• Fibers and Polymers
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• v.7 no.4
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• pp.398-403
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• 2006

Dimensional constants (k values) of single jersey fabrics made from $LincLITE^{(R)}$ and conventional yams are calculated under dry, steam, full relaxation treatments. Fabrics were made under different tightness factors such as high, medium and low with different twist factors, twist directions and feeder blending. $LincLITE^{(R)}$ yarns made to get soft and bulkier effects with yam count of 39 tex and conventional yams made into 39 tex and 48 tex yam counts. Various effects on K values are analysed using correlation coefficients. K-values are increased with relaxation progression and have shown some differences between in $LincLITE^{(R)}$ and conventional fabrics, and feeder blended fabrics. Loop shape factor is highly affected by tightness factor, relaxation and feeder blending in $LincLITE^{(R)}$ fabrics, whereas twist factor not significantly effects on loop shape factor in conventional fabrics. Stitch density significantly increases with relaxation in conventional fabrics and no significant effect shows with $LincLITE^{(R)}$ fabrics.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.471-475
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• 1987

Fe(II)-poly(D-glutamic acid) (PGA) complex in aqueous solution has been investigated as functions of pH and concentration of Fe(II) by using absorption and circular dichroism spectroscopies. The helix-breaking interaction occurred at pH 4.3 while the helix-directing one occurred at pH 5.7 after forming complex between PGA and Fe(II). The relationship between conformation change of PGA by forming complex with Fe(II) and complex constants for the above system was studied. As a result, stability constants in random coil structure of PGA are larger than those in ${\alpha}$-helix structure. This result indicates that the random coil structure of PGA-Fe(II) complex shows more stable complex than ${\alpha}$-helix one.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.434-443
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• 1987

The formation constants of the complexes between Ln-EDTA 1 : 1 complex and IMDA have been investigated by a potentiometric titration method at 20.0${\pm}$0.2 degree C and ${\mu}$ = 0.1 (KNO$_3$). Unusually large stability in Ln(EDTA) mixed ligand complexes was found. Trends in the formation constants vs. atomic number of the lanthanide metals were discussed on the basis of coordination number and ionic radius of the metals.

• Journal of the Korean Chemical Society
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• v.32 no.5
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• pp.464-475
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• 1988

The complex formation of p-aminoazobenzene and its derivatives with Fe(III) and Mn(II) has been studied by UV and IR spectroscopy and conductometry. The effects of solvents, donor basicity, and other factors on the formation of these complexes have been examined. The vatio of metal to ligand for the complexes formed is 1 : 1, both in the solid state and in solution. The stability constants of Fe(III)-donor and Mn(II)-donor complexes are in the range of 10$^2$∼10$^4$ and 0.1∼1, respectively. The absorptivities are ~10$^4$ and ∼10$^3$ l/mol${\cdot}$cm respectively. Thermodynamic properties such as ${\Delta}H^{\circ}$, ${\Delta}G^{\circ}$ and ${\Delta}S^{\circ}$ are calculated from their stability constants utilizing Van't Hoff equation.

• Macromolecular Research
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• v.15 no.2
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• pp.114-128
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• 2007

Polyimides are one of the most important classes of polymers used in the microelectronics and photoelectronics industries. Because of their high thermal stability, chemical resistance, and good mechanical and electric properties, polyimides are often applied in photoresists, passivation and dielectric films, soft print circuit boards, and alignment films within displays. Recently, fully aliphatic and alicyclic polyimides have found applications as optoelectronics and inter layer dielectric materials, due to their good transparencies and low dielectric constants $(\varepsilon)$. The low molecular density, polarity and rare probability of forming inter- or intra-molecular charge transfers, resulting in lowering of the dielectric constant and high transparency, are the most striking characteristics of aliphatic polyimide. However, the ultimate end use of polyimides derived from aliphatic monomers is in their targeted applications that need less stringent thermal requirements. Much research effort has been exerted in the development of aliphatic polyimide with increased thermal and mechanical stabilities, while maintaining their transparencies and low dielectric constants, by the incorporation of rigid moieties. In this article, the recent research process in synthesizing fully aliphatic polyimides, with improved dimensional stability, high transparency and low $\delta$values, as well as the characterizations and future scope for their application in micro electric and photo-electronic industries, is reviewed.

