Structures of wholly aromatic copolyesters composed of 4-hydroxybenzoic acid, biphenol and terephthalic acid: 1. Effects of copolymer composition on thermal properties

Yonetake, Koichiro; Takahashi, Atsushi; Masuko, Tōru; Murouchi, Satoshi; Kobayashi, Toshitaka

doi:10.1016/0032-3861(95)90985-b

Cited by 10 publications

(6 citation statements)

References 9 publications

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“…Consequently, the two peaks merged together with increasing annealing temperature. Similar observations on the annealing of LC polyesters were reported by Yonetake et al15 The temperature of annealing has a definite effect in premelting behavior 16. At still higher temperatures during annealing, the shift of the low‐temperature endotherm is much more than that during low‐temperature annealing.…”

Section: Resultssupporting

confidence: 81%

Synthesis, characterization, and in vitro degradation of liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid/3‐(4‐hydroxyphenyl)propionic acid with terephthalic acid and 2,6‐naphthalene diol

Prasad

Pillai

2002

J. Polym. Sci. A Polym. Chem.

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Melt-processable liquid-crystalline terpolyesters of 4-hydroxyphenylacetic acid (HPAA) and 3-(4-hydroxyphenyl)propionic acid (HPPA) with terephthalic acid and 2,6-naphthalene diol were synthesized by one-step acidolysis melt polycondensation followed by postpolymerization and were characterized with viscosity studies, Fourier transform infrared (FTIR) and NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarized light microscopy, and wide-angle X-ray diffraction. The melting behaviors and liquid-crystalline transition temperatures of the terpolyesters were dependent on the composition of the HPAA/HPPA content. The transition temperatures of the polyesters could be effectively reduced by the introduction of an even number of built-in short methylene spacers in combination with the 2,6-naphthalene offset structure. A terpolyester with an HPPA content of 33% (NTP33) showed optimum properties for the glass-transition temperature, around 71°C, and the melting temperature, near 240°C, with a Schlieren nematic texture. The polymer showed excellent flow behavior in a Brabender plasticorder. It was also thermally stable up to 400°C. NTP33 showed 2.5% in vitro hydrolytic degradation in buffer solutions of pH 10 at 60°C after 540 h. Considerable enzymatic degradation was also observed with porcine pancreas lipase/buffer solutions in comparison with Candida rugosa lipase after 60 days. The degradation was also followed with FTIR, DSC, and TGA. Apart from the temperature and pH of the buffer solution, several structural parameters, such as the aromatic content, crystallinity percentage, and composition of the polymer, affected the degradation behavior. FTIR studies indicated the involvement of chain scission during degradation. Scanning electron microscopy studies further showed that surface erosion also played a major role in the degradation.

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Section: Resultssupporting

confidence: 81%

Synthesis, characterization, and in vitro degradation of liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid/3‐(4‐hydroxyphenyl)propionic acid with terephthalic acid and 2,6‐naphthalene diol

Prasad

Pillai

2002

J. Polym. Sci. A Polym. Chem.

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“…Biphenols and their derivatives are important compounds in the various research fields ranging from chemistry to biology and medicine. − 2,2‘-Biphenol is a fundamental biphenol owing to its ability to form inter- and intramolecular hydrogen bondings. , Another particular aspect of 2,2‘-biphenol is that it has a chirality feature. Indeed, the restricted rotation around the C−C inter-ring σ-bond in 2,2‘-biphenol may generate a mirror image if the hydroxy (OH) groups conserve their initial rotations, that is, without any internal rotation of the OH groups around the C−O bonds, or may lead to the formation of other isomers while maintaining OH initial rotational angles.…”

