• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.3001-3004
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• 2014

A series of hydroxyl-derivatized quaternized polymers were successfully synthesized by atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry), followed by quaternization reactions. ATRP was employed to synthesize poly(2-hydroxyethyl methacrylate) (PHEMA), followed by introduction of alkyne groups using pentynoic acid, leading to HEMA-Alkyne. 2-Azido-1-ethanol and 3-azido-1-propanol were combined with the HEMA-Alkyne backbone via click reaction, resulting in triazole-ring containing hydroxyl-derivatized polymers. Quaternization reactions with methyl iodide were conducted on the triazole ring of each polymer. Molecular weight, molecular weight distribution, and the degree of quaternization (DQ) were determined by gel permeation chromatography (GPC) and $^1H$ NMR spectroscopy. The average molecular weight ($M_n$) of the resulting polymers ranged from $5.9{\times}10^4$ to $1.05{\times}10^5g/mol$ depending on the molecular architecture. The molecular weight distribution was low ($M_w/M_n$ = 1.26-1.38). The transmission spectra of the 0.1 wt % aqueous solutions of the resulting quaternized polymers at 650 nm were measured as a function of temperature. Results showed that the upper critical solution temperature (UCST) could be finely controlled by the level of DQ.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.229-238
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• 2011

A series of novel glucose derived benzyl and alkyl 1,2,3-triazoles and their hydrochlorides have been synthesized via Cu(I)-catalyzed 1,3-dipolar cycloaddition. All the new compounds were characterized by MS, IR and NMR spectra. The DEPT, APT, $^1H$-$^1H$ and $^1H-^{13}C$ 2D NMR spectra for some compounds were also recorded. These compounds were evaluated for their in vitro antibacterial activities against Staphylococcus aureus ATCC 29213, Bacillus subtilis, Bacillus proteus, Pseudomonas aeruginosa, Escherichia coli ATCC 25922, and antifungal activities against Candida albicans and Aspergillus fumigatus. The bioactive data revealed that (3R,4S,5S,6S)-2-(hydroxymethyl)-6-methoxy-4,5-bis((1-octyl-1H-1,2,3-triazol-4-yl)methoxy)-tetrahydro-2H-pyran-3-ol 8a exhibited excellent antifungal activity against A. fumigatus with an MIC value of 0.055 mM compared to Fluconazole. It also showed broad inhibitory efficacy against tested bacterial strains with MIC values ranging from 0.049 mM to 0.39 mM.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1378-1382
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• 2013

We have investigated the complex forming behavior of cucurbit[6]urils(CB6) and cucurbit[7]urils(CB7) with 7-diethylamino-4-methylcoumarin(C460) in water. The electronic absorption maximum of C460 shows bathochromic shift with the addition of CB7 and fluorescence intensity is greatly increased, while CB6 has no noticeable effects on the spectroscopic properties of C460. It is noted that CB7 interacts more strongly with C460 than CB6 does. Fluorescence lifetime also significantly increased for the CB7 complex, which is attributed to reduced polarity surrounding C460 and/or C460 being in a restricted environment. The stoichiometry for the complex formation determined from the fluorescence titration measurement indicates that 2:1 complex in which two CB7 molecules bind to C460 is formed. Thus, two step equilibrium processes are suggested for the complex formation and the binding constants are estimated. The semi-empirical electronic structures calculations indicate that C460 is not included in the CB7 cavity but interacts noncovalently with the portal carbonyls of CB7.

• Journal of Biomedical Engineering Research
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• v.29 no.3
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• pp.231-238
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• 2008

Nelder-Mead downhill simplex method (DSM), a kind of deterministic optimization algorithms, has been used extensively for magnetoencephalography(MEG) dipolar source localization problems because it dose not require any functional differentiation. Like many other deterministic algorithms, however, it is very sensitive to the choice of initial positions and it can be easily trapped in local optima when being applied to complex inverse problems with multiple simultaneous sources. In this paper, some modifications have been made to make up for DSM's limitations and improve the accuracy of DSM. First of all, initial point determination method for DSM using magnetic fields on the sensor surface was proposed. Secondly, Univariant-DSM combined DSM with univariant method was proposed. To verify the performance of the proposed method, it was applied to simulated MEG data and practical MEG measurements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.7
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• pp.515-521
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• 2013

Magnetoelectric(ME) bulk composites with PZT-PNN-PZN/$Fe_2O_4$ were prepared by using a conventional ceramic methods and investigated on the ME voltage vs frequency of ac magnetic fields. We made the electric equivalent circuits by using the Maxwell-Wagner model and simulated the frequency dependence of ME voltage in low frequency region. ME devices were described by a series of two equivalent circuits of piezoelectric and magnetic, which have the relaxation time ${\tau}$ due to the interaction between ME device and load resistor. Equivalent circuit of piezoelectric material is independent of frequency. However ferrite magnetic materials have Debye absorption and dipolar dispersion, whose equivalent circuit is a function of frequency. Therefore we suggest the resistance in the equivalent circuit is proportion to $1+{\omega}^2{\tau}^2$ and the capacitance is in inverse proportion to $1+{\omega}^2{\tau}^2$ in the magnetic materials.

