Synthesis and characterization of novel wholly para‐oriented aromatic polyamide‐hydrazides containing sulfone‐ether linkages

Four novel wholly para‐oriented aromatic polyamide‐hydrazides containing flexibilizing sulfone‐ether linkages in their main chains have been synthesized from 4‐amino‐3‐hydroxy benzhydrazide (4A3HBH) with either 4,4′‐sulfonyldibenzoyl chloride (SDBC), 4,4′‐[sulfonylbis(1,4‐phenylene)dioxy]dibenzoyl chloride (SODBC), 4,4′‐[sulfonylbis(2,6‐dimethyl‐1,4‐phenylene)dioxy]dibenzoyl chloride (4MeSODBC), or 4,4′‐(1,4‐phenylenedioxy)dibenzoyl chloride (ODBC) via a low‐temperature solution polycondensation reaction. A polyamide‐hydrazide without the flexibilizing linkages is also investigated for comparison. It was synthesized from 4A3HBH and terephthaloyl chloride (TCl) by the same synthetic route. The intrinsic viscosities of the polymer ranged from 2.85 to 4.83 dL g^?1 in N,N‐dimethyl acetamide (DMAc) at 30°C and decreased with introducing the flexibilizing linkages into the polymer. All the polymers were soluble in DMAc, N,N‐dimethyl formamide (DMF), and N‐methyl‐2‐pyrrolidone (NMP), and their solutions could be cast into films with good mechanical strengths. Further, they exhibited a great affinity to water sorption. Their solubility and hydrophilicity increased remarkably by introducing the flexibilizing linkages. The polymers could be thermally cyclodehydrated into the corresponding poly(1,3,4‐oxadiazolyl‐benzoxazoles) approximately in the region of 295–470°C either in nitrogen or in air atmospheres. The flexibilizing linkages improve the solubility of the resulting poly(1,3,4‐oxadiazolyl‐benzoxazoles) when compared with poly(1,3,4‐oxadiazolyl‐benzoxazoles) free from these linkages. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and photo-induced transformation of helical aromatic polyamides consisting of axially dissymmetric biphenylene joints and azobenzene segments in the backbone

Wholly aromatic polyamides having a novel helical structure were prepared by the reaction of axially dissymmetric (R)- or (S)-6,6′-dimethylbiphenyl-2,2′-dicarbonyl chloride with aromatic diamines, which are soluble in common solvents such as tetrahydrofuran and N,N-dimethylformamide. Photo-irradiation of a tetrahydrofuran solution of the polymer obtained with 4,4′-diaminoazobenzene induced a change of the helical conformation because of the trans–cis isomerization of the azobenzene units in the polymer chain. No change in the specific rotation of the polymer was observed on heating at 100°C for 4h, indicating thermal stability of its helical structure. CD spectra showed that the helical conformation was maintained in methanesulphonic acid. © 1998 SCI.     

Aromatic polyesters (polyarylates) containing arylene sulfone ether linkages

A series of soluble aromatic polyesters (polyarylates) containing arylene sulfone ether linkages and having inherent viscosities of 0.36–1.10 dl/g were prepared by the two-phase low temperature polycondensation of 4,4′-[sulfonyl-bis(p-phenyleneoxy)]dibenzoyl chloride and 3,3′-[sulfonylbis(p-phenyleneoxy)]-dibenzoyl chloride with various bisphenols in an organic solvent-aqueous alkaline solution system in the presence of a phase transfer catalyst. Bisphenols 4,4′-[sulfonylbis(p-phenyleneoxy)]diphenol and 3,3′-[sulfonylbis(p-phenyleneoxy)]-diphenol were synthesized in quantitative yields by an improved procedure. The aromatic polyesters prepared were characterized by infrared spectroscopy, elemental analysis, solution viscosity, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction. The polyesters prepared had glass transition temperatures in the range 150–230°C and initial decomposition temperatures of 397–491°C. They gave transparent, tough and flexible films by the solution casting technique.     

