Synthesis and properties of aromatic polyamides containing the cyclohexane structure

1,1-Bis[4-(4-carboxyphenoxy)phenyl]cyclohexane (III) and 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane (V) were prepared in two main steps starting from the aromatic nucleophilic substitution of p-fluorobenzonitrile and p-chloronitrobenzene, respectively, with 1,1-bis(4-hydroxyphenyl)cyclohexane in the presence of potassium carbonate in N,N-dimethylformamide (DMF). Using triphenyl phosphite and pyridine as condensing agents, two series of polyamides with cyclohexylidene cardo groups were directly polycondensated from dicarboxylic acid III with various aromatic diamines or from diamine V with various aromatic dicarboxylic acids in an N-methyl-2-pyrrolidone (NMP) solution containing dissolved calcium chloride. The polyamides exhibited inherent viscosities in the range of 0.45 to 1.78 dL/g. Almost all of the polymers were readily soluble in polar aprotic solvents such as NMP and N,N-dimethylacetamide (DMAc) and could afford transparent, flexible, and tough films by solution casting. The glass transition temperatures (T_g) of these aromatic polyamides were in the range of 180–243°C by DSC, and the 10% weight loss temperatures in nitrogen and air were all above 450°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3575–3583, 1999     

Thermal properties of wholly aromatic polyamides

Various wholly aromatic polyamides based on m-and p-phenylene diamines and isophthaloyl and terephthaloyl chloride have been synthesized and their thermal properties and oxygen index values have been studied. The effect of different substituents on the aromatic ring of the diamine have been explored by comparing their differential thermal analysis (DTA) and thermogravimetric analysis (TGA) behavior, their relative char yields at 700°C, and their oxygen indices. The ? Cl, ? NO₂, and ? OH substituted polyamides have been found to produce the highest char yields. The high char yields are probably associated with crosslinking occurring at high temperatures. Attempts at correlating char yield with oxygen index indicated enhancement for the chlorosubstituted aramids.     

Synthesis of aromatic polyamides having pyridine moiety and their lyotropic properties in solution

Fully aromatic polyamide containing pyridine moieties (PPy) were successfully synthesized either by interfacial or solution polycondensation to prepare polyamide with inherent viscosity as high as 4. Solution properties of PPy in sulfuric acid were investigated in terms of solution viscosity and lyotropic behavior. The polyamide had a better solubility in sulfuric acid than in poly(p-phenylene terephthalamide) (PT) and the PPy solution in sulfuric acid exhibited an optically anisotropic property in a wider range of concentrations at relatively low temperatures in comparison with the PT solution. Viscosities of the PPy solution and the film cast from the PPy solution indicated a phenomenon characteristic of a highly oriented rigid polymer molecule caused by a lyotropic behavior.     

Synthesis and properties of polyamides from 2,5-furandicarboxylic acid and aromatic and aliphatic diamines

Russian Chemical Bulletin - Polyamides based on the 5-hydroxymethylfurfural derivative (2,5-furandicarboxylic acid dichloroanhydride) and diamines of both aromatic and aliphatic series were...     

Synthesis and liquid crystal properties of mixed alkynyl-alkoxy-triphenylenes

The synthesis and liquid crystalline properties of some new multisubstituted triphenylenes are reported. The materials bear combinations of alkyne and alkoxy substituents and were designed to probe the structural factors controlling mesophase formation, type and stability in triphenylene discotics. A combination of factors contributes to mesophase stability in these systems. Compounds bearing two alkynes can support, and indeed enhance, columnar mesophase behaviour, but mesophase behaviour is completely suppressed when four or six alkynes are present. A twinned structure linked by a diacetylene bridge shows a stable nematic phase, but conversion to a saturated bridge destroys all mesophase behaviour.     

Synthesis and mesomorphic properties of trifluorobenzoate liquid crystal

Four series of trifluorobenzoate liquid crystals have been synthesized. Their phase transition temperatures have been also measured by texture observation in a polarizing microscope and confirmed by DSC. The influence of the lateral fluoro-substitution and triple bond has been also discussed.     

