Synthesis and structure of the <i>p</i>‐hydroxybenzoic acid polymer

Economy, James; Storm, R. S.; Matkovich, V. I.; Cottis, Steve G.; Nowak, B.

doi:10.1002/pol.1976.170140911

Cited by 238 publications

(132 citation statements)

References 5 publications

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“…29 Since the peak around 20 20° of PHB/PET is close to the (220) reflection of the crystal of PHB homopolymer, 30 this peak might indicate the lateral spacing probably due to PHB-rich regions in the mesophase. In Figure 2, the molecular spacing is plotted against the temperature both for the oriented and unoriented samples.…”

Section: Resultsmentioning

confidence: 99%

Thermal Expansion of a 60 mol% para-Hydroxybenzoic Acid/40 mol% Ethylene Terephthalate Liquid Crystalline Copolyester Oriented in a Magnetic Field

Kimura

Maeda

Sata

et al. 1995

Polym J

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ABSTRACT:The thermal expansion is investigated for a 60mol% para-hydroxybenzoic acid/40mol% ethylene terephthalate liquid crystalline copolyester oriented in a magnetic field (6T). The high-temperature expansion coefficient of the oriented samples shows an anisotropy; it is negative (shrink) to the orientation direction, while it is positive (expand) to the direction perpendicular to the orientation. The X-ray diffraction measurement indicates that the positive expansion coefficient is attributed to the increase in the mean spacing of the oriented chains.KEY WORDS Thermal Expansion/ Magnetic Orientation/ Liquid Crystals/ Poly( ethylene terephthalate-co-p-oxybenzoate) / Thermotropic Copolyester / Thermotropic liquid crystalline copolyesters 1 provide high-strength materials when they are oriented. The molecular orientation of these polymers is usually attained by the external forces such as shear and elongation stresses applied through the extrusion or molding processes. These forces, however, do not apply homogeneously throughout a sample, resulting in imperfect orientations, even in a skin-core structure in the case of shear. 2 A magnetic field is an alternative for attaining molecular orientations. 3 -5 This is due to the diamagnetic anisotropy of the backbone structure of the polymers and to the propensity of these polymers to form mesophase.

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Section: Resultsmentioning

confidence: 99%

Thermal Expansion of a 60 mol% para-Hydroxybenzoic Acid/40 mol% Ethylene Terephthalate Liquid Crystalline Copolyester Oriented in a Magnetic Field

Kimura

Maeda

Sata

et al. 1995

Polym J

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“…In the literature, both Kricheldorf [5] and Economy [4] mention 4-phenoxybenzoic acid as a byproduct in LCP preparation; it could be formed through nucleophilic aromatic substitution (Scheme 7). This would correspond to nucleophilic aromatic displacement, a reaction for which the polymer structure is very well adapted.…”

Section: Other Possible Side Reactions During the Lcp Polymerizationmentioning

confidence: 99%

“…This inexpensive ingredient is incorporated into linear aromatic polyesters and confers a rod-like structure to them. Unfortunately the homopolymer is quite intractable, melting at >500 °C and only slightly soluble in pentafluorophenol [4]. Accordingly, comonomers such as terephthalic acid and hydroquinone or 6-hydroxy-2-naphthoic acid (HNA) are added to make the polymers tractable and processable, so that commercial LCP's are always copolymers.…”

Section: Open Accessmentioning

confidence: 99%

Mechanism Studies of LCP Synthesis

Padías

Hall

2011

Polymers

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Abstract:The LCP (Liquid Crystal Polymer) known as Vectra is synthesized by acidolysis of 4-hydroxybenzoic acid with 6-hydroxy-2-naphthoic acid. The apparently simple acidolysis mechanism for LCP polycondensation is in fact a complex blend of mechanisms. Kinetics of model reactions and of actual polycondensations followed second-order kinetics and their rate constants were comparable. In the latter stages, ketene loss leads to phenolic ends, while decarboxylation provides phenyl ester ends. Accordingly, the mechanism changes to phenolysis. A quinone methide intermediate may also intervene, as revealed by kinetics studies and MALDI-TOF spectroscopy. Tailor-made matrices and synthesis of alternating well-defined oligomers assisted our studies. Nucleophilic aromatic substitutions may play a role, and we speculate on possible chain polycondensation. Esterolysis may be a useful alternative to LCP synthesis. Complications caused by ketene loss can be averted by the use of methoxycarbonyloxy monomers.

