obtained by precipitation polycondensation: 4. Synthesis of poly(ether ketone ketone)s☆

Abstract High molecular weight aromatic poly(ether ketone ketone)s were synthesized by the Friedel-Crafts polyacylation condensation of iso- and terephthaloyl chlorides with diphenyl ether, 1,4- and 1,3-bis(4-phenoxybenzoyl)benzenes. Depending on the monomers used for polycondensation, polyketones of regular structure with different iso-/tereisomer repeating unit ratio ( 100 0 , 50 50 , 0 100 ) in the main chain were obtained. Polymers of each repeating isomer unit were prepared in two different ways. All the polymer syntheses were performed as precipitation polycondensations and the resulting polymers were obtained in particle form. The influence of reaction conditions and preparation route on the polymer properties were examined. The monomer concentration and monomer stoichiometric ratio were found to affect the polymer viscosity. The size and shape of the polyketone particles obtained were also found to be governed by reaction conditions and preparation route.

Aromatic polymers obtained by precipitation polycondensation: 5. 1H and 13C n.m.r. study of poly(ether ketone ketone)s

Abstract High molecular weight, linear aromatic poly(ether ketone ketone)s with different iso-/tere-isomer repeating unit ratio ( 100 0 , 50 50 , 0 100 ) have been studied by 1 H and 13 C n.m.r. spectroscopy. The polymers were obtained in particle form by precipitation electrophilic Friedel-Crafts acylation condensation of iso- and terephthaloyl chlorides with diphenyl ether, 1,4- and 1,3-bis(4-phenoxybenzoyl)benzenes. Conventional 1 H and 13 C n.m.r. spectroscopy shows para -substitution in the diphenyl ether fragments of the main chain. Analysis of the expanded 1 H n.m.r. spectra for the ring proton resonances reveals defect meta - and ortho -structures. The amount and isomer ratio of these defect structures depend on the polymer structure and preparation path. The low field of 1 H n.m.r. spectra of polyketones based on ‘small monomers’ (diphenyl ether and iso- and terephthaloyl chlorides) were found to show additional minor signals corresponding to a different type of defect structure. A possible mechanism of formation of these defect structures is discussed.

ON THE EFFECT OF REACTION CONDITIONS ON MORPHOLOGY OF AROMATIC POLY(ETHER-KETONE)S, PEKK*

Aromatic poly(ether ketone ketone)s (PEKKs) of regular structure, containing 1,3- and 1,4-substituted phthalic acid units in a 1-to-1 ratio, were prepared by two methods: electrophilic and nucleophilic aromatic substitutions. Electrophilic preparations were performed as low-temperature precipitation polycondensations, and resulting polymers were obtained in the form of particles. Nucleophilic syntheses were carried out in N-cyclohexyl-pyrrolidone and diphenyl sulfone at 260°C and 290°C, respectively, in the presence of sodium and potassium carbonates. Differential scanning calorimetry (DSC) curves of the polyketones “as obtained” and “reprecipitated” revealed differences in their thermal behavior depending on the polymerization method, the synthetic route, and the reaction conditions used. The ability of samples to undergo molecular reorganization during heating, affected by polymerization conditions, is responsible for the diversity of DSC curves observed. A parallel X-ray study of the samples revealed small differences between diffractograms from the as-obtained materials, while they were similar for the reprecipitated ones. However, X-ray diffractograms of thermally treated samples showed further differences between the emerging crystalline structures that should be related to a different chain organization produced during the polymerization process. *Dedicated to Prof. Francisco J. Baltá Calleja on the occasion of his 65th birthday.

Relaxation behavior in model compounds of poly(aryl-ether-ketone-ketone) as revealed by dielectric spectroscopy

The relaxation behavior of a series of ether-ketone oligomers, considered as model compounds of poly(ether-ketone-ketone), was studied by means of dielectric spectroscopy. The dynamics of the α relaxation of ether-ketone model compounds as compared with that of poly(arylether-ketone-ketone) (PEKK) (50/50), shows up differences which can be attributed to the variation of inter- and intramolecular correlations with the chain length. Model compounds exhibit a nearly similar degree of cooperativity regardless the differences in Tg values. The PEKK (50/50) polymer exhibits stronger cooperativity than the oligomers suggesting that in poly(ether-ketone-ketone)s molecular motions above Tg extend to more than one monomeric unit.

Study of oligo(aryl ether ketone)s as models for aromatic polyketones

Full Paper: The thermal properties and crystal chain packing found for two series (m and p) of oligomeric compounds, with n = 5, 7, 9, and 11 phenylene units, as model compounds for aromatic polyketones are reported. While oligomers of series p contain 1-4 substituted phenylene units those of series m contain an isophthalic group (1-3 substituted phenylene) as the central aryl unit. The keto/ether mole ratio ranges from 0.5 to 0.75. It is confirmed that melting temperatures are clearly dependent on the keto/ether mole ratio as well as on the presence of the isomer defect (isophthalic ring). The keto/ether mole ratio also influences the molecular cross-section and the fusion enthalpy of crystals. Analysis of X-ray diffractograms of the powder samples reveals the presence of lamellar crystals with a thickness corresponding to the length of the linear extended molecular conformation (c axis). Molecular compounds of series p crystallize in the more stable crystal polymorph (form I), observed for aromatic polyketones, while oligomers of series m show polymorphism depending on their chain length. A partial polymeric character of the longest compounds (n = 11) of the two m and p series was found. Nevertheless, their inclusion in this structural study seems to be pertinent.

Synthesis of novel polyaryl(ether–ketones) with tert‐butyl pendent groups

Linear polyaryl(ether ketones) containing tert-butyl pendent groups were prepared from aromatic hydrocarbons and aromatic diacid chlorides, both classes of monomers containing tert-butyl pendent groups. The polymers were prepared in high yield and high molecular weight by low-temperature precipitation polycondensation in 1,2-dichloroethane. The presence of meta-oriented moieties and bulky pendent groups played a beneficial role with regard to solubility, while the thermal transitions and thermal resistance were not greatly impaired relative to conventional all para-oriented polyaryl(ether-ketones). The current polyaryl(ether-ketones) showed glass transition temperatures in the range 170-240°C and decomposition temperatures, as measured by TGA, of about 500°C.

The relationship between nonexponential relaxation and molecular stiffness in aromatic model compounds

The α relaxation of a series of ether–ketone model compounds was studied to quantify the effect of molecular stiffness on the Kohlrausch–Williams–Watts stretching exponential. The obtained values decrease with increasing stiffness and are within the theoretical bounds predicted for systems with spatial dimensionality varying from 2 to 1.

Synthesis of Poly(1,4-Phenylene-Oxy-1,4-Phenylene-Carbonyl-1,3-Phenylene-Carbonyl)S (M-Pekk) by Precipitation Polycondensation

High molecular weight m-substituted poly(ether ketone-ketone) has been synthesized by electrophilic precipitation polycondensation via two different ways: reaction of isophthaloyl chloride with diphenyl ether and reaction of isophthaloyl chloride with 1,3-bis(4-phenoxybenzoyl)benzene. The second way of synthesis was found to give structurally more perfect polymers with higher molecular weights. In both cases polycondensation proceeded with precipitation of the polymers formed as uniform particles. The influence of reaction conditions has been studied. Monomer concentration and monomer stoichiometric ratio were shown to affect the polymer properties.