Crosslinked liquid crystal polymers from liquid crystal monomers: Synthesis and mechanical properties

Difunctional acrylates and methacrylate monomers have been made which are high order smectic liquid crystal (or crystalline) at room temperature. This report discusses materials with the following structure: F–S–M–S–F, where F is a functional group, acrylate or methacrylate (A or M); S is a spacer (CH₂)_n(n), and M is a mesogen—in this case 4,4′-dioxybiphenyl (B). They are codified as BnA or BnM where n is the number of methylenes in the spacer. High conversion with high T_g can be obtained when polymerizing in the smectic state because the reactive end groups are concentrated in a small volume and can react well with little or no diffusion. B2A, B3A, B6A, B11A, and B3M were polymerized in the smectic state and compared to polymers made at temperatures where the monomers were isotropic. High conversion was obtained below final T_g—even then, probably because the polymers were ordered. All the polymers were studied by WAXD and dynamic mechanical spectroscopy. Solid-state NMR on B3A showed that there was very high conversion of the double bonds at all temperatures. B3A photopolymerized in the smectic state (60–76°C) produced a crystalline polymer with T_g = 185°C (1 Hz). When photopolymerized at 85°C, above the isotropization temperature (T_i), a poorly organized polymer was obtained with a T_g of 155°C (1 Hz). Monomers with an odd number of methylene groups as spacers were crystalline after polymerization. With an even number of methylene groups, they lost most of their crystallinity on polymerization below T_i, but retained a low order smectic structure. Similar structures were obtained with all the monomers when they were polymerized above T_i. There was little effect of polymerization temperature on T_g when the spacers had an even number of methylene groups. © 1993 John Wiley & Sons, Inc.     

Thermal properties of some fully aromatic thermotropic liquid crystal polyesters

Wholly aromatic liquid crystalline main chain polyesters derived from terephthalic acid, phenyl- or (1-phenylethyl)hydroquinone modified with either 3,4′- or 4,4′-dicarboxydiphenylether and p-hydroxybenzoic acid, have been prepared by acidolysis and thermally investigated. All prepared polyesters exhibit excellent thermal stability up to about 400°C, however, the (1-phenylethyl)hydroquinone polyesters generally showed lower stability. Melting points could be decreased to around 200°C without any decrease in the thermal stability or the nematic range.     

Synthesis,photoluminescence, and electrochromic properties of wholly aromatic polyamides bearing naphthylamine chromophores

A series of novel polyamides with pendent naphthylamine units having inherent viscosities of 0.15–1.02 dL/g were prepared via direct phosphorylation polycondensation from various diamines and a naphthylamine‐based aromatic dicarboxylic acid, 1‐[N,N‐di(4‐carboxyphenyl)amino]naphthalene. These amorphous polyamides were readily soluble in various organic solvents and could be cast into transparent and tough films. The aromatic polyamides had useful levels of thermal stability associated with high glass‐transition temperatures (268–355 °C), 10% weight loss temperatures in excess of 480 °C, and char yields at 800 °C in nitrogen higher than 60%. These polymers showed maximum ultraviolet–visible absorption at 350–358 nm and exhibited fluorescence emission maxima around 435–458 nm in N‐methyl‐2‐pyrrolidinone solutions with fluorescence quantum yields ranging from 0.4 to 15.0%. The hole‐transporting and electrochromic properties were examined with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium tin oxide coated glass substrate exhibited one oxidative redox couple around 1.08–1.16 V (oxidation onset potential) versus Ag/AgCl in an acetonitrile solution and revealed good stability of the electrochromic characteristics, with a color change from colorless to green at applied potentials ranging from 0 to 1.6 V. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6094–6102, 2006     

Synthesis of hyperbranched aromatic polyamides by direct polycondensation

Some hyperbranched aromatic polyamides have been synthesized by direct polycondensation using the modified Higashi's method. Structures of the above polymers have been realized taking in proper account the analogies with amide group sequences of poly(p-phenyleneterephthalamide) (PPDT) and poly(p-benzamide) (PBA). Therefore, AB₂- type monomers as well as suitable combinations of different bi- and trifunctional reactants (AA + B₃) (e.g., p-phenylenediamine + trimesic acid or other trifunctional acids) have been considered. For the latter systems, network formation has been minimized. In the present paper, our results on their direct polyamidation together with some preliminary characterization data on the resultant hyperbranched aramids are given.     

