• Elastomers and Composites
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• v.53 no.3
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• pp.141-149
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• 2018

A series of aromatic poly(o-hydroxyamide)s (PHAs) were synthesized by the direct polycondensation reaction of 4,4′-(2,3-quinoxalinedioxy) dibenzoic acid and/or 4,4′-(2,3-pyridinedioxy) dibenzoic acid with bis(o-aminophenol) including 2,2-bis-(amino-4-hydroxyphenyl)hexafluoropropane. The PHAs exhibited inherent viscosities in the range of 0.17-0.35 dL/g at $35^{\circ}C$ in a DMAc solution. These polymers showed low inherent viscosities and yielded brittle films. All the PHAs showed excellent solubility in aprotic solvents such as DMAc, DMSO, NMP, and DMF at room temperature and in less polar solvents such as pyridine and THF. However, all the PBOs were only partially soluble in $H_2SO_4$. The PBOs exhibited 10% weight loss at temperatures in the range of $537-551^{\circ}C$. The maximum weight loss temperature increased with an increase in the content of the quinoxaline-containing monomer. The residue of the PBOs showed a weight loss of 45.8-56.7% at $900^{\circ}C$ in a nitrogen atmosphere.

• Korean Journal of Microbiology
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• v.41 no.3
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• pp.225-231
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• 2005

The characteristics of cell growth and medium-chain-length polyhydroxyalkanoate (MCL-PHA) biosynthesis of Pseudomonas chlororaphis HS21 were investigated using plant oils as the carbon substrate. The organism was efficiently capable of utilizing plant oils, such as palm oil, corn oil, and sunflower oil, as the sole carbon source for growth and MCL-PHA production. When palm oil (5 g/L) was used as the carbon source, the cell growth and MCL-PHA accumulation of this organism occurred simultaneously, and a high dry cell weight (2.4 g/L) and MCL-PHA ($40.2\;mol{\%}$ of dry cell weight) was achieved after 30 hr of batch-fermentation. The repeating unit in the MCL-PHA produced from palm oil composed of 3-hydroxyhexanoate ($7.0\;mol{\%}$), 3-hydroxyoctanoate ($45.3\;mol{\%}$), 3-hydroxydecanoate ($39.0\;mol{\%}$), 3-hydroxydodecanoate ($6.8\;mol{\%}$), and 3-hydroxytetradecanoate ($1.9\;mol{\%}$), as determined by GC/MS. Even though glucose was a carbon substrate that support cell growth but not PHA production, the conversion rate of palm oil to PHA was significantly increased when glucose was fed as a cosubstrate, suggesting that bioconversion of some functionalized carbon substrates to related polymers in P chlororaphis HS21 could be enhanced by the co-feed of good carbon substrates for cell growth. In addition, the change of compositions of repeating units in MCL-PHAs synthesized from the plant oils was markedly affected by the supplementation of acrylic acid, an inhibitor of fatty acid ${\beta}-oxidation$. The addition of acrylic acid resulted in the increase of longer chain-length repeating units, such as 3-hydroxydodecanoate and 3-hydroxytetradecanoate, in the MCL-PHAs produced. Particularly, MCI-PHAs containing high amounts of unsaturated repeating units could be produced when sunflower oil and corn oil were used as the carbon substrate. These results suggested that the alteration of PHA synthesis pathway by acrylic acid addition can offer the opportunity to design new functional MCL-PHAs and other unusual polyesters that have unique physico-chemical properties.

