芳香-脂肪族共聚酰胺溶致液晶行为的研究

本文对脂肪族二元胺(ADA、NH_2(CH_2)_nNH_2、n=2、6、8、10、12),对苯二胺(PPD)和对苯二甲酰氯(TPC)三元芳香-脂肪族共聚酰胺硫酸溶液的溶致液晶性能进行了研究.利用偏光显微镜、小角和宽角X-光衍射确定了该类共聚酰胺溶致液晶中介相的类型随共聚物中脂肪族二胺链单元含量的变化规律.     

芳香─脂肪族共聚酰胺的序列结构和溶致液晶性能

本文利用对苯二甲酰氯（ＴＰＣ），对苯二胺（ＰＰＤ）和亚甲基数为２和６的两种脂肪族二无胺（ＡＤＡ）合成了具有不同序列结构的芳香－脂肪族共聚酰胺。研究了共了聚酰胺的序列结构参数－无规度Ｂ和数均序列长度Ｌｎ与液晶临界浓度Ｃ＊和中介相的类型之间的关系。     

芳香─脂肪族共聚酰胺的序列结构和溶致液晶性能

本文利用对苯二甲酰氯（ＴＰＣ），对苯二胺（ＰＰＤ）和亚甲基数为２和６的两种脂肪族二元胺（ＡＤＡ）合成了具有不同序列结构的芳香一脂肪族共聚酰胺．研究了共聚酰胺的序列结构参数──无规度Ｂ和数均序列长度Ｌｎ与液晶临界浓度Ｃ＊和中介相的类型之间的关系．     

ODD-EVEN EFFECT OF LYOTROPIC LIQUID CRYSTALLINE PROPERTIES OF AROMATIC-ALIPHATIC COPOLYAMIDES

 A series of aromatic-aliphatic copolyamides containing different aliphatic diamine units was synthesized by low temperature solution polycondensation. The liquid crystalline critical concentration (c^*) and liquid crystalline critical temperature (T^*) of these copolyamides exhibited an odd-even zigzag effect with the odd-even variation of carbon atom number in the aliphatic dimes used.     

N-Alkyl-substituted polyamides and copolyamides having long methylene chain units

N-Alkyl-substituted polyamides and copolyamides have been prepared from N,N′-dialkyl p-xylenediamine and N,N′-dialkyl hexamethylenediamine with long-chain aliphatic dicarboxylic acids. Crystalline N-alkyl polyamides were obtained by the use of dicarboxylic acids higher than C₁₆. The melting point versus composition curves for the crystalline N-alkyl copolyamides which were prepared from a mixture of diamine and the corresponding N-alkyl diamine with α,ω-octadecanedioic acid showed convex type plots. X-ray examination of N-alkyl copolyamides revealed that all the systems behaved in the same basic manner, the second component was always present without dissolving in the lattice of the first. Dilatometric curves showed two inflection points, corresponding to the melting points of the N-alkyl and unsubstituted polyamides respectively. From these results, a block copolymer structure was suggested for the N-alkyl copolyamides. The mechanisms for the formation of the block structure were also discussed.     

Comparative analysis of structure and temperature behaviour of two copolyamides - regular KEVLAR and statistical ARMOS

In the present investigation X-ray diffraction techniques, DSC and dynamic mechanical relaxation (DMR) methods have been employed to compare the structure and thermal behaviour of Kevlar (“DuPont”, USA) and Armos (Russia) fibers. Our recent studies have indicated that the non-crystalline phase of copolyesters always contains LC smectic structure in addition to some part of the nematic LC mesophase. It turned out that the copolyamides also possess this interesting feature. Moreover, on heating of a semicrystalline copolyester always the second order phase transition from the crystalline state to condis mesophase has been observed, whereas in the case of copolyamides such a transition has the «virtual» character. As was established by other authors both polymers under study reveal the moisture content. The changes in wide angle X-ray scattering of copolyamides under heat treatment were interpreted in terms of desorption of bound water and structural rearrangement in the plane perpendicular to the chain axis involving of the hydrogen bonding between neighboring macromolecules.     

