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  • Chemistry  (45)
  • crystal structure of poly(p-benz-amide)  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Nematogenic block copolymers of rigid and flexible aromatic units. I. Synthesis and characterization (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 653-667 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three types of wholly aromatic block copolymers were synthesized using the phosphorylation reactions of Yamazaki and Higashi. Each copolymer contained blocks of rigid and flexible units. The first copolymer, PBA/PABH-T, contains blocks of poly(p-benzamide) and the polyterephthalamide of p-aminobenzhydrazide. The second copolymer, PBA/MPD-I, contains blocks of poly(p-benzamide) and poly(p-phenylene isophthalamide), whereas the third, PPD T/MPD-I, contains blocks of poly(p-phenylene terephthalamide) and poly(m-phenylene isophthalamide). Three synthetic routes were used for the preparation of the block copolymers. In the two-step polycondensation (A), monomers of the flexible block are added to the rigid prepolymer. The multistep method (B) differs in that the rigid prepolymer is carboxy-terminated prior to addition of the monomers of the flexible block. Carboxy-terminated prepolymer of the rigid block is reacted with amine-terminated prepolymer of the flexible block in the two-pot condensation (C). The presence of a considerable amount of the flexible homopolymer is indicated by viscosity, extraction, and NMR studies, particularly when methods A and C were used. The flexible homopolymer can be extracted by using a nonsolvent for the rigid blocks. Extraction of the rigid homopolymer (which may also be presumed to be produced) entails a more elaborate procedure. In principle, one can use these methods to obtain pure block copolymer for study of mixtures with the rigid and flexible homopolymers. Phase studies of some of these systems will be reported in a following paper.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080250217
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Nematogenic block copolymers of rigid and flexible aromatic units. IV. Synthesis by two-pot phosphorylation reactions (1989)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 27 (1989), S. 59-63 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1989.140270203
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Aromatic rigid chain copolymers. I. Synthesis, structure, and solubility of phenyl-substituted para-linked aromatic random copolyamides (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 1175-1195 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four 2,5-biphenylene based difunctional condensation monomers, such as 2,5-diphenyldicar-boxylic acid or phenylterephthalic acid (PTA), 2,5-bis(carbonylimino-4-benzoic acid)biphenyl (2,5-BCIBABP), 2,5-diaminobiphenyl hydrochloride (2,5-DABP.HCl) and 2,5-bis(iminocarbonyl-4-benzoic acid)biphenyl (2,5-BICBABP), have been synthesized and characterized. These monomers were polymerized in combination with terephthalic acid (TA) and p-phenylenediamine (PPD) via the phosphorylation reaction to prepare a series of phenyl-substituted random copolyamides having all amide groups attached to para-positions of the benzene rings. All the copolyamides have been characterized by solubility, solution viscosity, and by differential scanning calorimetry (DSC). Some of these copolyamides have unusual solubility in organic solvents such as N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidinone (NMP) containing dissolved lithium chloride. A few copolyamides were tested for lyotropic behavior and found to form anisotropic solutions at critical concentrations in organic solvents. A randomly distributed unsymmetrical phenyl substituent on the benzene ring of para-oriented wholly aromatic polyamides dramatically changes the solubility and melting point. The phenyl substituent on a terephthalic acid unit is more efficient in decreasing melting point and increasing solubility in organic solvents of aromatic polyamides than the one on a p-phenylenediamine unit. However, the former also introduces a more flexible link in the extended polyamide chain.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080270407
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  • 4
    Electronic Resource
    Electronic Resource
    Mesogenic random copolymers. II. Copolymers with one flexible and two rigid segments (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 19-30 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have investigated copolyesters based on a single aliphatic dibasic acid flexible segment and two rigid segments arising from 4,4′-dihydroxybiphenyl (PB) and 2,6-dihydroxynaphthalene (PN). Homopolyesters based on the latter rigid segment exhibit no enantiotropic mesophase for 5 ≤ n ≤ 8. The copolymers are designated PBN-n where n is the number of methylene units in the dibasic acid. From the temperature-composition phase diagram, the odd-membered PBN-5 and PBN-7 exhibit only a nematic phase. The temperature range of the nematic phase decreases progressively with increasing mole fraction of naphthalene units. The even-membered PBN-6 and PBN-8 exhibit a smectic SH mesophase and a newly induced nematic phase. Comparison with a previous study of copolymers involving a single rigid segment and two flexible segments reveals that the smectic SH phase is more easily disrupted, and converted to a less ordered nematic phase, by different rigid segments than by different flexible segments. The isotropization entropy of a series of nematogenic equimolar copolymers exhibits a marked odd-even effect, with the observed ΔSNI values being quite large for the even-membered copolymers.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090250102