• Biotechnology and Bioprocess Engineering:BBE
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• v.1 no.1
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• pp.51-53
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• 1996

Fed-batch culture of Pseudomonas oleovorans was carried out for the production of medium-chain-length polyhydroxyalkanoates (MCL-PHAs) using octanoate as a carbon source. Octanoate and the salt solution containing ammounium sulfate and magnesium sulfate were intermittently fed in the course of fermentation. Cell mass and PHA concentrations of 42.8 and 16.8g/L, respectively, could be obtained in 40 h. The PHA content and the PHA productivity were 39.2% and 0.42 g PHA/L-h, respectively. The yields of cell mass and PHA were 0.71 g dry cell mass/g octanoate and 0.28g PHA/g octanoate, respectively. Therefore, octanoate can be used for the production of MCL-PHAs to a high concentration with high productivity.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2550-2558
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• 2013

Poly(o-hydroxyamides)(PHAs) copolymers having oligo(oxy ethylene) pendant in the main chain were synthesized by solution polycondensation reaction at low temperature. Copolymer precursors were studied by fourier transform infrared(FT-IR), differential scanning calorimeter(DSC), thermogravimetric analyzer(TGA), universal testing machine(UTM) and limited oxygen index(LOI). The inherent viscosities of the PHAs measured at $35^{\circ}C$ in DMAc or DMAc/LiCl solution were in the range of 0.74~1.42 dL/g. Solubility of the precursors with higher oligo(oxy ethylene) unit was increased, but the PBOs were nearly insoluble in a variety of solvents. The degradation temperature of the copolymer precursors was recorded in the ranges of $408{\sim}664^{\circ}C$ in nitrogen and char yields showed 13~59% values at $900^{\circ}C$. The mechanical properties and flame retardancy of copolymer precursors decreased with higher oligo(oxy ethylene) unit.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.2
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• pp.100-109
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• 1999

This study evaluates the pretreatment for analysis of benzidine metabolites in urine by measuring the recovery rates according to the temperature and periods of storage of the urine. By the solid phas e extraction, the recovery rates of basic hydrolysis are benzidine 67.4 %, monoacetylbenzidine 105.1 %, and diacetylbenzidine 115.8 %, respectively. By the liquid extraction, the recovery rates of back-extraction into 0.1 M perchloric acid are benzidine 105.7%, monoacetylbenzidine 94.2 %, diacetylbenzidine 72.8 %, respectively. The difference of the recovery rates between the back-extraction into 0.1 M HCl and 0.1 M perchloic acid after basic hydrolysis are 101 % and 98.8 %, respectively. When the recovery rates of the urinary s amples of pH 3, pH 7, pH 12 at $25^{\circ}C$ and $-76^{\circ}C$ are compared for four weeks, there are no differences according to the temperature and the periods of storage. The above results show that the solid phase extraction and back-extraction by 0.1 M perchloric acid after basic hydrolys is are suitable for the analysis of benzidine metabolites. There are no difference of the recovery rates of the urinary samples stored at $25^{\circ}C$ and $-76^{\circ}C$ at pH 3, pH 7, pH 12, respectively for 28 days.

• Microbiology and Biotechnology Letters
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• v.32 no.2
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• pp.123-127
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• 2004

Pseudomonas sp. MBEL21 was newly isolated from soil samples and found to accumulate medium-chain-length Polyhydroxyalkanoates(MCL-PHAs) using oleic acid as a sole carbon source. Among the various nutrient limiting conditions examined, including nitrogen, sulfur and phosphorus, only phosphorus limitation supported the accumulation of MCL-PHAs up to 15 wt％ of dry cell weight in flask cultures. MCL-PHAs produced by Pseudomonas sp. MBEL21 was mainly composed of 3-hydroxy-5-cis-tetradecenoate. Fed-batch culture of Pseudomonas sp. MBEL21 by novel feeding strategies based on cell growth charcteristics was carried out under phosphorus limitation using oleic acid as a sole carbon source. The final cell concentration and PHA content of 82 g/L and 28 wt％, respectively, were obtained. Furthermore, PHA consisted of MCL-hydroxyalkanoates and 3-hydroxybutyrate could be produced using olive oil as a sole carbon source.

