Azodibenzoyl Chloride Research Articles

Synthesis and characterization of polyesters based on diethylketone moiety

A new class of unsaturated polyesters based on diethylketone have been prepared by interfacial polymerization of 2,4-bis(4-hydroxybenzylidene)-3-pentanone (I) and 2,4-bis(4-hydroxy-3-methoxybenzylidene)-3-pentanone (II) with 4,4′-azodibenzoyl chloride and 3,3′-azodibenzoyl chloride at ambient temperature. The model compounds were synthesized by reaction of (I) and (II) with benzoyl chloride. The new monomers, model compounds and polyesters have been characterized by different spectral analyses. The polyesters have inherent viscosity of 0.55–0.80 dL/g and moderate number average molecular weight (M n) in the range of 6150–7400 g/mol. Most of the compounds exhibited their solubility in aprotic solvents while partial solubility in various halogenated organic solvents was observed. The temperatures of 10% weight loss were high (225–330 °C) in nitrogen, indicating that these polyesters have excellent thermal stability. Doping with iodine dramatically raised the conductivity and produced brown colored semiconductive polymers with a maximum conductivity of 2.7 × 10−6 Ω−1cm−1. Moreover, the morphological properties of selected example of polyesters were detected by SEM.

Novel self-dyed wholly aromatic polyamide–hydrazides covalently bonded with azo groups in their main chains

Thermal characteristics of several novel self-dyed wholly aromatic polyamide–hydrazides covalently bonded with azo groups in their main chains and containing o-hydroxy group as a substituent group in the aryl ring of the aminohydrazide part of the polymers have been investigated in nitrogen and in air atmospheres using differential scanning calorimetry, thermogravimetric analyses, infrared spectroscopy, and elemental analyses. The effect of introducing different predetermined proportions of para- and meta-phenylene moieties into the backbone chain of the polymers on their thermal characteristics has been evaluated. Azopolymers having different molecular masses of all para-oriented phenylene type units were also thermally characterized. These polymers were prepared by a low temperature solution polycondensation reaction of either 4-amino-3-hydroxybenzhydrazide or 3-amino-4-hydroxybenzhydrazide with an equimolar amount of either 4,4′-azodibenzoyl chloride (4,4′ADBC), 3,3′-azodibenzoyl chloride (3,3′ADBC), or mixtures of various molar ratios of 4,4′ADBC and 3,3′ADBC in anhydrous N,N-dimethyl acetamide containing 3 % m v−1 LiCl as a solvent at −10 °C. All the polymers have the same structural formula except the mode of linking phenylene units in the polymer chain. The content of para- and meta-phenylene moieties was varied within these polymers so that the changes in the latter were 10 mol% from polymer to polymer, starting from an overall content of 0–100 mol%. The results reveal that these polymers are characterized by high thermal stability and could be cyclodehydrated into linear aromatic polymers with alternating 1,3,4-oxadiazole and benzoxazole structural units within the same polymer approximately in the region of 200–480 °C, either in nitrogen or in air atmospheres by losing water from the hydrazide and o-hydroxybenzamide groups, respectively. Along with the cyclodehydration, the polymer may lose molecular nitrogen from the azo groups. This is not a true degradation, but rather a thermo-chemical transformation reaction of the evaluated polymers into the corresponding poly(1,3,4-oxadiazolyl-benzoxazoles). The resulting poly(1,3,4-oxadiazolyl-benzoxazoles) start to decompose in the temperature range above 330–560 °C, either in nitrogen or in air atmospheres without mass loss at a lower temperature. The thermal and thermo-oxidative stabilities of the polymers are affected by the nature and amount of arylene groups incorporated into their chains, being higher for polymers with greater content of para-oriented phenylene rings, which permits more interchain hydrogen bonds as a result of greater chain symmetry, packing efficiency, and rod-like structure. Increasing the content of para-oriented phenylene rings leads to a strong improvement in both the initial decomposition temperature as well as in the residual mass at a particular temperature. The stability of the polymers was found to be independent of their molecular masses. This confirms that high thermal stability is not a polymer property which would depends upon the length of its macromolecular chains, but rather upon its chemical structure in which all and every atomic group contributes by its own thermal stability to the macroscopic properties of the whole polymer.