Synthesis and characterization of some novel organometallic aromatic polyamides

Some novel ferrocene containing aromatic polyamides were prepared by low‐temperature solution phase polycondensation of 1,1′‐ferrocenedicarboxylic acid chloride with some newly synthesized aromatic diamines in tetrahydrofuran, in the presence of triethylamine. The amorphous polymers were derived in good yields, and did not melt at >350 °C. The monomers and the resulting polymers were characterized by their physical properties, elemental analysis, ¹H‐NMR, FTIR spectroscopy, differential scanning calorimetry and thermogravimetric analyses. The polymeric products were insoluble in common solvents tested. However, all were miscible in concentrated H₂SO₄, forming reddish brown solutions at ambient conditions. The glass transition temperatures (T_g) of these polymers were quite high, which is characteristic of aramids. They are stable up to 500 °C, with 10% mass loss observed in the range 400–650 °C. The activation energies of pyrolysis for each of the products were calculated by Horowitz and Metzger's method. Solution viscosities of the polymers were reduced in concentrated sulfuric acid, which is due to their non‐Newtonian behavior. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis and properties of aromatic polyamides derived from 1,6-bis(4-aminophenoxy)naphthalene and aromatic dicarboxylic acids

A new bis(phenoxy)naphthalene-containing diamine, 1,6-bis(4-aminophenoxy)naphthalene, was synthesized in two steps from the condensation of 1,6-dihydroxynaphthalene with p-chloronitrobenzene in the presence of potassium carbonate, giving 1,6-bis(4-nitrophenoxv)naphthalene, followed by hydrazine hydrate/Pd—C reduction. A series of polyamides were synthesized by the direct polycondensation of the diamine with various aromatic dicarboxylic acids in the N-methyl-2-pyrrolidone (NMP) solution containing dissolved metal salts such as CaCl₂ or LiBr using triphenyl phosphite and pyridine as condensing agents. The polymers were obtained in quantitative yield with inherent viscosities of 0.78–3.72 dL/g. Most of the polymers were soluble in aprotic solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), NMP, and they could be solution-cast into transparent, flexible and tough films. The casting films had tensile strength of 102–175 MPa, elongation at break of 8–42%, and tensile modulus of 2.4–3.8 GPa. The polymers derived from rigid dicarboxylic acids such as terephthalic acid and 4,4′-biphenyldicarboxylic acid exhibited some crystalline characteristics. The glass transition temperatures of the polyamides were in the range of 238–337°C, and their 10% weight loss temperatures were above 487°C in nitrogen and above 438°C in air. © 1995 John Wiley & Sons, Inc.     

Synthesis and properties of aromatic polyamides derived from 1,2-bis(4-aminophenoxy)benzene and aromatic dicarboxylic acids

1,2-Bis(4-aminophenoxy)benzene was synthesized in two steps by the preparation of 1,2-bis(4-itrophenoxy)benzene from 1,2-dihydroxybenzene (catechol) and p-chloronitrobenzene and subsequent reduction with a 10% Pd-C catalyst and hydrazine hydrate. Aromatic polyamides with an inherent viscosity in the range of 1.08–2.00 dL/g were prepared by the direct polycondensation of this diamine with various aromatic dicarboxylic acids in N-methyl-2-pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. Most of the polymers formed were soluble in aprotic solvents such as NMP and N,N-methylacetamide (DMAc), and afforded transparent, flexible, and tough films upon casting from DMAc solutions. Most of the cast films showed obvious yield points in their stress-strain curves and had tensile strength among 64–89 MPa, elongation at break among 5–23%, and initial modulus in 1.7–2.5 GPa. The glass transition temperatures (T_g) of these polymers were in the range of 207–278°C, and the 10% weight loss temperatures were recorded above 475°C in nitrogen and above 452°C in air. © 1995 John Wiley & Sons, Inc.     

Synthesis of thermotropic liquid crystal polyimide and its properties

Thermotropic liquid crystal polyimide which has neither an ester linkage nor a carbonate linkage was prepared by the polymerization of 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) and 1,3-bis[4-(4′-aminophenoxy)cumyl)]benzene (BACB). This polyimide shows the liquid crystal phase at 549-593 K. Mixing this liquid crystal polyimide or copolymerizing BACB decreases the melt viscosity of the thermoplastic polyimide (Aurum). © 1994 John Wiley & Sons, Inc.     

Synthesis of novel liquid crystal compounds with aromatic amide mesogenic cores

The synthesis and properties of a new series of compounds having aromatic amide mesogenic cores are reported. Most of these new compounds are thermotropic mesogens. In consideration of the fact that aromatic amides form crystals of high melting point which is unfavourable for the formation of thermotropic liquid crystals, we make use of lateral substitution to decrease both the packing efficiency and the hydrogen bonding, so that the melting temperature of the aromatic amides is sufficiently depressed. The lateral substituent used in these new compounds is bromine. In order to investigate the influence on properties of the end groups, different alkoxy, alkyl and other groups are used at the two ends of the rod-like molecules. The two ends are either identical or different, with an electron-donating alkoxy as one end and the electron-accepting cyano group as the other. The results indicate that appropriate lateral and terminal substitution is essential for the aromatic amides to form thermotropic liquid crystals. The peculiar mesophase characterized by an X-ray diffraction pattern of a SmC phase, but a texture of a nematic phase is also noted.     

