Series Of Polyamides Research Articles

Synthesis and properties of novel aromatic polyamides derived from 2,2‐bis[4‐(4‐amino‐2‐fluorophenoxy) phenyl]hexafluoropropane and aromatic dicarboxylic acids

AbstractA series of polyamides were synthesized by the direct polycondensation of 2,2‐bis[4‐(4‐amino‐2‐fluorophenoxy)phenyl]hexafluoropropane with various commercially available dicarboxylic acids such as terephthalic acid, isophthalic acid, 5‐t‐butyl isophthalic acid, and 2,6‐naphthalene dicarboxylic acid. The synthesized polyamides were soluble in several organic solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and chloroform, and they exhibited inherent viscosities of 0.42–0.59 dL/g. The polyamides exhibited weight‐average molecular weights of up to 26,000, which depended on the exact repeating unit structure. These polyamides showed good thermal stability up to 440°C for a 10% weight loss in synthetic air. The polyamides synthesized from 5‐t‐butyl isophthalic acid and isophthalic acid exhibited glass‐transition temperatures of 217 and 185°C, respectively (by differential scanning calorimetry) in nitrogen. The polyamides synthesized from terephthalic acid and 2,6‐naphthalene dicarboxylic acid showed melting temperatures of 319 and 385°C, respectively. The polyamides films were pale yellow, with tensile strengths of up to 82 MPa, moduli of elasticity of up to 2.3 GPa, and elongations at break of up to 9%, which depended on the exact repeating unit structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 691–696, 2003

Azo-pendant polyamides which have the potential to photoalign chromonic lyotropic liquid crystals

A new series of polyamides (ph-azo-PAMs) was synthesized by the polycondensation of isophthalic acids having a photoisomerizable phenyl azo unit with 4,4′-diamino-3,5,3′,5′-tetraethyldiphenylmethane or by the esterification of poly(imino-5-oxyisophthaloylimino-1,4-(3,5-diethyl)phenylenemethylene-1,4-(3,5-diethyl)phenylene) with 4-(phenylazo)- or 4-(4′-substituted phenylazo)phenoxyalkanoic acid chlorides in the presence of triphenyl phosphate and pyridine in N-methylpyrrolidone. It has been confirmed that the spin-coated films of ph-azo-PAMs thus produced show reversible trans–cis photoisomerization of the azobenzene moieties. To examine the ability of the polymer films to act as command surfaces for a chromonic lyotropic liquid crystal (LLC), they were exposed to linearly polarized light and coated with aqueous LLC solutions of a chromonic dye compound. After drying the LLC solution, polarizing microscopic measurements were carried out to see whether the phototreated polymer films could bring about the in-plane anisotropic alignment of the dye molecule. The result was that 5h having an azo moiety with a dimethylamino substituent as a side group was among the most promising candidates.

Synthesis and characterization of polyamides and poly(amide–imide)s derived from 2,2-bis(4-aminophenoxy) benzonitrile

A series of polyamides and poly(amide–imide)s were prepared by the direct poly-condensation of 2,2-bis(4-aminophenoxy) benzonitrile [4-APBN] with aromatic dicarboxylic acids and bis(carboxyphthalimide)s in N-methyl-2-pyrrolidone [NMP] with triphenyl phosphite and pyridine as condensing agents. The synthesis of 4-APBN involves a nucleophilic displacement reaction in dipolar aprotic solvent with the alkali metal salt of p-aminophenol and an activated aromatic dichloro compound. Bis(carboxyphthalimide)s were prepared by condensation of 4,4 ′-diaminodiphenylsulfone, 3,3 ′-diaminodiphenylsulfone, 4,4 ′-diaminodiphenylether, 4,4 ′-diaminodiphenylmethane, 3,3 ′-diaminobenzophenone, and trimellitic anhydride at a 1:2 molar ratio. The inherent viscosities of the resulting polymers were found to be in the range of 0.31–0.93 dl/g and glass transition temperatures between 235 and 298 °C. All polymers were soluble in aprotic polar solvents such as dimethylsulfoxide and NMP. The results of thermogravimetry revealed that all the polymers showed no significant weight loss before 400 °C. Wide-angle X-ray diffractograms revealed that all polymers were found to be amorphous except for the polyamide derived from isophthalic acid and polyamide–imides derived from diaminodiphenylether and diaminobenzophenone based bis(carboxyphthalimide)s.