Novel Self-Dyed Wholly Aromatic Polyamide-Hydrazides Covalently Bonded with Azo Groups in Their Main Chains: 1. Structure-Property Relationships

Twelve novel intrinsically colored wholly aromatic azopolyamide-hydrazides containing various proportions of para- and meta-phenylene units were successfully synthesized by a low temperature (−10 °C) solution polycondensation reaction of either 4-amino-3-hydroxybenzhydrazide (4A3HBH) or 3-amino-4-hydroxybenzhydrazide (3A4HBH) with an equimolar amount of either 4,4′-azodibenzoyl chloride (4,4′ADBC), 3,3′-azodibenzoyl chloride (3,3′ADBC), or mixtures of various molar ratios of 4,4′ADBC and 3,3′ADBC in anhydrous N,N-dimethyl acetamide (DMAc) containing 3% (wt/v) LiCl as a solvent. The structures of the polymers were proven by elemental analysis, FTIR, 1H- and 13C-NMR spectroscopy. The polymers’ properties were strongly affected by their various structures. The intrinsic viscosities of the polymers were ranged from 0.7 to 4.75 dL g−1 and increased with the para-phenylene units content. The polymers are partially soluble in DMAc, dimethyl formamide (DMF) and N-methyl-2-pyrrolidone (NMP). Their solubility increases with the introduction of meta-phenylene moieties into the polymer chains. The polymers exhibit a great affinity for water sorption. Their hydrophilicity increases as a function of the content of meta-phenylene rings incorporated into the polymer. Mechanical properties of the polymer films are improved markedly by substitution of para-phenylene units for meta-phenylene units. The completely para-oriented type polymer has the best thermal and thermo-oxidative stability relative to those of the other polymers.

Activation Energy from Thermogravimetric Analysis of Certain Azopolyamides

Six new azopolyamides were synthesized from 2, 21–dimethoxy 4, 41–diaminoazobenzene [Benzenamine–(3, 31– dimethoxy–4, 41-azo) bis] condensed with any one of the following diacid chlorides viz. (i) terephthaloyl chloride. (ii) isophthaloyl chloride. (iii) 4, 41–azodibenzoyl chloride (iv) 3, 31-azo dibenzoyl chloride (v) 4, 41–stilbene dicarbonyl chloride and (vi) 4, 41–oxydibenzoyl chloride using low temperature solution method. These polyamides were characterized by thermogravimetric analyses (TGA and DTA). Activation energy has been calculated using Murray and white, coats and Redfern, Doyle's, Freeman and Carroll, Ozawa–Flyn–Waal's and modified Coats and Redfern's method.

Thermal stability and degradation behavior of novel wholly aromatic azopolyamide-hydrazides

Thermal stability and degradation behavior of a series of novel wholly aromatic polyamide-hydrazides containing azo groups in their main chains have been investigated in nitrogen and in air atmospheres using differential scanning calorimetry (DSC), thermogravimetry (TG), infrared spectroscopy (IR) and elemental analysis. The influences of controlled structural variations and molecular weight on the thermal stability and degradation behavior of this series of polymers have also been studied. The structural differences were achieved by varying the content of para- and meta-substituted phenylene rings incorporated within this series. Azopolyamide-hydrazides having different molecular weights of all para-substituted phenylene type units were also examined. The polymers were prepared by a low temperature solution polycondensation reaction of p-aminosalicylic acid hydrazide [PASH] and an equimolar amount of 4,4′-azodibenzoyl chloride [4,4′ADBC] or 3,3′-azodibenzoyl chloride [3,3′ADBC] or mixtures of various molar ratios of 4,4′ADBC and 3,3′ADBC in anhydrous N, N-dimethyl acetamide [DMAc] containing lithium chloride as a solvent at −10 °C. All the polymers have the same structural formula except the mode of linking phenylene units in the polymer chain. The results clearly reveal that these polymers are characterized by high thermal stability. Their weight loss occurred in three distinctive steps. The first was small and assigned to the evaporation of absorbed moisture. The second was appreciable and was attributed to the cyclodehydration reaction of the hydrazide groups into 1,3,4-oxadiazole rings by losing water, combined with elimination of azo groups by losing molecular nitrogen. This is not a true degradation but rather a thermo-chemical transformation reaction of the azopolyamide-hydrazides into the corresponding polyamide-1,3,4-oxadiazoles. The third was relatively severe and sharp, particularly in air, and corresponded to the decomposition of the resulting polyamide-1,3,4-oxadizoles. In both degradation atmospheres, the improved resistance to high temperatures was always associated with increased content of para-phenylene moieties of the investigated polymer. The better thermal stability of the wholly para-oriented type of polymer relative to the other polymers is attributed to its greater chain symmetry which is responsible for its greater close packing, rod-like structure and consequently stronger intermolecular bonds which would be more difficult to break and therefore more resistance to high temperatures. Further, with exception of 160–200 °C temperature range, where the lower molecular weight samples showed considerable weight losses which were most probably due to hydrogen bonded DMAc, all the wholly para-oriented phenylene type of polymer samples behaved similarly regardless of their respective molecular weight. This seems to indicate that the structural building units responsible for high thermal stability of the polymers are their characteristic groups, such as aromatic moieties, amide and hydrazide linkages in case of azopolyamide-hydrazides, and 1,3,4-oxadiazole rings, aromatic nuclei and amide linking bonds in case of polyamide-1,3,4-oxadiazoles, rather than the longer chain segments.