Novel composite nanofibers based on polyamide 66/graphene oxide- grafted aliphatic- aromatic polyamide: preparation and characterization

New polyamide 66/graphene oxide (GO)-grafted aliphatic-aromatic polyamide (polyamide-imide) (PAI) (PA66/GOF) composites nanofibers were successfully prepared via electrospinning method for the first time. An polyamide imide (PAI) was synthesized using polycondensation reaction from a dicarboxylic acid and a diamine based on 4,4′-(4,4′-isopropylidenediphenyl-1,1′-diyldioxy) dianiline, and characterized by ¹HNMR and FTIR. Morphological, structural, thermal and mechanical characteristics of the nanocomposite fibers were investigated by means of SEM, TEM, WAXD, DMTA and TGA techniques. Composites nanofibers of PA66/GO, PA66/PAI and PA66/GOF with smooth surface, uniform structure as well as with diameter ranging from 195 to 784 nm were obtained. The GO incorporation caused a reduction in the nanofibers diameters. The TEM images showed that the GO was well dispersed in the PA66 nanofibers without significant aggregation. An approximately 10 °C temperature increase in the glass transition temperature of PA66 was achieved by addition of 0.5 wt% of PAI, resulting from aliphatic-aromatic structure of PAI. By the TGA results, an increase about 40 °C was observed in the thermal stability of PA66/PAI composite nanofibers in comparison with that of pure PA66 nanofibers.     

Permselectivities of 2,2′‐dimethyl‐4,4′‐bis(aminophenoxyl)biphenyl diphenyl methane–based aromatic polyamide membranes for aqueous alcohol mixtures in pervaporation and evapomeation

The separation of aqueous alcohol mixtures was carried out by use of a series of novel aromatic polyamide membranes. The aromatic polyamides were prepared by the direct polycondensation of 2,2′‐dimethyl‐4,4′‐bis(aminophenoxyl)biphenyl (DBAPB) with various aromatic diacids, such as terephthalic acid (TPAc), 5‐tert‐butylisophthalic acid (TBPAc), and 4,4′‐hexafluoroisopropylidenedibenzoic acid (FDAc). The pervaporation and evapomeation performance of these novel aromatic polyamide membranes for dehydrating aqueous alcohol solution were investigated. The solubility of ethanol in the aromatic polyamide membranes is higher than that of water, but the diffusivity of water through the membrane is higher than that of ethanol. The effect of diffusion selectivity on the membrane separation performances plays an important role in the evapomeation process. Compared with pervaporation, evapomeation effectively increases the permselectivity of water. Moreover, the effect of aromatic diacids on the polymer chain packing density, pervaporation, and evapomeation performance were investigated. It was found that the permeation rate could be increased by introduction of a bulky group into the polymer backbone. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2688–2697, 2003     

Synthesis of thermostable polyamideimides and their properties

Thermostable polyamideimides with inherent viscosity of 1.02–1.50 dL/g were synthesized from reacting of diamine-terminated aromatic amide prepolymer with various diisocyanate terminated imide prepolymers. The imide prepolymer was prepared by using 4,4′-diphen-ylmethane diisocyanate to react with 3,3′,4,4′ benzophenonetetracarboxylic dianhydride, 3,3′,4,4′ sulfonyl diphthalic anhydride, or 4,4′-oxydiphthalic anhydride using the direct one-pot method to improve their solubility. Almost all of the polyamideimides were generally soluble in a wide range of organic solvents such as N,N-dimethylformamide, N,N-dimeth-ylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and pyridine at room temperature. Polymers with high imide content required high temperatures to dissolve. All polyamide-imides had a glass transition temperature of 223–352°C and showed a 10% weight loss temperature of 415–575°C in air and 424–583°C in nitrogen atmosphere. The tensile strength, elongation at break, and initial modulus of polymer films ranged from 61 to 108 MPa, 5 to 10% and 1.54 to 2.50 GPa, respectively. These copolymers were partly crystalline in structure as shown by X-ray pattern. © 1996 John Wiley & Sons, Inc.     

Preparation and properties of organo‐soluble polyimides based on 4,4′‐diamino‐3,3‐dimethyldiphenylmethane and conventional dianhydrides

4,4′‐Diamino‐3,3′‐dimethyldiphenylmethane was used to prepare polyimides in an attempt to achieve good organo‐solubility and light color. Polyimides based on this diamine and three conventional aromatic dianhydrides were prepared by solution polycondensation followed by chemical imidization. They possess good solubility in aprotonic polar organic solvents such as N‐methyl 2‐pyrrolidone, N,N‐dimethyl acetamide, and m‐cresol. Polyimide from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and diphenylether‐3,3′,4,4′‐tetracarboxylic acid dianhydride is even soluble in common solvents such as tetrahydrofuran and chloroform. Polyimides exhibit high transmittance at wavelengths above 400 nm. The glass transition temperature of polyimide from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and pyromellitic dianhydride is 370°C, while that from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and diphenylether‐3,3′,4,4′‐tetracarboxylic acid dianhydride is about 260°C. The initial thermal decomposition temperatures of these polyimides are 520–540°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1299–1304, 1999     

