• Polymer(Korea)
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• v.24 no.3
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• pp.431-436
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• 2000

To improve the thermal and mechanical properties of homo poly(L-lactic acid), DL-mandelic acid, one of the natural $\alpha$-hydroxy acid with aromatic ring as the side-chain residue was used as the comonomer. Copolymers with different contents of mandelic acid were prepared and characterized. The resulting copolymers were mostly amorphous. As the amount of mandelic acid in the monomer feed increased, the molecular weight of the resulting polymers tended to decrease linearly. T$_{g}$ and T$_{d}$ of the copolymer, however, were found to shift toward higher temperature, suggesting the improved thermal stability by increasing content of mandelic acid moiety. Tensile measurements of cast films showed somewhat improved values in the copolymers with mandelic acid content of 5 and 10 wt%.%.%.

• 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.47 no.4
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• pp.355-363
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• 2012

A series of poly(hydroxyamide)s (PHAs) having trifluoromethyl group were prepared by direct polycondensation of aromatic diimide-dicarboxylic acids with 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane by thionyl chloride and triethyl amine in N-methyl-2-pyrrolidinone (NMP). The PHAs exhibited inherent viscosity in the range of 0.54-0.96 dL/g at $35^{\circ}C$ in DMAc solution. All PHAs were readily soluble in a variety of organic solvents, whereas the polybenzoxazoles (PBOs) were quite insoluble except partially soluble in sulfuric acid. PHAs were converted to PBOs by thermal cycling reaction with heat of endotherm. The maximum weight loss temperature of the PHAs occurred in the range of $559-567^{\circ}C$. The PBOs showed relatively high char yields in the range of 47-59%. Pyrolysis Combustion Flow Calorimeter (PCFC) results of the PBOs showed 12-19 W/g heat release rate (HRR), and 2.7-3.6 kJ/g total heat release (total HR). The HRR of PBO 1 showed the lowest value of 12 W/g, which was 37% lower than that of PBO 3 (19 W/g).