Synthesis and characterization of novel wholly aromatic azopolyamide-hydrazides

The influence of controlled structural variations upon the physical, thermal and mechanical properties of a series of novel wholly aromatic azopolyamide-hydrazides has been investigated. The polymers were prepared by a low temperature solution polycondensation reaction of p-aminosalicylic acid hydrazide (PASH) and an equimolar amount of either 4,4′-azodibenzoyl chloride (4,4′ADBC), 3,3′-azodibenzoyl chloride (3,3′ADBC), or their appropriate combinations in anhydrous N, N-dimethyl acetamide (DMAc) as solvent at −10 °C. The content of para-/ meta-phenylene units was varied within this series between 50/50 and 100/0. Polymer structures were characterized by elemental analysis and infrared spectrometry. Polymer properties were evaluated by intrinsic viscosity, solubility, moisture regain, thermal and thermo-oxidative stability, mechanical properties and X-ray diffraction. The results obtained during the preparation of these polymers, their subsequent structural characterization and their property evaluations are discussed. All the polymers have the same structural formula except the way of linking phenylene units inside the polymer chain. The polymers intrinsic viscosities were ranged from 1.5 to 4.3 dl g −1 in DMAc/3% LiCl at 25 ± 0.1 °C and increased with the increase of para-phenylene units content. The polymers are found to be partially soluble in polar aprotic solvents like DMAc, dimethyl formamide [DMF], and N-methyl pyrrolidone (NMP) at room temperature. Their solubilities in these solvents were found to be enhanced remarkably by adding LiCl and their solutions could be cast into flexible films. All the polymers dissolved freely in concentrated sulphuric acid but with degradation. The polymers having para-linkages in this series are less soluble than the polymers having meta-linkages. The prepared polymers exhibit a great affinity to water sorption. The hydrophilic character increases as a function of meta-phenylene rings content incorporated into the polymer. Thermogravimetric measurements indicated that the perfectly p-oriented type of polymer has better thermal and thermo-oxidative stabilities relative to that of the other polymers. Mechanical properties of the polymers films are improved markedly with introduction of para-phenylene nuclei into the polymers. All these polymers were found to be amorphous as confirmed by X-ray diffraction.

New polyamides containing azobenzene unites and hydantoin derivatives in main chain: synthesis and characterization

Eight new polyamides containing azo moieties and hydantoin groups were synthesized under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of 4,4 ′-azodibenzoyl chloride [4,4 ′-azobenzenedicarboxylic acid] 3 with eight different derivatives of 5,5-disubstituted hydantoin 4a–h in the presence of a small amount of a polar organic medium such as o-cresol. The polycondensation proceeded rapidly, compared with the bulk polycondensation and the solution polycondensation and was completed between 7–12 min, producing a series of new polyamides 5a–h in high yield, and inherent viscosity between 0.35 and 0.60 dL/g. The resulting polyamides were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis (TGA and DTG), solubility test and FT-IR spectroscopy. All of the polymers were soluble at room temperature in polar solvents such as N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, tetrahydrofurane and N-methyl-2-pyrrolidone.

Synthesis and characterization of new unsaturated polyesters and copolyesters containing azo groups in the main chain

A new interesting class of linear unsaturated polyesters based on dibenzylidenecycloalkanones have been synthesized by interfacial polycondensation of 4,4 ′-azodibenzoyl chloride or 3,3 ′-azodibenzoyl chloride with: 2,5-bis( p-hydroxybenzylidene)cyclopentanone I, 2,6-bis( p-hydroxybenzylidene)cyclohexanone II, 2,6-divanillylidenecyclohexanone III, or 2,7-bis( p-hydroxybenzylidene)cycloheptanone IV at ambient temperature. The copolyesters are also synthesized from the monomers I, II, III or IV with the diacid chlorides. The resulting polyesters and their copolyesters were characterized by elemental analyses, IR spectroscopy and solubility. Additionally, inherent viscosity of the polyesters in the range 0.32–0.86 dL g −1 and the inherent viscosity of the copolyesters in the range 0.28–0.65 dL g −1 were determined. The UV–visible spectra of certain polymers were measured in m-cresol solution and showed a characteristic absorption band at 435–473 nm due to n–π * transition. The thermal properties of the polymers were evaluated by thermo gravimetric analysis and differential scanning calorimetry measurements and correlated with their structural units. The crystallinity of some polyesters and copolyesters were tested. In addition, the electrical properties of all polyesters and copolyesters were measured.