Synthesis and properties of polyimides derived from diamine monomer containing bi-benzimidazole unit

A new aromatic heterocyclic diamine monomer containing bi-benzimidazole unit, 2,2-bis(4′-aminophenyl)-5,5-bi-1H-benzimidazole, was synthesized from 2,2-bis(4′-nitrophenyl)-5,5-bi-1H-benzimidazole (BNPBBI) prepared via the reaction of 3,3′,4,4′-biphenyltetramine and p-nitrobenzaldehyde with a high yield. Their compositions and chemical structures containing polybenzimidazole backbone were characterized by FTIR, ¹H NMR and elemental analysis. A series of aromatic polyimides containing the heterocyclic moiety in the main chain were prepared by the reaction of BAPBBI with various aromatic dianhydrides of 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride or pyromellitic dianhydride. The polymers possess a high glass transition temperature of >415 °C and a good thermal stability up to 566 °C with a 5 % weight loss. The combination of polybenzimidazole and polyimide via introducing BAPBBI into the main chains provides the rigid structure, and macromolecular interactions are thus enhanced, resulting in the outstanding mechanical properties. These polyimides exhibit the strong tensile strength of 201 to 327 MPa, and the ultrahigh tensile moduli of 10.7 to 15.5 GPa without post stretching.     

Synthesis of thermally stable aromatic poly(imide amide benzimidazole) copolymers

3,3′‐Dinitrobenzidine was first reacted with excess m‐chlorophenyl acid to form a monomer with dicarboxylic acid end groups. Two types of aromatic dianhydrides (Pyromellitic diconhydride (PMDA) and 3,3′,4,4′‐sulfonyl diphthalic anhydride) were also reacted with excess 4,4′‐diphenylmethane diisocyanate to form polyimide prepolymers terminated with isocyanate groups. The prepolymers were further extended with the diacid monomer to form nitro groups containing aromatic poly(imide amide). The nitro groups in these copolymers were hydrogenated to form amine groups and then were cyclized at 180°C to form poly(imide amide benzimidazole) in poly(phosphoric acid), which acted as a cyclization agent. The resultant copolymers were soluble in sulfuric acid and poly(phosphoric acid), in sulfolane under heating to 100°C, and in the polar solvent N‐methyl‐2‐pyrrolidone under heating to 100°C with 5% lithium chloride. According to wide‐angle X‐ray diffraction, all the copolymers were amorphous. According to thermal analysis, the glass‐transition temperatures of the copolymers were 270–322°C. The 10% weight‐loss temperatures were 460–541°C in nitrogen and 441–529°C in air. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1435–1444, 2003     

Synthesis of high refractive index polyamides containing thioether unit

Two kinds of aromatic dibenzoyl chloride monomer containing thioether unit 4,4′-Bis(4-chloroformylphenylthio)benzophenone (BP-DC) and 4,4′-thiodibenzoyl chloride (T-DC) were synthesized with two steps, which was reacted with diamine monomer containing thioether and amide unit to prepare a new kind of polyamide containing high quantity thio-ether group. The intrinsic viscosity of the polyamides was 0.76–0.90 dl/g obtained with optimum synthesis conditions. The polymers were found to have good optical properties: the optical transmittance of the aromatic polyamide film at 450 nm is higher than 80%, meantime the high quantity thio-ether unit provided the polymer with a high refractive index ranging from 1.691 to 1.696 and low birefringence of 0.007–0.008. At the same time the polymers had excellent thermal performance with glass transition temperature (T_g) of 226 °C–278 °C, initial degradation temperature (T_d) of 427 °C–439 °C. They showed improved solubility in polar aprotic solvents.     