Substituted rod-like aromatic polyamides: Synthesis and structure-property relations

The synthesis and structure-property relations of a number of novel substituted paralinked aromatic homopolyamides and copolyamides are described. The synthesis of the polyamides was carried out by polycondensation of activated N,N'-bis-(trimethylsilyl) substitued aromatic diamines and aromatic diacid chlorides. In order to improve the solubility and to lower melting temperatures, novel arylsubstituted terephthalic acids moieties, such as p-terphenyl-2,5-dicarboxylic acid and o-terphenyl-2,5-dicarboxylic acid, were used in combination with substituted and noncoplanar diamines. Depending on the chemical structure, polyamides with very high solubility (up to 40% w/w) in polar aprotic solvents such as N,N-dimethylacetamide without the addition of inorganic salts were obtained. Lyotropic liquid crystalline behavior was observed for the first time in polyamides which contain noncoplanar biphenylene units.     

Preparation and properties of fluorine-containing aromatic polyamides from tetrafluorophthaloyl chlorides and aromatic diamines

New fluorine-containing aromatic polyamides with inherent viscosities of 0.4–1.8 dL/g were prepared by the low temperature solution polycondensation of tetrafluoroisophthaloyl and tetrafluoroterephthaloyl chlorides with N,N′-bis(trimethylsilyl)-substituted aromatic diamines. The aromatic polyperfluoroisophthalamides were amorphous polymers with glass transition temperatures around 280°C, whereas the polyperfluoroterephthalamides were crystalline. Most of these aromatic polyamides were soluble in organic solvents, and began to decompose around 330°C in air or nitrogen atmosphere.     

Synthesis,characterization, and properties of semifluorinated organo‐soluble new aromatic polyamides

A series of organo‐soluble new polyamides were synthesized by the direct polycondensation of different semifluorinated aromatic diamines, namely 4,4‐bis[3'‐trifluoromethyl‐4'(4“‐amino benzoxy)benzyl]biphenyl; 4,4”‐bis(aminophenoxy)‐3'3“‐trifluoromethyl terphenyl; 1,3‐bis[3'‐trifluoromethyl‐4'(4”‐amino benzoxy)benzyl]benzene; 2,6‐bis(3'‐trifluoromethyl‐p‐aminobiphenyl ether)pyridine; and 2,5‐bis(3'‐trifluoromethyl‐p‐aminobiphenyl ether)thiophene with 5‐t‐butyl‐isophthalic acid. The polymers were fully characterized by elemental analysis and IR, NMR spectroscopies. The synthesized polyamides were soluble in several organic solvents such as 1‐methyl‐2‐pyrrolidone, N,N‐dimethylformamide, N,N‐dimethylacetamide, tetrahydrofuran, and dimethyl sulfoxide at room temperature. They showed inherent viscosities of 0.42–0.63 dl/g. The polyamides exhibited weight‐average molecular weights of up to 233,000, which depended on the exact repeating unit structure. The polyamides synthesized from 4,4‐bis[3'‐trifluoromethyl‐4'(4”‐amino benzoxy)benzyl]biphenyl and 5‐t‐butyl isophthalic acid exhibited highest glass‐transition temperatures 261°C (evaluated by differential scanning calorimetry) in nitrogen. These polyamides showed good thermal stability up to 475°C for a 10% weight loss in air. The polyamides films were clear and flexible in nature with tensile strengths of up to 88 MPa, modulus of elasticity of up to 1.81 GPa, and elongations at break of up to 25%, which depended on the exact repeating unit structure. X‐ray diffraction measurements indicated that these polyamides were amorphous in nature. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and properties of aromatic polyamides derived from 1,7-bis(4-aminophenoxy)naphthalene and various aromatic dicarboxylic acids

A series of novel bis(phenoxy)naphthalene-containing polyamides having inherent viscosity up to 2.02 dL/g were synthesized by the direct polycondensation of the diamine 1,7-bis(4-aminophenoxy)naphthalene with various aromatic dicarboxylic acids in N-methyl-2-pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. Most of the polyamides could be readily dissolved in polar aprotic solvents such as N,N-dimethylacetamide and NMP, and could be solution-cast into transparent, flexible, and tough films. These polymers had glass transition temperatures in the range of 139–263°C, and 10% weight loss temperatures in nitrogen and air were above 499 and 484°C, respectively. © 1996 John Wiley & Sons, Inc.