New Polymer Syntheses IV. Synthesis and Characterization of New Polyamides Containing Bis-Benzthiazolyl Sulphone Units in the Main Chain

Bis(2-aminobenzthiazolyl) sulphone (BABS) was used as a new starting material for preparing polyamides. These polyamides were prepared by reacting BABS with adipoyl, sebacoyl, isophthaloyl and terephthaloyl dichlorides, and also with 4,4′-azodibenzoyl chloride or 3,3′-azodibenzoyl chloride, utilizing the solution polycondensation technique at low temperature. In addition, the model compound was synthesized by condensing the BABS with benzoyl chloride. Characterization of the monomer, model compound and the polyamides was accomplished by 1H NMR, IR and elemental analyses. The polyamides had reduced viscosities of 0.25–0.63 dI/g in DMF or DMSO at 25 °C. All the polymers dissolved readily at room temperature in polar aprotic solvents. The thermal stability of the polymers was evaluated by TGA and DSC measurements.

New polymer syntheses II--linear unsaturated polyesters containing azo groups*

Linear unsaturated polyesters, characterized by the presence along the polymer chain of azo groups between aromatic rings, have been prepared by reacting 3,5-bis(p-hydroxybenzylidene)isopropyl piperidinone (BHIP, I) or 3,5-divanillylidene isopropylpiperidinone (DVIP, It) with 4,4'-azodibenzoyl chloride (III) and 3,3'-azodibenzoyl chloride (IV) using the interfacial polycondensation method. The polymers were characterized by elemental analyses. IR spectroscopy, solubility and viscomnetry. The thermal properties of the polymers were evaluated by thermogravimetric analysis (TGA) and correlated to their structural units. Al] the polymers dissolved readily in concentrated H2S04 or o-cresol. X-ray analysis of the polymers showed some degree of crystallinity in polymers VI and VII. Moreover, the UV-visible spectra of certain polymers were measured in NMP or in dimethyl suiphoxide (DMSO)solutions and showed characteristic absorption bands at 412 and 432 nrn due to n-7r* transition.

Arylidene Polymers. XVI. Synthesis, Characterization, and Morphology of New Polyesters of Diarylidenecycloheptanone Containing Azo and Azomethine Groups in the Main Chain

Abstract A new class of linear unsaturated polyesters of diarylidenecyclo-heptanone containing azo or azomethine groups in the polymer main chain has been synthesized by interfacial polycondensation of 4,4′-azodibenzoyl chloride, 3,3′-azodibenzoyl chloride, and 4,4′[1,4-phenylene bis(methylidenenitrilo)]dibenzoyl chloride with 2,7 bis(p-hydroxybenzylidene)cycloheptanone at ambient temperature. The resulting polyesters were characterized by elemental analyses, IR spectroscopy, solubility, and viscometry measurements. The thermal properties of the polymers were evaluated by TGA and DTA measurements. The crystallinity of the polymers was examined by x-ray analysis. The morphology of a high performance polyester, namely poly[oxycarbonyl-3,3′-azobenzenecar-bonyloxy-p-phenylene-methylidyne (2-oxo-1,3-cycloheptanediylidene) methylidyne-p-phenylene], has been investigated by scanning electron microscopy. The UV-visible spectra of polymers V and VI were measured in m-cresol solution and showed characteristic absor...

Arylidene Polymers VII. Synthesis and Characterization of New Polyesters of Diarylidenecycloalkanones Containing an Azo Group in the Main Chain

A new interesting class of linear, unsaturated polyesters based on diarylidenecycloalkanones containing an azo linkage in the polymer main chain have been synthesized by interfacial polycondensation of 4,4′-azodibenzoyl chloride or 3,3′-azodibenzoyl chloride with 2,5-bis(p-hydroxybenzylidene)cyclopentanone, 2,5-divanillylidenecyclopentanone, 2,6-bis(p-hydroxybenzylidene)cyclohexanone and 2,6-divanillylidenecyclohexanone at ambient temperature. The resulting polyesters were characterized by elemental analyses, IR spectroscopy, solubility and viscometry measurements. The thermal properties of the polymers were evaluated by TGA and DSC measurements and correlated to their structural units. X-ray analysis of the polymers showed that polyesters based on the meta azo linkage were totally amorphous whereas, polyesters with the para azo linkage had some degree of crystallinity. The UV-visible spectra of certain polymers were measured in m-cresol solution and showed a characteristic absorption band at 438-465 nm due to n-π* transition. In addition, the electrical properties of all polyesters were measured.