Synthesis and characterization of new thermally stable aromatic copoly(ester–amide)s from diester‐dicarboxylic acids

Two new aromatic diester‐dicarboxylic acids containing furan rings, namely, benzofuro[2,3‐b]benzofuran‐2,9‐dicarboxyl‐bis‐pyridyl ester‐4,4′‐dicarboxylic acid and benzofuro[2,3‐b]benzofuran‐2,9‐dicarboxyl‐bis‐phenyl ester‐4,4′‐dicarboxylic acid were synthesized by the reaction of benzofuro[2,3‐b]benzofuran‐2,9‐dicarbonyl chloride with 6‐hydroxynicotinic acid and 4‐hydroxybenzoic acid, respectively. These monomers were converted to aromatic copoly(ester–amide)s by reaction with various aromatic diamines via direct polycondensation. Polymers were characterized by FTIR and ¹H NMR spectroscopy, thermogravimetry, viscosity and solubility tests. The inherent viscosity of the polymers was in the range 0.23–0.46 dl g^?1 in dimethyl sulfoxide at 30 °C. They dissolved readily in polar solvents at room temperature. They possess a glass‐transition temperature in the range 210–260 °C and exhibit excellent thermal stability. Copyright © 2004 Society of Chemical Industry     

Reduction and cyclization to form poly(benzimidazole amide imide) copolymers

Poly(amide imide) copolymers were synthesized with different molar ratios of 4,4‐diphenylmethane diisocyanate, two types of aromatic dianhydrides (pyromellitic dianhydride (PMDA) and 3,3′,4,4′‐sulfonyl diphthalic anhydride (DSDA)), and a diacid, which was derived from 3,3′‐dinitrobenzidine and isophthaloyl chloride in a previous work. In this study, the copolymers were further reacted with a reducing agent, and the nitro groups in the copolymers were hydrogenated into amine groups. Then, the amine‐group‐containing poly(amide imide) copolymers were cyclized at 180°C to form the poly(benzimidazole imide amide) copolymers in poly(phosphoric acid), which acted as a cyclizing agent. The resultant copolymers were soluble in sulfuric acid and poly(phosphoric acid) at room temperature and in sulfolane or N‐methyl‐2‐pyrrolidone under heating to 100°C with 5% lithium chloride. According to wide‐angle X‐ray diffraction, all the copolymers were amorphous. According to thermal analysis, the glass‐transition temperature ranged from 270 to 322°C, and the 10% weight‐loss temperature ranged from 460 to 541°C in nitrogen and from 441 to 529°C in air. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 378–386, 2004     

Synthesis and the properties of novel cycloaliphatic-aromatic polyamides having pendent N,N'-diphenyl imido groups

: We have investigated a novel monomer having two pendent phenyl imido groups for preparing new cycloaliphatic-aromatic polyamides. Novel polyamides were synthesized by direct polycondensation reaction of N,N'-diphenyl-2,3,5,6-diimido cyclohexane-1,4-dicarboxylic acid(PICA) and various aromatic diamines such as p-phenylene diamine, 4,4'-oxydianiline and 4,4'-methylene dianiline. A direct polycondensation was carried out by a Yamazaki method which is typical of using triphenyl phosphite, lithium chloride, and pyridine. Inherent viscosity of these resulting polyamides are ranged 0.20 ∼ 0.45 dl/g. A transparent flexible and tough film was casted. The glass transition temperature of the polyamide from the PICA and 4,4'-oxydianiline is 147 °C. The decomposition temperature of these polyamides are ranged from 350 ∼ 360 °C and the ash contents of them orders MDA > p-PDA > ODA according to kinds of the using diamines. And the solubilities of these polyamides are good in aprotic solvents such as DMAc, NMP, DMF. Received: 26 July 1999/Revised version: 14 September 1999/Accepted: 28 September 1999     

High temperature laminating resins based on maleimido end-capped pyromellitimide

A novel class of bismaleimides, biscitraconimides, and bisdichloromaleimides chain-extended by pyromellitimide was prepared and characterized by infrared and proton nuclear magnetic resonance spectroscopy. These polymer precursors were prepared by reacting maleic/citraconic/dichloromaleic anhydride (1 mol) with an equimolar amount of a diamine and subsequently with pyromellitic dianhydride (0.5 mol). The tetraamic acid formed was cyclodehydrated by chemical or thermal means. The curing behavior of polymer precursors was investigated by differential thermal analysis. Bismaleimide was thermally polymerized at a relatively higher temperature than the corresponding biscitraconimide and at lower temperature than bisdichloromaleimide. The curing temperature of monomers fluctuated between 209 and 318°C. Dynamic thermogravimetric analysis of the cured aromatic resins showed that they were approximately stable up to 370°C both in nitrogen and air. Their char yield was 53–63% at 800°C under anaerobic conditions. The relative thermal stability of the cured resins, with respect the diamine utilized for imidization, was of the order p-phenylenediamine > 4-aminophenyl ether > 4,4′-diaminodiphenylmethane > 4,4′-diaminodiphenylsulfone > hexamethylenediamine. In addition, the thermal and thermooxidative stability of polymers was ascertained by isothermal gravimetric analysis.     