Preparation and characterization of a series of polyamides with long alkylene segments: Nylons 12 20, 10 20,s 20,6 20, 4 20 and 2 20

A series of nylons with long alkylene segments between amide groups were newly prepared by step-heating melt-polycondensation of 1,lS-octadecanedicarboxylic acid with various diamines. The prepared polyamides were characterized carefully. The results show that many properties of the prepared nylons change regularly with the length of methylene segments in diamines. In addition, nylon 2 20 has a relatively low molecular weight and much different melting and thermal decomposition behaviors in comparison with other nylons.

Rhodium(I) complex catalysts immobilized on polyamides having a pyridine moiety: Effect of the polymer structure

A series of polyamides have been synthesized by low-temperature interfacial condensation of 2,5- and 2,6-pyridinedicarboxylic chlorides and aliphatic diamines H 2N(CH 2) n NH, where n=2 and 6, and used as the model supports for immobilization of the Rh(I) complex catalyst. Physical characterization of these materials has involved the measurements of the structural parameters in the dry and swollen states by WAXS, SAXS, DSC, the nitrogen BET adsorption method, ISEC and pycnometry. From these results it can be concluded that the original polymer structure has been changed during the complex attachment giving rise to materials of higher porosity. The relation between the support structure and catalyst activity and selectivity was studied in the model reactions, namely, hydrosilylation of alkenes, dienes and alkynes. It was found that the catalyst activity decreased with increasing polymer crystallinity. A strong impact of support structure on the catalyst selectivity was also revealed. A high regioselectivity of the catalyst in the hydrosilylation of alkenes toward formation of the linear products was achieved due to the favorable microporous structure of the polyamide supports with pore sizes between 10 and 20 Å. It was also demonstrated that the stereoselectivity of the reaction can be reversed to the opposite direction by a proper choice of the donor functions in a polymer support, e.g. the traditional cis-selectivity of the rhodium (Rh) catalysts in the hydrosilylation of phenylacetylene was changed to trans-selectivity by use of the 2,5-py instead of 2,6-py moiety. The results of the 6–9 times repeated catalytic runs indicated high stability of the polyamide-supported catalysts.

Moisture transport properties of polyamides copolymers intended for food packaging applications

In this paper the barrier properties of a series of polyamides used for food packaging applications were analyzed. In particular, permeation of water through the investigated polyamides was studied and water diffusivity and solubility were evaluated as a function of water concentration. Water vapor sorption tests were performed at 25 °C and at several water vapor activities on the four samples investigated. The obtained values were related to the macromolecular chain modification deriving from the introduction of different comonomers.

Erosive wear behavior of various polyamides

A series of polyamides (PAs), namely, PA 6, PA 66, PA 66/610, PA 11, PA 12 and aromatic PA (brittle, hard and amorphous) was selected for investigating the effect of chemical structure and hence, mechanical properties on erosive wear behavior by impinging silica sand particles of 90–180 μm size at various angles and dozes. The results indicated that five polyamides including brittle PA showed maximum in wear versus impact angle relation at 30° confirming their ductile failure behavior. For two PAs, however, wear was maximum at 15°. Good correlation was observed in erosion rate and brittleness index of polyamides at incidence angles of 90 and 60°. Worn surface analysis was done using scanning electron microscopy to investigate wear mechanisms.

Synthesis and Characterization of New Organosoluble Polyamides and Polyimides Based on 2,2-Bis[4- (4-aminophenoxy)-3,5-dimethylphenyl]- hexafluoropropane

A new hexafluoro-containing diamine monomer, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]hexafluoropropane (TBAPHP), was synthesized in three steps, starting from hexafluoroacetone sesquihydrate and 2,6-xylenol. The monomer was reacted with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides to produce a series of polyamides and polyimides, respectively. The polyamides were prepared under Yamazaki reaction conditions. The polyimides were prepared by a two-stage procedure that included a ring-opening polyaddition yielding poly(amic acid)s, followed by a cyclodehydration to polyimides. The obtained polymers had inherent viscosities of 0.52–0.82 dL·g–1. All of the polymers dissolved in polar solvents, such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, and N,N-dimethylformamide. The polyimides derived from 4,4′-oxydiphthalic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride exhibited an excellent solubility and were dissolved in cyclohexanone, pyridine, tetrahydrofuran, and chloroform. These polymers showed glass transition temperatures of 231–301°C and decomposition temperatures at 10% weight loss ranging from 470 to 495°C in nitrogen and from 473 to 505°C in air. The tough and flexible polymer films obtained from solution casting showed tensile strengths of 78–96 MPa and tensile moduli of 2.0–2.4 GPa. Polymers containing methyl substituents had higher solubilities and Tg values than those without methyl substituents. In addition, the hexafluoroisopropylidene-containing polymers exhibited a higher solubility and thermal stability than those containing isopropylidene units. UV-visible absorption spectra revealed that the polyimides showed a better transparency than the polyamides.