Isomorphism in copolyamides of long repeating chain units containing oxa- and thia-alkylene linkages

Various copolyamides of long repeating chain units were prepared from hexamethylenediamine (HMDA) and p-xylylenediamine (PXDA) with aliphatic dicarboxylic acids of three structural types: α,ω-alkanedioic, α,ω-oxaalkanedioic, and α,ω-thiaalkanedioic acids. Both binary and ternary combinations of these dicarboxylic acids having the same number of chain atoms with the diamine afforded highly crystalline copolyamides. In all cases of these copolymers, the plots of the melting points versus the compositions are expressed by linear relations, even in the ternary systems. For example, the melting points of the copolyamides of HMDA with 6-oxaundecanedioic and 6-thiaundecanedioic acids are practically unchanged in all ranges of composition. The same relation is also observed in the corresponding copolyamides of PXDA. The relation between the densities and the composition is plotted with good linearity in every case. From x-ray examination, the lattice spacings of each copolyamide are ascertained to be unchanged by the composition. These results reveal that methylene, ether, and thioether linkages are in the relation of isomorphous replacements for each other in these copolyamide systems. Moreover, the linear relationship between the melting point and the composition is explained by assuming that the entropy of fusion in these copolyamides changes linearly according to the change of the composition.     

Copolyamides of nylon-4,6 and nylon-4,T

Copolyamides of nylon-4,6 and nylon-4,T were prepared by a two-step method: (1) a prepolymerization in an autoclave (40 min at 210°C) and (2) a postcondensation in the solid state (4 h, 260°C). On these materials was studied the melting behavior with DSC, the crystalline structure with WAXS, the water absorption, and the mechanical properties with a torsion pendulum. In these copolyamides the order was found to remain high, but the crystalline structures of -4,6 and -4,T were not isomorphous. The torsion moduli increased with -4,T content both at RT and at 140°C.     

Aromatic Polyamides of 2,6-Naphthalenedicarboxylic Acid

Wholly aromatic polyamides have been prepared by the interfacial polycondensation of 2,6-naphthalenedicarboxylic acid chloride with m-phenylenediamine. Also, copolyamides with isophthaloyl or terephthaloyl chlorides and the naphthalene diacid chloride were synthesized. The resultant polyamides were amorphous or slightly crystalline as determined by x-ray diffraction, had tensile properties characteristic of hard, strong materials, and were more thermally stable than aromatic polyamides prepared solely from benzene diacid chlorides.     

Thermal properties of poly-ε-caprolactam and copolyamides based on ε-caprolactam

The copolyamides consisting of ε-caprolactam and 6.1–24.5 wt.% of nylon salt prepared from adipic acid and 1-(2-aminoethyl) piperazine were synthesized. Physical and thermal characteristics of polyamide 6 and the copolyamides were compared. Nylon salt does not influence the polyreaction equilibrium so it is possible to prepare the copolyamides with high molecular weight and with the content of low-molecular compounds comparable with that of pure PA 6. Melting temperatures of the copolyamides are lower in comparison with PA 6 and decrease proportionally to the amount of the nylon salt. The thermal stability of the copolyamides is good and equal to that of PA 6. The melting enthalpies indicate that the process of crystallization of the copolyamides is influenced by the time of crystallization and the amount of comonomer present. Longer time of the crystallization assures higher degree of crystallization. The kinetics and the level of crystallization are positively influenced by the mobility of copolyamide segments mainly up to 10 wt.% of comonomer.     

Optically active copolyamides by melt and solution condensation polymerization

The melt and solution condensation copolymerization of nylon salts which were prepared from d-camphoric acid and adipic acid with hexamethylenediamine were carried out, and optically active copolyamides were obtained. The copolyamides obtained had a positive specific rotation. The specific rotations for the copolyamides increased with increasing content of d-camphoryl units in the copolymers. The optical rotatory dispersion of the copolyamides had positive curves and were found to fit the simple Drude equation. The λ_c values of the polymers obtained by the melt and solution condensation polymerization were 241 mμ and 245 mμ, respectively.     

Anionic copolymers of caprolactam with laurolactam (nylon 6/12 copolymers)—I. Preparation and general properties

Copolyamides of high mol.wt were obtained by the anionic copolymerisation of ?-caprolactam with ω-laurolactam at 180°C, using a sodium caprolactamate-N-phenylcarbamoylcaprolactam initiator activator system. The proportions of co-units in the copolymers were close to those in the comonomer feeds. The copolymers were crystalline and substantially fully hydrogen-bonded over the whole range of compositions, except at 50/50 mole% ratio, each displayed only one crystalline phase corresponding to that of the major component. T_m and density measurements indicated a crystallinity minimum at 50 60 mole% NH(CH₂)₅CO unit content. The properties of the copolyamides were consistent with random copolymeric structures.     