Synthesis and photoinduced transformation of helical aromatic polyamides containing atropisomeric biphenylene units and azobenzene segments in the main chain

Optically active helical polyamides were synthesized by condensation of axially dissymmetric (R)‐ or (S)‐6,6′‐diamino‐2,2′‐dimethylbiphenyl with aromatic dicarbonyl chlorides. The wholly aromatic polyamides obtained were soluble in various low‐polarity organic solvents such as tetrahydrofuran and chloroform, as well as in polar N,N‐dimethylacetamide. Excellent thermal stability of the helical structure was observed for the polyamide obtained with 4,4′‐dicarbonylbiphenyl chloride in refluxing N,N‐dimethylacetamide. Chiroptical data obtained from the circular dichroism spectra showed that the helical conformation of the polyamide containing azobenzene segments in the main chain can be transformed reversibly on irradiation with UV–visible light because of the trans–cis isomerization of the segments. Copyright © 2004 Society of Chemical Industry     

Synthesis and properties of novel polyamides containing sulfone‐ether linkages and xanthene cardo groups

In order to obtain polyamides with enhanced solubility and processability, as well as good mechanical and thermal properties, several novel polyamides containing sulfone‐ether linkages and xanthene cardo groups based on a new diamine monomer, 9,9‐bis[4‐(4‐aminophenoxy)phenyl]xanthene (BAPX), were investigated. The BAPX monomer was synthesized via a two‐step process consisting of an aromatic nucleophilic substitution reaction of readily available 4‐chloronitrobenzene with 9,9‐bis(4‐hydroxyphenyl)xanthene in the presence of potassium carbonate in N,N‐dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. Four novel aromatic polyamides containing sulfone‐ether linkages and xanthene cardo groups with inherent viscosities between 0.98 and 1.22 dL g^?1 were prepared by low‐temperature polycondensation of BAPX with 4,4′‐sulfonyldibenzoyl chloride, 4,4′‐[sulfonyl‐bis(4‐phenyleneoxy)]dibenzoyl chloride, 3,3′‐[sulfonyl‐bis(4‐phenyleneoxy)]dibenzoyl chloride and 4,4′‐[sulfonyl‐bis(2,6‐dimethyl‐1,4‐phenyleneoxy)]dibenzoyl chloride in N,N‐dimethylacetamide (DMAc) solution containing pyridine. All these new polyamides were amorphous and readily soluble in various polar solvents such as DMAc and N‐methylpyrrolidone. These polymers showed relatively high glass transition temperatures in the range 238–298 °C, almost no weight loss up to 450 °C in air or nitrogen atmosphere, decomposition temperatures at 10% weight loss ranging from 472 to 523 °C and 465 to 512 °C in nitrogen and air, respectively, and char yields at 800 °C in nitrogen higher than 50 wt%. Transparent, flexible and tough films of these polymers cast from DMAc solution exhibited tensile strengths ranging from 78 to 87 MPa, elongations at break from 9 to 13% and initial moduli from 1.7 to 2.2 GPa. Primary characterization of these novel polyamides shows that they might serve as new candidates for processable high‐performance polymeric materials. Copyright © 2010 Society of Chemical Industry     

Highly fluorinated poly(ether‐imide)s derived from 2,2′‐bis(3,4,5‐trifluorophenyl)‐4,4′‐diaminodiphenyl ether and aromatic dianhydrides

A new diamine, 2,2′‐bis(3,4,5‐trifluorophenyl)‐4,4′‐diaminodiphenyl ether (FPAPE) was synthesized through the Suzuki coupling reaction of 2,2′‐diiodo‐4,4′‐dinitrodiphenyl ether with 3,4,5‐trifluorophenylboronic acid to produce 2,2′‐bis(3,4,5‐trifluorophenyl)‐4,4′‐dinitrodiphenyl ether (FPNPE), followed by palladium‐catalyzed hydrazine reduction of FPNPE. FPAPE was then utilized to prepare a novel class of highly fluorinated all‐aromatic poly(ether‐imide)s. The chemical structure of the resulting polymers is well confirmed by infrared and nuclear magnetic resonance spectroscopic methods. Limiting viscosity numbers of the polymer solutions at 25 °C were measured through the extrapolation of the concentrations used to zero. M_n and M_w of these polymers were about 10 000 and 25 000 g mol^?1, respectively. The polymers showed a good film‐forming ability, and some characteristics of their thin films including color and flexibility were investigated qualitatively. An excellent solubility in polar organic solvents was observed. X‐ray diffraction measurements showed that the fluoro‐containing polymers have a nearly amorphous nature. The resulting polymers had T_g values higher than 340 °C and were thermally stable, with 10% weight loss temperatures being recorded above 550 °C. Based on the results obtained, FPAPE can be considered as a promising design to prepare the related high performance polymeric materials. Copyright © 2011 Society of Chemical Industry     