Kinetic consequences of covalent linkage of DNA binding polyamides.

Polyamides composed of N-methylpyrrole (Py) and N-methylimidazole (Im) subunits can bind in the minor groove of DNA at predetermined sequences with subnanomolar affinity and high specificity. Covalent linkage of polymer subunits using a gamma-aminobutyric acid linker has been shown to increase both the affinity and specificity of polyamides. Using a fluorescence detected stopped-flow assay, we have studied the differences in association and dissociation kinetics of a series of polyamides representing unlinked, hairpin and cyclic analogues of the four ring polyamide ImPyPyPy-beta-Dp. Whereas the large differences seen in the equilibrium association constants between the unlinked and covalently linked polyamides are primarily due to higher association rate constants, discrimination between matched and mismatched sites by each polyamide can be ascribed in large part to differences in their dissociation rate constants. The consequences of this kinetic behavior for future design are discussed.

Polyamides based on diamines containing aryloxy groups: Structure-property relationships

Aromatic polyamides containing different numbers of p-oxyphenylene groups and different catenated positions in the benzene rings were prepared from terephthalic acid (TPA) and isophthalic acid (IPA) with various aryloxy-containing diamines by means of the phosphorylation polycondensation reaction. Most of the polyamides were moderately to highly crystalline, as indicated by X-ray diffraction and DSC measurements. Polyisophthalamides were readily soluble in polar amide-type solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). Some non-crystalline polyamides could afford tough films by solution casting. Most polyisophthalamides revealed discernible glass transition on their DSC curves, and their Tg values were recorded in the range of 215–238 °C. No discernible glass transitions were observed for the polyamides of TPA by DSC. The thermal stability of these polymers did not show clear dependence on the structure of the diacid or the diamine. In addition, a series of polyamides having pendant groups was synthesized from the polycondensation of TPA and IPA with 1,4-bis(4-aminophenoxy)benzene and its derivatives with methyl, tert-butyl, or phenyl substituent on the central benzene ring. In most cases, the incorporation of pendant groups generally resulted in an enhanced solubility and a decreased Tg and crystallinity.

Effects of Molecular Weight and Thermal Treatment on Wear Behavior of Polyamide 6

A series of polyamide 6 (PA 6) samples varying in their molecular weight (between 10000 and 50000) were annealed for 6 h in vacuum at various temperature (between 100 and 220°C) in order to create different morphological structures. The samples have been characterized with respect of their density, melting and crystallinity (from DSC), thermal expansion coefficient, humidity, predomination α- or γ-crystalline modification (from IR), shear melt viscosity and their tribological behaviour (the specific wear rate Ws ). It is found that density increases with increasing annealing temperature Ta but decrease with the rise of molecular weight (m.w.). The thermal expansion coefficient is more sensitive to Ta than to m.w. Contrary, shear-viscosity increases from 35 MPa for PA 6 with a m.w. of 10000 to 7200 MPa for samples with a m.w. of 50000. Concerning wear behavior it is concluded that the observed tendency for a decrease of Ws with an increase of Ta , particularly for samples with low m.w. is attributed to the formation of a more stable physical structure during annealed. This well defined tendency (except samples annealing at highest Ta ) is related to the observed drastic increase of shear melt viscosity with an increase of m.w.

