• Polymer(Korea)
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• v.29 no.2
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• pp.183-189
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• 2005

Films of poly(vinyl alcohol)(PVA)/chitosan blends and its blend hydrogels were prepared by the solution casting method. The state of miscibility of the blends and blend hydrogels were examined over the entire composition range by differential scanning carorimetry (DSC), thermogravimetry (TGA), and dynamic mechanical analysis (DMA). DSC analysis shows the depression of melting point of PVA in the blends and the decrease of crystallization temperature of PVA in the blends were observed with increasing chitosan content in the blends. TGA analysis indicates that chitosan was thermally more stable than PVA and the thermal stability of PVA in the blends was higher than that of pure PVA, due to some interactions between two component polymers in the blend. The glass transition temperature $(T_g)$ of the chitosan and of PVA, measured by DMA, were at 160 and $90^{\circ}C$, respectively. The $T_g$ of the blends was changed with the content of chitosan in the blends. The results of thermal and viscoelastic analysis indicate some miscibility between component polymers in the blend exists. Moisture and cross linking in the blend and blend hydrogel, which strongly change thermal and physical properties of hydrophilic polymers, affected the miscibility of chitosan and PVA to a small extent.

• Polymer(Korea)
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• v.30 no.6
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• pp.519-524
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• 2006

Poly(4-vinyl pyridine) (PVP) and its copolymers, poly(4-vinyl pvridine- co-acrylamide) and poly(4-vinyl pyridine-co-allylamine), were synthesized and evaluated for application to organic solder-ability preservatives (OSP). The copolymers were synthesized by radical polymerization of vinyl pyridine in the presence of acrylamide or allylamine as a comonomer. Various kinds of polymers with different chemical composition were synthesized by varying the feed ratio of monomers and their low $M_w$ polymers can be obtained by adding 2-mercaptoethanol as a chain transfer agent during poly-merization. All the polymers showed good adhesion properties on Cu pad when they were spin-coated. Especially, allylamine -containing copolymers showed both good adhesion and solubility properties. Also, they exhibited better thermal stability than PVP homopolymer and such thermal properties were changed depending on the chemical composition and their $M_w$, which were evidenced by the measurement of oxygen induced temperature (OIT). From the OIT measurement, poly(4-vinyl pyridine- co-allylamine) was thermally stable up to $230^{\circ}C$ for 70 min in the 100% oxygen environment. As a result, allylamine-containing copolymers can be considered as a promising OSP coating material that has excellent thermal and adhesive properties applicable to the present microelectronic package processes.

• Polymer(Korea)
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• v.34 no.6
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• pp.547-552
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• 2010

Biodegradable polymers have gained enormous attentions in the pharmaceutical and biomedical applications, especially in drug delivery. In this work, we report the synthesis and characteristics of high molecular weight polyoxalate with ~75000 Da. Hydrolytic degradation kinetics and degradation products were characterized by nuclear magnetic resonance and gel permeation chromatography. Polyoxalate is a semicrystalline and thermally stable polymer with a glass transition temperature of ${\sim}35^{\circ}C$, which is suitable for drug delivery applications. The hydrophobic nature of polyoxalate allows it to be formulated into nanoparticles and encapsulate drugs using a conventional oil-in-water emulsion/solvent displacement method. Polyoxalate nanoparticles also exhibited excellent cytotoxicity profiles. It can be suggested that polyoxalate has great potential for numerous biomedical and pharmaceutical applications.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.06a
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• pp.72-72
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• 2001

Plasma polymerized thin films have been deposited on Si(lOO) substrates at $25-400^{\circ}C$ using thiophene ($C_4H_4S$) precursor by plasma assisted chemical vapor deposition (PACVD) method for low-dielectric device application. In order to compare physical properties of the as-grown thin films, the effects of the plasma power, gas flow ratio and deposition temperature on the dielectric constant and thermal stability were mainly studied. XRD and TED studies revealed that the as-grown thin films have highly oriented amorphous polymer structure. XPS data showed that the polymerized thin films that grown under different RF power and deposition temperature as well as different gas ratio of $Ar:H_2$ have different stoichiometric ratio of C and S compared with that of monomer, indicating a formation of mixture polymers. Moreover, we also realized that oxygen free and thermally stable polymer thin films could be grown at even $400^{\circ}C$. The results of SEM, AFM and TEM showed that the polymer films with smooth surface and sharp interface could be grown under various deposition conditions. From the electrical property measurements such as I-V and C-V characteristics, the minimum dielectric constant and the best leakage current were obtained to be about 3.22 and $10-11{\;}A/\textrm{cm}^2$, respectively.

• Korean Journal of Food Science and Technology
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• v.37 no.4
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• pp.567-573
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• 2005

Compatability of films made of chitosan, gelatin, and their blends prepared by aqueous solution casting was investigated using a thermogravimetric analyzer(TGA) and a dynamic mechanical analyzer (DMA). TGA showed gelatin is more thermally stable than chitosan, and thermal stability of chitosan in blends was higher than that of pure chitosan due to interaction among functional groups of component polymers in blend. Glass transition temperature $(T_g)$ of blends was dependent on chitosan content of blends. Blend films exhibited good miscibility. Moisture and glycerol contents of blend strongly affected thermal properties of two component polymers.

• 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 $900^{\circ}C$.

• Polymer(Korea)
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• v.25 no.4
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• pp.496-502
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• 2001

Thermally stable polyquinonediimines(PQDI) containing di-azobenzene in the side chain were synthesized by means of condensation polymerization under $TiCl_4$. The synthesized monomers and polymers were identified by FT-IR, $^1H-NMR$, and elemental analysis. Especially, the polymerization of PQDI was confirmed by the double-bonding peak of >C=N appearing near 1625cm$^{-1}$ in FT-IR spectrum. PQDI with di-azobenzene group in one side chain was insoluble in methanol, acetone and non-polar solvents having big dielectric constant, but had good solubility in polar solvents having small dielectric constant. Molecular weight distribution of PQDI measured by GPC was 1.38. It was confirmed to be amorphous polymer through X-ray diffraction by the appearance of the halo in case of PQDI containing di-azobenzene in the side chain. The glass transition temperature ($_g$) of synthesized polymer was measured to be 116$^{\circ}C$ by differential scanning calorimetry. The SHG value for ${\chi}^{(2)}$ was 1.2 pm/V (${\lambda}$ = 1.542 ${\mu}$m). The SHG value slightly decreased in an early stage but showed temporal stability after 20 hours.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.1-7
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• 2017

As a part of studies to lower the infrared (IR) emissivity from the surface of exhaust nozzle in the turbo jet engine, stainless steel plate was coated with copper particle/meta-aramid resin composites and the IR emissivity of the plate were investigated. Binders of filler particles based on synthetic polymers generally undergo thermal decomposition before $300^{\circ}C$. It was found that the meta aramid resin was thermally stable after the test at $320^{\circ}C$, confirming the excellent thermal stability. Contents of copper particles in the composites were varied from 0 to 70% by volume. It was observed that the copper particle/meta aramid resin composites showed good adhesion after the tests at $320^{\circ}C$. The specimen coated with the composite containing 50 vol% of copper particles showed the lowest IR emissivity, 0.6, at $320^{\circ}C$.