• Proceedings of the Korean Fiber Society Conference
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• 1987.06b
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• pp.13-14
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• 1987

• Elastomers and Composites
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• v.55 no.3
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• pp.205-214
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• 2020

A series of wholly aromatic polyhyroxyamide (PHA) copolymers were prepared by direct polycondensation reaction of isophthalic acid and diacids containing bulky units with 3,3'-dihydroxybenzidine. The inherent viscosities of the PHAs measured at 35℃ in DMAc solution were in the range of 0.31-0.56 dL/g. The solubility study revealed that the PHAs were readily soluble in aprotic solvents such as, dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP) at room temperature and in less polar solvent such as pyridine. However, the polybenzoxazole (PBO) copoymers were quite insoluble in all organic solvents except partially soluble in concentrated sulfuric acid and partially soluble in NMP containing LiCl. The PBO copolymers showed maximum weight loss temperature in the range of 593-632℃ and high char yields in the range of 65.0-71.2% at 900℃ in a nitrogen atmosphere.

• Polymer Science and Technology
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• v.18 no.1
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• pp.26-31
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• 2007

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.4041-4046
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• 2010

Wholly aromatic polyesters having flexible alkoxy side chain were synthesized by direct polycondensation. The synthetic polymers have been characterized by $^1H$-NMR, FT-IR. DSC, TGA, optical polarizing microscope and X-ray diffractometer. The inherent viscosities (${\eta}_{inh}$) measured in 1,1,2,2-tetrachloroethane (TCE) were 0.46~2.41 dL/g. The polymers having side chain showed double melting transition, ie, solid-sanidic liquid crystalline (LC) phase transition ($T_{m1}$) and sanidic LC phase-nematic LC phase transition ($T_{m2}$). As incresing length of alkoxy side chain, phase transition temperatures decreased and solubilities in organic solvents incresed. The peaks of $2{\theta}\;{\simeq}5$ and $2{\theta}\;{\simeq}20$ in X-ray diffractograms are due to crystallization of polymer main chain and of long side chain, respectively.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.347-350
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• 2002

Wholly aromatic polybenzoxazoles(PBO) are well established as high performance materials with excellent thermal stability and mechanical properties. Heterocyclic precursor polymers such as polyhydroxyamides(PHA) have been interested in the field of high performance flame retardant polymers.[1] Precusor polymers have the advantages that they are easier to process, don't require strong solvents and can adsorb large amounts of heat energy during the cyclization process. (omitted)

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.41-44
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• 1998

Wholly aromatic polybenzoxazoles (PBO) are well established as high performance materials with excellent thermal stability and mechanical properties. Heterocyclic precursor polymers such as polyhydroxyamides (PHA) have been interested in the field of high performance flame retardant polymers. The PHAs can be converted to PBOs when ignited. (omitted)

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.361-363
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• 2001

Aromatic pelybenzoxazoles(PBOs) display excellent thermal stability plus good solvent and chemical resistance. Wholly aromatic PBOs, in fact, are soluble only in strong acids(e.g., sulfuric, rmethanesulfonic, triflic, and polyphosphoric acids). However, fully heterocyclized polymers have shown some drawbacks in solubility and processing. This problem of processing is currently being exploited to obtain unusual combinations of physical properties in fibers and films. (omitted)

• Polymer(Korea)
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• v.29 no.6
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• pp.523-535
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• 2005

Linear aromatic polyesters are representative examples of thermotropic liquid crystalline polymers (TLCPs), which have been the subject of many researches. This article reviews the structure-LC properties relationship in wholly aromatic CLCPs mostly based on the results obtained for the past quarter of a century. Especially, this review deals with the structural details of aromatic polyester TLCPs that influence the liquid crystalline and thermal properties. In the last part of this article the liquid crystalline properties of combined type and hyperbranched polyester also are discussed. Introduction to various synthetic methods are included in the last section.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3060-3065
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• 2009

A series of wholly aromatic Poly(ether-ether-ester)s with flexible side chain was synthesized by direct polycondensation from ether linkaged triad diol and 2,5-dialkoxyterephthalic acid. The chemical structures and physical properties of these polymers were investigated by using $^1H$-NMR, FT-IR, DSC and TGA. As results of investigations, the inherent viscosities($\eta$inh) measured at $40^{\circ}C$ in 1,1,2,2-tetrachloroethane(TCE) were 0.45~0.86 dl/g and initial decomposition(Td) in TGA occurred at 378~418 $^{\circ}C$ in N2 gas. The majority of these polymers were soluble in organic solvents used in this experiments at elevated temperatures. Melting temperatures(Tm) decreased with increasing the length of the side chain and showed odd-even effects.

• Polymer(Korea)
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• v.36 no.1
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• pp.9-15
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• 2012

We prepared a series of aromatic liquid crystals (LCs) based on wholly aromatic ester units with the reactive end group methyl maleimide by means of melt condensation method, and the resulting LCs were thermally crosslinked to produce liquid crystalline thermoset (LCT) films. The synthesized LCs and LCTs were characterized with Fourier transform infrared (FTIR) spectroscopy, wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomechanical analysis (TMA), and polarizing optical microscopy (POM) with a hot stage. The glass transition temperature ($T_g$) and coefficient of thermal expansion are strongly affected by the mesogen units in their main chain structures. The $p$-substituted biphenyl LC was found to have the highest thermal property value.