Hydrosilylation of phenylacetylene catalyzed by metal complex catalysts supported on polyamides containing a pyridine moiety

The hydrosilylation of phenylacetylene with triethoxysilane catalyzed by polymer-supported Rh(I) and Pt(II) complexes has been investigated. Polyamides having the 2,5- and 2,6-pyridine moiety in their repeat units were used as the catalysts supports. The effect of the support structure, the type of solvent used, the substrate ratio and catalyst concentration on reaction selectivity were studied. X-ray photoelectron spectroscopy (XPS) was used to characterize the polymer supports and the supported catalysts before and after use. It was found that the selectivity of the hydrosilylation can be controlled by the chemical structure of the polymer support. When the reaction was catalyzed by Rh(I) attached to the polyamide with a pyridine substituted in the 2,6 position, β( Z)-vinylsilane was formed as the major product. Use of the same catalyst supported on the polymer with the 2,5-pyridine resulted in a reversal of the stereoselectivity and β( E)-vinylsilane was the major product. These results have been correlated with the reaction mechanism and the electron density on the rhodium centres. The binding energy for the Rh3d 5/2 attached to the 2,6-py moiety was found to be lower by 1.03 eV than that for the Rh supported on the 2,5-py type polymer. Hydrosilylation using Pt(II) as the catalyst supported on the same series of polyamides proceeded in the usual manner of cis addition to give predominantly β( E)-vinyl product and the α-isomer. The only difference caused by the presence of the polymer support was the increased yield of α-product. Recycling tests demonstrated high stability of the supported catalysts during prolonged use.

Synthesis and properties of ortho-linked polyamides based on a bis(ether-carboxylic acid) or a bis(ether amine) derived from 4- tert-butylcatechol

4- tert-Butyl-1,2-bis(4-carboxyphenoxy)benzene ( 2a) and 1,2-bis(4-aminophenoxy)-4- tert-butylbenzene ( 2b) were synthesized through the aromatic nucleophilic substitution reaction of 4- tert-butylcatechol with p-fluorobenzonitrile or p-chloronitrobenzene in the presence of potassium carbonate in N, N-dimethylformamide. Two series of polyamides with flexible main-chain ether linkages and ortho-phenylene units were prepared from dicarboxylic acid 2a with various aromatic diamines or from diamine 2b with various aromatic dicarboxylic acids via the phosphorylation reaction with triphenyl phosphite and pyridine. The inherent viscosities of these new polyamides were in the range of 0.52–2.60 dl g −1. Almost all the polyamides were noncrystalline and readily soluble in a variety of polar solvents and afforded transparent, flexible and tough films by solution casting. They have useful levels of thermal stability, associated with relatively high glass transition temperatures (most >200°C) and 10% weight loss temperatures in excess of 480°C in nitrogen or in air.

Synthesis and Properties of Polyamides and Polyesters On the basis of 2,2‘-Bipyridine-5,5‘-Dicarboxylic Acid and the Corresponding Polymer−Ruthenium Complexes

Two series of polyamides and polyesters derived from 2,2‘-bipyridine-5,5‘-dicarboxylic acid have been synthesized. Different types of aliphatic and aromatic diamine and diol monomers with different structure were polymerized with the diacid or diacid chloride by using different polymerization methods. Most of these polymers exhibited modest thermal stabilities with decomposition temperatures in the range 320−500 °C, depending on the structure of the polymer main chain. It was found that some polyamides with a rigid main chain formed a lyotropic mesophase when dissolved in concentrated sulfuric acid or HMPA−4% LiCl solvent systems. For those polyamides and polyesters with a more flexible main chain, a thermotropic liquid crystal phase was observed. If a long and flexible pendant chain was attached to the polyesters, side chain melting was observed before the onset of the crystalline−nematic transition. The 2,2‘-bipyridyl moieties were able to form a complex with ruthenium. These polymer−ruthenium complexes...

Partially aromatic polyamides based on tetraphenylthiophene diamine: Synthesis and characterization

Tetraphenylthiophene diamine (TPTDA) was prepared through a modified three-step route to achieve an improved overall yield. TPTDA reacted with succinic, adipic, suberic, sebasic, and fumaric acids via the Yamazaki phosphorylation method to yield novel partially aromatic polyamides (TPT series). A counterpart polyamide series based on p-phenylene diamine (Ph series) was also synthesized under the same conditions. All of the polymers were characterized by means of spectrochemical (Fourier transform infrared spectroscopy, 1H-nuclear magnetic resonance (NMR), and 13C-NMR) and thermal (differential scanning calorimetry and thermogravimetric) methods of analysis. Solubility of TPT polyamides was clearly improved due to the presence of the bulky aromatic diamine as well as flexible CH2—CH2 segments. The highly phenylated thiophene diamine moiety was recognized to improve thermal stability of the TPT polyamides in comparison with Ph polyamides (integral procedural decomposition temperature (IPDT) 480–517°C against 454–485°C). A favorable balance was recognized in regard to solubility, thermostability, and melting temperature in the TPT polyamides, especially TPT4 and TPT6. Therefore, they may be considered good candidates for processable polymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1144–1153, 2000