• Macromolecular Research
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• v.15 no.2
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• pp.185-190
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• 2007

Poly(norbornene dimethyl dicarboxylate)s, (PNDMD)s, were prepared by addition polymerization with palladium(II) catalyst from pure exo-monomers, and their structure and properties were compared with those of poly(norbornene dicarboxylic acid dialkyl ester)s, (PNDADA)s. Both polymer series exhibited good solubility in general organic solvents and excellent thermal stability up to $330^{\circ}C$. Wide-angle X-ray scattering (WAXS) study indicated the presence of nano-scale layer-like order in amorphous PNDADAs, while PNDMDs showed random amorphous structure. The glass transition temperatures and dielectric constants of solid polymers were found to decrease as the alkyl side-chain length increases for both polymer series. However, PNDMDs showed lower glass transition temperatures and higher dielectric constants, as compared with those of PNDADAs containing the same alkyl substituents. This difference, caused by the higher side-group mobility of PNDMDs, may be closely related to the nano-scale order in amorphous PNDADAs and its absence in PNDMDs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.5
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• pp.394-399
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• 1998

High power characteristics with vibration velocity were studied in $Pb(Y_{2/3}W_{1/3})O_3-Pb(Zr,Ti)O_3$(PYW-PZT) ceramics by using the constant current method. Young s modulus $Y_0^E$ and mechanical quality factor $Q_m$ are a function of the square of effective vibration velocity \upsilon_0$. The nonlinear proportional constants of the above functions indicate the degree of stability under the vibration level change. The stability of PYW-PZT ceramics estimated by these constants coincides with the results obtained through the heat generation. It was found that $Q_m$ was markedly decreased with increasing the vibration velocity, accompanying a lot of heat generation. The vibration hysteresis and dielectric loss according to the vibration velocity was reduced by doping $Fe_2O_3$to the ceramics. On the contrary, these losses was increased by doping $Nb_2O_5$.

• Journal of the Korean Chemical Society
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• v.39 no.4
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• pp.281-287
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• 1995

Copper(Ⅱ) complexes with N,N'-oxalylbis(salicylaldehydehydrazone), N,N'-malonylbis(salicylaldehydehydrazone) and N,N'-succinylbis(salicylaldehydehydrazone) have been prepared in 95% DMF. Their protonation and stability constants were investigated by potentiometric titration. We observed that MBSH ligand showed the largest protonation constant. The values of the protonation constants among three different ligands were increased as following order SBSH < OBSH < MBSH. However, the increasing order of stability constants was somewhat different such as Cu(Ⅱ)-SBSH < Cu(Ⅱ)-MBSH < Cu(Ⅱ)-OBSH. In addition, thermodynamic parameters, ΔH and ΔS of Cu(Ⅱ) complexes have been studied. As a result, we found the SBSH ligand produced the best stable copper (Ⅱ) complex.

• Elastomers and Composites
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• v.40 no.1
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• pp.53-58
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• 2005

Carbon tetrachloride is very reactive chain transfer agent due to the resonance stability of the trichlorocarbon radicals after breaking of C-Cl bond. Effect of benzylic radical comparing to trichlorocarbon radicals in the chain tranrfer reactions was investigated. From the structural point of view, cumyl chloride is a good candidate because it has the C-Cl bond with benzylic radicals after displacement of C-Ci bond. The reactivity of free radical polymerization of styrene in the presence of cumyl chloride was compared with that of carbon tetrachloride by calculating chain transfer constants. Results show that the cumyl chloride acts as a stronger chain transfer agent than carbon tetrachloride. The calculated chain transfer constant of cumyl chloride shows higher value (0.0463) than that of carbon tetrachloride (0.0011) in the styrene polymerization. High reactivity of cumyl chloride comparing to that of carbon tetrachloride is probably due to the higher resonance stability or benzylic radical than that or trichlorocarbon radicals after breaking of C-Cl bond. Monte Carlo simulation method is applied for characterizing the validity of kinetic constants according to the ratio of chain transfer agent to monomer.

• Journal of Pharmaceutical Investigation
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• v.30 no.4
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• pp.267-271
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• 2000

The effect of cyclodextrins on the solubility and stability of aspalatone (acetylsalicylic acid maltol ester, AM, CAS 147249-33-0), which has been recently found to have an antithrombotic effect, was investigated. The addition of ${\beta}-cyclodextrin\;({\beta}-CD),\;dimethyl-{\beta}-cyclodextrin\;(DMCD)\;or\;2-hydroxypropyl-{\beta}-cyclodextrin\;(HPCD)$ to the aqueous solution increased the solubility of AM concentration-dependently. From the phase solubility diagram, stability constants for $AM-{\beta}-CD$, -DMCD or -HPCD complexes were calculated to be 43.1, 78.3 and $53.0\;M^{-1}$. The addition of ${\beta}-CD$, DMCD or HPCD to AM solution retarded the degradation rate of AM in the acidic region. However, ${\beta}-CD$ and HPCD rather acted as an accelerator of degradation in the neutral and alkaline regions. DMCD had a stabilizing effect at all pHs studied.