Section: Introductionmentioning

confidence: 99%

Density Functional Theoretical Study on Enantiomerization of 2,2‘-Biphenol

2006

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The S-R enantiomerization processes of 2,2'-biphenol (biphenol) have been investigated using density functional theory (DFT). Five isomers for biphenol were identified: I0, which is the most stable isomer; I1a and I1b, which are formed by a restricted rotation of one OH group; and I2a and I2b, which are formed by a restricted rotation of the two OH groups where a and b denote cis and trans configurations, respectively. Each isomer has R- and S-enantiomers. The energies relative to the most stable isomer I0 are 1.6, 3.3, 5.3, and 5.5 kcal mol(-1) for I1a, I1b, I2a, and I2b, respectively. The direct enantiomerization of I0, in which the phenol-ring rotation is considered to be the reaction coordinate while the OH rotations are frozen, is forbidden because of the repulsion between the two OH groups. The transition states for isomerizations of I0 to other isomers (I1a, I1b, I2a, or I2b) were calculated as well as those for the other direct enantiomerizations except for that of I0. From the viewpoint of the least number of the transition states and their low energy levels, the probable S-R enantiomerization of I0 is expressed as a sequential process of isomerization: I0,S --> I1a,S, a direct enantiomerization induced by one of the two OH rotations, I1a,S --> I1a,R, and another isomerization, I1a,R --> I0,R, that is, I0,S --> I1a,S --> I1a,R --> I0,R as the whole process. This process is effective in quantum control of the enantiomerization of biphenol and can be carried out by a sequence of a pump-dump IR laser-pulse scheme.

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“…All of the copolyesters, derived from phenyl-substituted 4,4‘-biphenols, terephthalic or 2,6-naphthalenedicarboxylic acid, and 50 mol % 4,4‘-oxybis(benzoic acid), had much lower fusion temperatures, T f , than the T m values (400−470 °C) of Xydar family of copolyesters (based on BP, TA, and HBA), which would facilitate their processing at temperature as low as 180 °C from their nematic melts. Each of them showed a nematic phase above its T f value, which showed both the threaded and schlieren texture.…”

Section: Discussionmentioning

confidence: 99%

Crystalline and Liquid Crystalline Polyesters of Phenyl-Substituted 4,4‘-Biphenols. 5. Copolymers with 4,4‘-Oxybis(benzoic acid)

et al. 1996

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Wholly aromatic, thermotropic copolyesters, derived from either 3-phenyl-4,4‘-biphenol (MPBP) or 3,3‘-diphenyl-4,4‘-biphenol (DPBP) with either terephthalic acid (TA) or 2,6-naphthalenedicarboxylic acid (NDA) and 50 mol % 4,4‘-oxybis(benzoic acid) (OBBA), were prepared by the melt polycondensation reaction, and their liquid crystalline properties were characterized by a number of experimental techniques. The solubility of these polyesters in common organic solvents had also been studied. They had lower fusion temperatures, T f, than the T m values of the copolyesters of 4,4‘-biphenol, TA, and 4-hydroxybenzoic acid. Their low T f values were because of increased entropy of the respective monomers. Each of them exhibited a nematic phase above its T f value that contained both the threaded and schlieren texture. The two copolyesters of MPBP and hand-drawn fibers therefrom showed a banded texture that could be preserved for a prolong period of time. Each of them showed a nematic-to-isotropic transition as determined by the polarizing light microscope studies. The copolyesters of MPBP had a much broader range of mesophase than those of DPBP. The two copolyesters of DPBP exhibited a biphase behavior at lower temperatures than those of the copolyesters of MPBP. Their random microstructures were confirmed with the WAXD studies of oriented fibers and the 13C-NMR spectroscopy, whenever possible. No development of crystallinity occurred in these copolyesters even on annealing. They had relatively high glass transition temperatures, T g, in the range of 149−171 °C when compared with other liquid crystalline polyesters and good thermal stability, T d, in the range of 413−436 °C. Since they had no detectable crystallinity, the copolyesters of either MPBP or DPBP with TA and OBBA were soluble in common organic solvents, but those with NDA and OBBA were not soluble in these solvents.

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Structures of wholly aromatic copolyesters composed of 4-hydroxybenzoic acid, biphenol and terephthalic acid: 1. Effects of copolymer composition on thermal properties

Cited by 10 publications

References 9 publications

Synthesis, characterization, and in vitro degradation of liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid/3‐(4‐hydroxyphenyl)propionic acid with terephthalic acid and 2,6‐naphthalene diol

Synthesis, characterization, and in vitro degradation of liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid/3‐(4‐hydroxyphenyl)propionic acid with terephthalic acid and 2,6‐naphthalene diol

Density Functional Theoretical Study on Enantiomerization of 2,2‘-Biphenol

Crystalline and Liquid Crystalline Polyesters of Phenyl-Substituted 4,4‘-Biphenols. 5. Copolymers with 4,4‘-Oxybis(benzoic acid)

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