Synthesis and characterization of novel aromatic polyamides with polyalicyclic cardo groups

5,5-Bis[4-(4-carboxyphenoxy)phenyl]hexahydro-4,7-methanoindan (3a) and 5,5-bis[4-(4-aminophenoxy)phenyl]hexahydro-4,7-methanoindan (3b) were prepared in two main steps starting from the aromatic nucleophilic halogen-displacement of p-fluorobenzonitrile and p-chloronitrobenzene, respectively, with 5,5-bis(4-hydroxyphenyl)hexahydro-4,7-methanoindan in the presence of potassium carbonate in N,N-dimethylformamide (DMF). Using triphenyl phosphite and pyridine as condensing agents, two series of polyamides having polyalicyclic cardo units were directly polycondensated from dicarboxylic acid 3a with various aromatic diamines, or from diamine 3b with various aromatic dicarboxylic acids in the N-methyl-2-pyrrolidone (NMP) solution containing dissolved calcium chloride. High molecular weight polyamides with inherent viscosities between 0.73 and 1.44 dL/g were obtained. All polymers were readily soluble in polar aprotic solvents such as NMP and N,N-dimethylacetamide (DMAc) and afforded transparent, flexible, and tough films by solution casting. The glass-transition temperatures (Tg) of these aromatic polyamides were in the range of 219–253°C by DSC, and the 10% weight loss temperatures in nitrogen and air were above 467 and 465°C, respectively. A comparative study of some polyamides with an isomeric repeat unit is also presented. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4510–4520, 1999

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.

Preparation and characterization of new ferroelectric polymers

The odd polyamide series is shown to be a new class of ferroelectric polymeric materials based on the demonstration of the J-E and D-E hysteresis loops of the oriented and unoriented odd polyamide films. Both the remanent polarization (Pr) and coercive field (Ec) of the odd polyamides linearly increase with increasing amide content of the molecules. The ferroelectric response of the samples can be greatly enhanced by uniaxial drawing at room temperature.

Synthesis and properties of polyamides with [60]fullerene in the main chain

A novel series of polyamides having [60]fullerene moieties in the main chain were synthesized by a direct polycondensation of [60]fullerenobis(acetic acid) or [60]fullerenobis(acetic acid)/isophthalic acid mixture with a diamine in the presence of triphenyl phosphite and pyridine. Various properties of the polyamides were characterized by means of IR, GPC, TGA, DSC, UV–visible, and photoluminescence. The molecular weight Mw of the [60]fullerene-containing polyamides was observed in the range from about 300,000 to 3,000; upon the changing of the ratio of [60]fullerenobis(acetic acid)/isophthalic acid in the starting mixture, the resulting Mw decreased with increasing the ratio. Most of the thermal and optical properties gradually changed as the ratio changed; the major optical absorption band in visible range exhibited a significant tailing, which shifted toward a longer wavelength, while the photoluminescence spectrum red-shifted with increasing [60]fullerene content. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3139–3146, 1998

Synthesis and properties of polyamides with [60]fullerene in the main chain

A novel series of polyamides having [60]fullerene moieties in the main chain were synthesized by a direct polycondensation of [60]fullerenobis(acetic acid) or [60]fullerenobis(acetic acid)/isophthalic acid mixture with a diamine in the presence of triphenyl phosphite and pyridine. Various properties of the polyamides were characterized by means of IR, GPC, TGA, DSC, UV–visible, and photoluminescence. The molecular weight Mw of the [60]fullerene-containing polyamides was observed in the range from about 300,000 to 3,000; upon the changing of the ratio of [60]fullerenobis(acetic acid)/isophthalic acid in the starting mixture, the resulting Mw decreased with increasing the ratio. Most of the thermal and optical properties gradually changed as the ratio changed; the major optical absorption band in visible range exhibited a significant tailing, which shifted toward a longer wavelength, while the photoluminescence spectrum red-shifted with increasing [60]fullerene content. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3139–3146, 1998