Sequence distribution of repeating units of copolyamides by interfacial or solution methods

The sequence distribution of repeating units of copolyamides from different diamines with isophthaloyl or terephthaloyl chlorides and dithiophenyl adipate have been investigated either by interfacial or solution methods to aim at the sequence control of the copolyamides by solvents. Copolycondensation of dithiophenyl adipate and isophthaloyl chloride with m-xylylenediamine in various solvents yielded copolyamides having different compositions of repeating units. Aprotic polar solvents produced random copolyamides having the same compositions as feed ratios of the comonomers, while nonpolar solvents yielded copolyamides rich in isophthaloyl units. Also the sequence distribution of the copolyamides from m- and p-phenylenediamines with isophthaloyl chloride was affected by solvents; nonpolar solvents produced copolyamides having a less-random and block character of the repeating units either by interfacial or solution methods.     

Synthesis and characterization of glycine copolymers of nylons 6 and 12

Copolymers of glycine and 6-aminohexanoic or 12-aminododecanoic acid within a range of molar compositions from 80/20 to 5/95 were prepared by solution polycondensation of the adequate proportion of the respective pentachlorophenyl ester hydrobromides. Despite their random composition, the copolymers obtained were found to be highly crystalline. Intrinsic viscosities of 2/6 and 2/12 copolyamides were similar and rather low (M_n, ca. 3000-5000). Thermal post-polycondensation allowed to increase the molecular weight of 2/12 copolyamides, so that fibers could be prepared. The composition and sequence distributions were evaluated by means of ¹H- and ¹³C-NMR spectroscopies. Copolyamides were also characterized in terms of thermal properties. Melting and glass transition temperatures are reported. Crystallinity was evaluated from heats of fusion. Crystalline structure was examined by infrared spectroscopy and wide-angle x-ray diffraction. The presence of structures related to the polyglycine I and to α/γ-nylons was confirmed depending on the molar composition. Highly oriented fibers with good tensile properties were obtained from the nylon 2/12 (10 : 90) copolymer. © 1995 John Wiley & Sons, Inc.     

Syntheses and properties of phosphorus-containing copolyamides

Caprolactam was copolymerized with 1,5-dioxo-1-methyl-4-azaphosphepane or methylphosphacaprolactam. The molecular weight of the resulting copolymers decreased with increasing concentration of the thermally labile phosphorus moieties. Copolymers based on ≥40% caprolactam were shown to be crystalline by differential scanning calorimetry and x-ray techniques. As the concentration of the phosphorus structures in the copolymers increased, the glass transition and crystallization temperatures increased while the melting temperatures, crystallinities, and thermal stabilities decreased. Melt blends of nylon 6 and polymethylphosphacaprolactam were shown by differential scanning calorimetry, a selective extraction technique, and elemental analysis to contain appreciable amounts of block copolyamides, and no crystalline random structures were detected. The thermal stabilities of the melt blends were similar to those of random copolymers having comparable concentrations of the phosphorus-containing sequences.     

Preparation and properties of aromatic copolyamides from aromatic diisocyanates and aromatic dicarboxylic acids

Wholly aromatic random copolyamides of high molecular weights were prepared by the high-temperature solution polycondensation of an aromatic diisocyanate, 4,4′-methylenedi(phenyl isocyanate) or 2,4-tolylene diisocyanate, with a mixture of isophthalic acid and 4,4′-oxydibenzoic acid. Glass transition temperatures of the polyamides and copolyamides were between 229 and 273°C; this depended on the combination of diisocyanates and dicarboxylic acids used. These aromatic copolyamides showed better solubility in various organic solvents and reduced crystallinity, compared to the corresponding homopolyamides. The copolyamides prepared from 2,4-tolylene diisocyanate had greater solubility and higher glass transition temperatures than those obtained from 4,4′-methylenedi(phenyl isocyanate).     