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  • 5
    Electronic Resource
    Electronic Resource
    Fiber spinning from the nematic melt. IV. Effect of P oxybenzoate crystallinity on the spinning and fiber properties of the copolyester of polyethylene terephthalate and p-oxybenzoate (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 2303-2314 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have previously reported two studies of the rheology and fiber properties of one sample of the copolymer of polyethylene terephthalate having 60 mol% of p-oxybenzoate (PHB) units. The DSC curve of that sample exhibited crystalline melting transitions, and the sample appeared to contain PHB blocks. Here we compare those results with observations for a second sample that, although nominally the same polymer, appears to be more random because it exhibits little PHB crystallinity. We had previously reported that the flow of the copolymer containing PHB blocks was non-Newtonian at all temperatures, and that it exhibited a thermal history effect. We find the flow of the more random polymer is Newtonian above the melting temperature, and the melt viscosity of the more random copolymer exhibits no thermal history effect. Fibers were spun from the more random copolymer with a capillary rheometer using a capillary having a length/diameter ratio of 14.1 and a shear rate at the wall of 6.4 sec-1. Spinning temperatures were 250, 260, and 280°C, and the spin draw ratio was examined as a variable. The initial modulus increased with spin draw ratio but exhibited no dependence upon the spinning temperature. For the copolymer containing PHB blocks, the initial modulus increased as the spinning temperature was raised. These differences are due to the larger amount of PHB crystallinity in the more blocky sample. When chips of the more random sample were heated for 1 h at 235°C, the melt viscosity increased and the initial modulus of the fibers decreased. These changes are due to the crystallization of longer PHB blocks produced by melt interchange.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090251108
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  • 6
    Electronic Resource
    Electronic Resource
    Fiber spinning from the nematic melt. VI. Flow instabilities in the 30:70 copolyester of hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 1837-1851 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rheological behavior and fiber spinning are investigated for the Celanese liquid crystal copolyester 30 mol% p-hydroxybenzoic acid and 70 mol% 2-hydroxy-6-naphthoic acid (designated as 30HBA/70HNA) with inherent viscosity 7.8 dL/g. Shear thinning viscosity, and yield stress are observed at low shear stress, which probably results from the existence of crystallites in the melt.The crystal-nematic melting point of the copolymer, as measured by differential scanning calorimetry, is around 309°C. Extrudates are collected at four different temperatures ranging from 315 to 345°C. Melt fracture and die swell are observed above 335°C at low shear stress. A wide-angle x-ray diffraction (WAXS) study of an annealed sample indicates that the abnormal phenomenon may be due to crystallites arising from blocky units of HNA. Fiber spinning is performed at high shear rate at 325 and 335°C. Flow is stable under these conditions. The spin draw ratio is the ratio of take-up velocity to the velocity of extrudate existing from the capillary. The initial modulus reaches a maximum at a fairly low spin draw ratio. Instron and wide-angle x-ray (WAXS) studies show that the mechanical properties and orientation are poor for the fiber spun near the crystal-nematic melting point. Also, thermal history is found to affect the rheological behavior. Heat treatment offibers, particularly those which are well oriented, brings an improvement of mechanical properties.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1989.090270905
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  • 7
    Electronic Resource
    Electronic Resource
    Poly(p-benzamide): Magnetic field orientation, solvation, and crystal-crystal transformations (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 1115-1119 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The morphological features of poly(p-benzamide) films cast in a magnetic field from solutions in N,N-dimethylacetamide containing LiCl are reported. Three crystal modifications are found, one solvated and the other two containing no solvent. The solvated crystal grown in a magnetic field is oriented with the molecules parallel to the field. It transforms to an oriented amorphous phase by loss of solvent, and this conversion is accelerated by the presence of moisture. Upon annealing at an elevated temperature, the crystalline solvate transforms to a second crystal form, while the amorphous sample is converted to a third crystalline modification. All three crystalline forms have almost the same fiber identity period, which corresponds to a nearly fully extended chain conformation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1986.090240512