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“…POB has the similar problem derived from its intractability, and hence many thermotropic polyesters composed of p-oxybenzoyl unit as well as other aromatic copolyesters have been developed thus far. [3][4][5][6][7][8][9] Thermotropic polyesters composed of p-oxybenzoyl unit are modified to reduce the chain rigidity by copolymerization, and therefore sacrifices the eventual properties predicted from the chain structure of POB. We have succeeded in obtaining whiskers of POB and other aromatic polyesters using crystallization of oligomers during solution polymerization.…”

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Preparation of Poly(p-oxybenzoyl) Whisker in Paraffin Wax

Sarker

Kimura

Yamashita

2002

Polym J

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ABSTRACT:An influence of solvent on morphology as well as growth mechanism of poly(p-oxybenzoyl) whisker in paraffin wax (PW) was studied comparing with those in liquid paraffin (LPF). Furthermore, the condition for consecutive addition of oligomer was also examined to lengthen the whiskers in PW. Polymerizations of p-acetoxybenzoic acid were carried out in PW and LPF at 330• C. Larger number of whiskers having smaller length and width were formed in PW compared with that in LPF. PW was a poorer solvent than LPF and this lower miscibility leaded to the crystallization of lower DP n oligomers. Additionally, formation rate of oligomer was bigger in PW than LPF. These facts resulted in the higher degree of super saturation of oligomers which generated a larger number of nuclei having smaller size. Since the length was determined by the number of nuclei and the yield, the length eventually became shorter. On the basis of the formation mechanism of the whisker in PW, oligomers were added into polymerization system to lengthen the whisker. When oligomers were added to compensate the consumed oligomers while the tip angle was constantly kept at 80• C, the steady growth period was expanded and the length increased from 13.4 µm to 22.1µm. KEY WORDS Poly(p-oxybenzoyl) / Whisker / Paraffin Wax / Crystallization / Oligomer / Miscibility / Aromatic polyesters are characterized by the unique combination of thermal and mechanical properties and by a remarkable chemical resistance, which makes them useful high performance materials for various industrial applications such as reinforcement of composites, substitutions for asbestos and so on. However, wholly aromatic polyesters consisted of rigid-rod molecules show usually neither solubility or metlability under their decomposition temperatures. This intractability brings them about severe problems in industrial usage. Many attempts have been conducted with the aim of improving the poor processability from the point of both chemical modifications 1 and processing techniques. 2 Poly(p-oxybenzoyl) (POB) is a wholly aromatic polyester consisted of rigid-rod molecule and it is a hopeful candidate as high performance materials. POB has the similar problem derived from its intractability, and hence many thermotropic polyesters composed of p-oxybenzoyl unit as well as other aromatic copolyesters have been developed thus far. 3-9 Thermotropic polyesters composed of p-oxybenzoyl unit are modified to reduce the chain rigidity by copolymerization, and therefore sacrifices the eventual properties predicted from the chain structure of POB. We have succeeded in obtaining whiskers of POB and other aromatic polyesters using crystallization of oligomers during solution polymerization. [10][11][12][13][14][15][16][17][18][19] POB whiskers are prepared from p-acetoxybenzoic acid (p-ABA) in poor solvent such as liquid paraffin (LPF) with the elimination of acetic acid at high temperature solution polymerization, of which the average length is ca. 40 µm and the average width is 1.5 µm. These whiske...

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Synthesis and structure of the p‐hydroxybenzoic acid polymer

Cited by 238 publications

References 5 publications

Thermal Expansion of a 60 mol% para-Hydroxybenzoic Acid/40 mol% Ethylene Terephthalate Liquid Crystalline Copolyester Oriented in a Magnetic Field

Thermal Expansion of a 60 mol% para-Hydroxybenzoic Acid/40 mol% Ethylene Terephthalate Liquid Crystalline Copolyester Oriented in a Magnetic Field

Mechanism Studies of LCP Synthesis

Preparation of Poly(p-oxybenzoyl) Whisker in Paraffin Wax

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