Synthesis and characterization of novel polyaspartimides derived from 2,2′‐dimethyl‐4,4′‐bis(4‐maleimidophenoxy)biphenyl and various diamines

A novel bismaleimide, 2,2′‐dimethyl‐4,4′‐bis(4‐maleimidophenoxy)biphenyl, containing noncoplanar 2,2′‐dimethylbiphenylene and flexible ether units in the polymer backbone was synthesized from 2,2′‐dimethyl‐4,4′‐bis(4‐aminophenoxy)biphenyl with maleic anhydride. The bismaleimide was reacted with 11 diamines using m‐cresol as a solvent and glacial acetic acid as a catalyst to produce novel polyaspartimides. Polymers were identified by elemental analysis and infrared spectroscopy, and characterized by solubility test, X‐ray diffraction, and thermal analysis (differential scanning calorimetry and thermogravimetric analysis). The inherent viscosities of the polymers varied from 0.22 to 0.48 dL g⁻¹ in concentration of 1.0 g dL⁻¹ of N,N‐dimethylformamide. All polymers are soluble in N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, dimethylsulfoxide, pyridine, m‐cresol, and tetrahydrofuran. The polymers, except PASI‐4, had moderate glass transition temperature in the range of 188°–226°C and good thermo‐oxidative stability, losing 10% mass in the range of 375°–426°C in air and 357°–415°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 279–286, 1999     

Aromatic polyamides with imide pendent groups

Aromatic polyamides with imide pendent groups were prepared from 4,4′-diaminodiphenylether and imide-diacid chlorides by solution polycondensation. Imidediacid chlorides used included the diacid chlorides of 5-maleimidoisophthalic, 5-dichloromaleimidoisophthalic, 5-tetrahydrophthalimidoisophthalic, 5-chlorendimidoisophthalic, 5-nadimidoisophthalic, 5-methylnadimidoisophthalic and 5-phthalimidoisophthalic acid. The pure aromatic polyamide from 4,4′-diaminodiphenylether and isophthaloyl chloride was also prepared for comparative reasons. Polyamide-imides are soluble in polar organic solvents and show good thermal resistance. They are film-forming and the films have good mechanical properties. Those polyamide-imides which contain unsaturated carbon-carbon bonds may be crosslinked by heating to 220°C, giving rise to insoluble materials with improved mechanical resistance.     

Benzoxazine monomers based on aromatic diamines and investigation of their polymerization by rheological and thermal methods

In the present article with the aim to find new polybenzoxazines with improved thermal properties, new benzoxazine monomers based on phenol and the following aromatic diamines were synthesized: 3,4′-oxydianiline (P-3,4′oda); o-tolidine (P-ot); m-tolidine (P-mt) and 4,4′-(1,3-phenylenedioxy)dianiline (P-tper) and their comparison with the previously known benzoxazines based on 4,4′-diaminodiphenylmethane (P-ddm); 4,4′-oxydianiline (P-4,4′-oda) and 2,2-Bis[4-(4-aminophenoxy)phenyl]propane (P-bapp). The dependence of the thermal and rheological characteristics on the structure of benzoxazine monomers based on various diamines was estimated and possible methods for their processing were identified. All the polybenzoxazines obtained in this work have high char yield and reduced flammability. It was found that the structure of the diamine can have a fundamental effect on both the rheological properties and heat resistance of polybenzoxazines. The benzoxazine monomers P-ddm, P-tper and P-4,4′oda retain viscosity up to 1 Pa s. at 110°C for 2 h, the P-tper monomer with a resorcinol bridge has about five times lower viscosity compared to the P-bapp monomer with a bisphenol A bridge. Polybenzoxazines based on the monomers P-ddm, P-mt, P-bapp and P-tper show excellent thermal stability with a temperature of 10% weight loss above 400°C. In particular, T_g of P-3,4′oda and P-mt monomers is relatively high (202 and 239°C, respectively), while P-ot's is unusually low (115°C), which may be caused by the specific effect of the substituents in the aromatic ring of the amine and their position.