• Elastomers and Composites
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• v.43 no.4
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• pp.271-280
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• 2008

Aromatic polyhydroxyamides (PHAs) having bulky groups and ether linkages in the polymer main chain were synthesized by the low temperature solution polycondensation reaction. FT-IR, $^{1}H-NMR$, DSC, and TGA were used to study the properties of these polymers. The PHAs were converted into polybenzoxazoles (PBOs) by a thermal cyclization reaction, and endothermic peaks were observed in the range of $220{\sim}400^{\circ}C$. The introduction of the ether and bulky groups in the main chain improved the solubility of the PHAs in aprotic solvents such as DMSO and DMF, but the PBOs were nearly insoluble in common solvents. All the PBOs, except for PBO 5 with 2,6-dimethylphenoxy pendant and 2,3-dihydroxyquinoxaline ring, and PBO 6 with 2,6-dimethylphenoxy pendant and 2,3-dihydroxyquinoxaline ring, exhibited $T_g's$ in the range from 149 to $217^{\circ}C$ by DSC. The thermogravimetric analyses indicated that most of the PBOs were thermally stable up to $400^{\circ}C$ in nitrogen. Maximum weight loss temperatures of PHA 5 and PBO 5 with 2,6-dimethylphenoxy pendant and 2,3-dihydroxyquinoxaline ring were $707^{\circ}C$ and $683^{\circ}C$, respectively, which were the hightest temperatures among the corresponding copolymers. The PBOs in nitrogen exhibited relatively high char yields in the range of $63{\sim}70%$ at $900^{\circ}C$.

• Elastomers and Composites
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• v.46 no.4
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• pp.295-303
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• 2011

A series of new aromatic polyhydroxyamides (PHAs) containing imide ring were prepared by direct polycondensation reaction of imide-diacids and two types of bis(o-aminophenol)s including 3,3'-dihydroxybenzidine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. The polymers were characterized by FT-IR, FT-NMR, DSC and TGA. The inherent viscosities of the PHAs measured at $35^{\circ}C$ in DMAC solution were in the range of 0.49-1.13 dL/g. PHA 2 and 3, except PHA 1, were soluble in polar solvents such as DMAc, DMF and NMP. PHA 4, 5, and 6 containing 6F group showed a higher solubility in less polar solvents. But the polybenzoxazoles (PBOs,) were insoluble in a variety of solvents except partially soluble in sulfuric acid. The PBO 1, 2 and 3 showed maximum weight loss temperature in the range of $650-656^{\circ}C$ and relatively high char yields in the range of 57.4-61.9 % under a nitrogen atmosphere. These results suggested that the introduction of imide or diimide ring in the main chain was effective in improving the thermal stability of PHAs and PBOs.

• Elastomers and Composites
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• v.42 no.4
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• pp.238-248
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• 2007

A series of polyhydroxyamides(PHAs) having ether linkages in the polymer backbone were prepared via solution polycondensation at low temperature. These polymers were studied by FT-IR, $^1H-NMR$, DSC, TGA and PCFC. The PHAs exhibited inherent viscosities in the range of $0.5{\sim}1.1dL/g\;at\;35^{\circ}C$ in DMAc solution. Most of PHAs except PHA 3 were soluble in polar organic solvents such as N,N-dimethylacetamide(DMAc), N-methyl-2-pyrrolidone(NMP), and N,N-dimethylform-amide(DMF). Subsequent thermal treatment of PHAs afforded polybenzoxazols(PBOs). However, the PBOs were insoluble in a variety of solvents. Most of the PBOs except PBO 3 showed glass-transition temperature($T_g$) in the range of $200{\sim}246^{\circ}C$ by DSC and maximum weight loss temperature in the range of $597{\sim}697^{\circ}C$ in nitrogen by TGA. PBOs showed high char yields in the range of $51{\sim}64%$. PCFC results of the PBOs showed the heat release(HR) capacity, $8{\sim}65J/gK$ and total heat release(total HR), $2.4{\sim}4.7kJ/g$.