Quick analysis of composition of semi-aromatic copolyamide via 13C NMR study

Standard high resolution ¹³C NMR spectra of PA10T, PA6T, PA106, and PA66 were obtained by a nonacidic solvent mixture of HFIP and CDCl₃. Several chemical shifts were found extremely sensitive to the polyamide type. According to the standard spectra, semi-aromatic copolyamides comprising PA10T, PA6T, PA106, and PA66 units could be distinguished. The ratio of each polyamide component in the copolyamide was determined through the integration of the methylene carbon peak associated with the amine group. ¹³C NMR analysis results were consistent with the theoretical values and copolyamide hydrolysis test results, making ¹³C NMR analysis quite reliable on the quick composition analysis of semi-aromatic copolyamides. Based on this technique, several commercial semi-aromatic copolyamides were further examined and their compositions were easily determined.     

Konstitutionsisomerie in Polykondensaten. Teil VI. Synthese und Eigenschaften von völlig geordneten und ungeordneten Bipolyamiden aus cis-2,6-Dimethylpiperazin und 1,2,5-Thiadiazol-3,4-dicarbonyl-dichlorid

Constitutional Isomerism in Polycondensates. Synthesis and Properties of Perfectly Regular and Random Bipolyamides from cis-2,6-Dimethylpiperazine and 1,2,5-Thiadiazole-3,4-dicarbonyl Dichloride The synthesis of constitutionally perfectly regular and random alternating copolyamides from the ‘symmetric’ monomer 1,2,5-thiadiazol-3,4-dicarbonyl dichloride ( 4 ) and the ‘non-symmetric’ monomer cis-2,6-dimethylpiper-azine ( 7 ) by solution and interfacial polycondensation methods is described. Their constitutional regularities (s values) were determined by high-resolution ¹³C-NMR spectroscopy in CDCl₃ solutions. Ordered and random copolyamides were amorphous with T_g values of ca. 200°. However, the regular head/tail and the random copolyamides with low molecular weights could be partially crystallized by annealing and showed large differences in their melting points (54°). Beside other physical properties, the membrane properties of the copolyamides were carefully investigated. In H₂O desalination by reverse osmosis, no differences in salt rejections and permeabilities between constitutionally regular and random copolyamides were found (within experimental errors). In contrast, the regular head/head/tail/tail- and head/tail-type copolyamides showed considerably larger separation factors in the gas separation (methane/hydrogen) than the random ones.     

Structure-property relations and processing of rod-like aromatic polyamides

Homopolyamides and copolyamides with structural characteristics such as bulky lateral substituents, non-coplanar, 2, 2′-dimethylbiphenylene units and comonomers of different length were prepared and their structure-property relations investigated. Polyamides with high solubilities and very low or no degree of crystallinity are obtainable by a combination of monomers with bulky lateral substituents and non-coplanar biphenylene units. These polyamides form tough, transparent films with good mechanical and thermal properties. Lyotropic liquid crystalline behavior was found in some cases for polyamides with non-coplanar biphenylene units. The incorporation of monomers with bulky substituents on the terephthalic acid unit lowers the chain stiffness and significantly influences the formation of lyotropic solutions.     

Gas permeability and selectivity of hexafluoroisopropylidene aromatic isophthalic copolyamides

The synthesis, thermal, and gas transport properties of poly(hexafluoroisopropylidene isophthalamide), HFA/ISO homopolymer, and HFA/TERT‐co‐HFA/ISO copolyamides with different poly(hexafluoroisopropilydene‐5‐t‐butylisophthalamide), HFA/TERT, ratios are reported. The results indicate that the glass transition temperatures of the copolyamides increase as the concentration of HFA/TERT in the polyamide increases. The gas permeability coefficients in the polyamides and copolyamides are independent of pressure or decrease slightly particularly with CO₂, N₂, and CH₄. It was seen that HFA/TERT is 2–6 times more permeable than HFA/ISO, depending on the gas being considered. This was assigned to the presence of the bulky lateral substituent, t‐butyl group in HFA/TERT and HFA/TERT‐co‐HFA/ISO copolyamides. This substituent increases fractional free‐volume, as expected. Therefore, the gas permeability and diffusion coefficients generally increase with increasing fractional free‐volume. The experimental results for the gas permeability and permselectivity for the copolyamides was well represented by a logarithmic mixing rule of the homopolyamides permeability coefficients and their volume fraction. The selectivity of gas pairs, such as O₂/N₂, CO₂/CH₄, and N₂/CH₄ decreased slightly with the addition of HFA/TERT. The temperature dependence of permeability for homopolyamides and copolyamides can be described by an Arrhenius type equation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2625–2638, 2005