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  • 8
    Electronic Resource
    Electronic Resource
    Films solidified from a lyotropic mesophase which retain the cholesteric structure (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 173-184 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solidified cholesteric films of α-helical poly(γ-methyl L-glutamate) and poly(γ-benzyl L-glutamate) were prepared by casting from solutions of the lyotropic cholesteric mesophase. Colored films can be prepared in this manner, so the cholesteric structure is retained with a pitch corresponding to a visible wavelength. Their iridescent colors can cover the full range of the visible spectrum, and the colors remain unchanged for years. Although the films are similar in optical properties to those of fluid cholesteric phases, the temperature dependence of the color is quite different. On stretching, the film undergoes a permanent deformation, and the iridescent color is shifted toward the blue. If t0 is the initial film thickness and Δt is the change in thickness after stretching the film, the relative change in pitch, -ΔP/P0, of the cholesteric structure increases linearly with -Δt/t0 in the range -Δt/t0 〉 0.10. This reduction of the pitch is attributed to a decrease in the number of pseudonematic layers in the span of one pitch, which may be interpreted in terms of delamination using an angle-ply model of the cholesteric structure.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090250113
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  • 9
    Electronic Resource
    Electronic Resource
    Thermotropic polyesters of 4'-hydroxyphenyl-4-hydroxybenzoate: A study of the transition temperatures (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 1173-1186 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyesters based on 4'-hydroxyphenyl-4-hydroxybenzoate and dichlorides of dibasic acids, prepared using a high-temperature solution polycondensation in 1-chloronaphthalene, exhibit enantiotropic nematic mesomorphism. The range of temperatures for the nematic phase Δ tN can be controlled by changing the number of methylene units in the repeating polymer unit. For n = 4, Δ tN = 97°C is the largest that can be obtained. Higher n leads to smaller values of Δ tN. When n = 12, the polyester exhibits only one single C-I transition. For n 〉 12 a smectic mesophase can be expected in this system. Strezlecki and Liébert reported a wide range of temperatures of Δ tN (70-160°C) for the Sn polymers made by the transesterification of 4'-acetoxyphenyl-4-acetoxybenzoate and the dicarboxylic acids. We believe the latter reaction occasionally involves the internal ester linkage in the monomer unit, producing a copolyester having a random distribution of hard segment lengths and changed polymer mesomorphic properties.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260603
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  • 10
    Electronic Resource
    Electronic Resource
    Fiber spinning from the nematic melt. V. Flow instabilities in the 75:25 copolyester of p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 1711-1725 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have investigated the rheological properties of the Celanese copolyester with the composition 75 mol% p-hydroxybenzoic acid and 25 mol% 2-hydroxy-6-naphthoic acid (designated as 75HBA/25HNA). Three different samples having inherent viscosities 3.0, 6.0, and 9.2 dL/g were studied. A flow instability is observed at low shear stress which produces an irregularity in the fiber diameter. The surface irregularity becomes less pronounced above a minimum shear stress, indicating that the flow instability originates in the capillary. For these nematic melts, the minimum shear stress marking the onset of more regular flow is found to decrease with increasing temperature and with decreasing inherent viscosity of the copolyester. The die swell ratio of extrudates decreases with increasing shear stress. Fibers were spun from the samples having ηinh = 9.2 and 3.0 dL/g. The initial modulus and tenacity to break for 75HBA/25HNA fibers spun at sufficiently high shear stress to produce smooth filaments are significantly lower than the values we previously reported for fibers of the 58HBA/42HNA copolyester. Moreover, the optimum properties are obtained at relatively low spin-draw ratios. The 75HBA/25HNA polyester also exhibits a yield stress which decreases with increasing temperature. This observation indicates the presence of crystallities at the test temperatures. We believe that the higher content of HBA in the present copolymer gives rise to crystallization of HBA blocks in the thread line and that defects are introduced at higher spin-draw ratios which cause the mechanical properties to become worse.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260811
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