• Polymer(Korea)
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• v.33 no.1
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• pp.67-71
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• 2009

The stitching method for the synthesis of $Fr\acute{e}chet$-type dendrimers was elaborated using click chemistry between an alkyne and an azide. The core building block, 4,4'-(3,5-bis(azidopropyloxy)benzyloxy)bisphenyl, was designed to serve as the azide functionalities for dendrimer growth via click reactions with the alkyne-dendrons. The synthetic strategy involved an 1,3-dipolar cycloaddition reaction between an azide and an alkyne-functionalized $Fr\acute{e}chet$-type dendrons in the presence of Cu(I) species which is known as the best example of click chemistry.

• Bulletin of the Korean Chemical Society
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• v.5 no.1
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• pp.44-49
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• 1984

The ionic association constant (K) of N-methyl pyridinium iodide (NMPI) ion in several ethanol-water mixtures were determined by the combination of UV spectroscopy and conductance measurements using the Shedlovsky function as a correction factor. The measurement of electrical conductance and UV absorption were performed in 95, 90, 80 and 60 volume percentages of ethanol in the solvent mixture at 15, 25, 35 and 45 $({\pm}0.1)^{\circ}C$. The ion size parameter $(r_A+_D-)$ and the dipole moment $({\mu}_A+_D-)$ of NMPI ion were obtained from he linear plots of ln K vs. (1/D) and (D-1)/(2D+1), respectively. These ${\mu}_A+_D-$ values were in good agreement with the values of transition moment calculated from the equation, ${\mu}_{nm}=6.5168{\times}10^{-2}{\times}({\varepsilon}_{max}{\frac{\bar{\nu}_{\frac{1}{2}}}{\bar{\nu}_{max}})^{\frac{1}{2}}$ (Debye) which we have derived. The thermodynamic parameters indicate (1) that the water dipoles have an ordered rearrangement around the dipolar NMPI ions rather than the configuration existing in bulk free waters; and (2) that the equilibrium state between NMPI ion and its component ions are controlled by entropy.

• Bulletin of the Korean Chemical Society
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• v.4 no.2
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• pp.64-67
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• 1983

NMR shift arising from the electron orbital angular momentum and the electron spin dipolar-nuclear spin angular momentum interactions has been investigated for a $4d^{1}$ system in a strong crystal field of octahedral symmetry. To examine the NMR shif for a $4d^{1}$ system in a strong crystal field of octahedral symmetry, we derive a general expression for ${\Delta}$B/B using a nonmultipole expansion technique. From this expression all the multipolar terms are determined. For the $4d^{1}$ system in a strong crystal field of octahedral symmetry the exact solution for NMR shift, ${\Delta}$B, is compared with the multipolar results. ${\Delta}$B/B for the $4d^{1}$ system is also compared with that for the $3d^{1}$ system. It is found that the $1/R^{7}$ term contributes dominantly to the NMR shift. However, there is good agreement between the nonmultipole and multipolar results for R-values larger than 0.2 nm for the $4d^{1}$ system but for R-values larger than 0.4 nm for the $3d^{1}$ system.

• Bulletin of the Korean Chemical Society
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• v.7 no.2
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• pp.89-96
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• 1986

The NMR chemical shift arising from 4d electron angular momentum and 4d electron spin dipolar-nuclear spin angular momentum interaction for a $4d^1$ system in a strong crystal field of octahedral symmetry, when the threefold axis is chosen as the quantization axis, has been investigated. A general expression using a nonmultipole expansion method is derived for the NMR chemical shift. From this expression all the multipolar terms are determined. We find that the nonmultipolar results for the NMR chemical shift ${\Delta}B$, is exactly in agreement with the multipolar results when $R {\ge} 0.20$ nm. It is also found that the 1/$R^7$ term contributes to the NMR chemical shift almost the same as the 1/$R^5$ in magnitude. The temperature dependence analysis of ${\Delta}B$/B(ppm) at various values of R shows that the 1/$T^2$ term has the dominant contribution to the NMR chemical shift but the contributions of other two terms are certainly significant for a $4d^1$ system in a strong crystal field of octahedral symmetry when the threefold axis is chosen to be the axis of quantization.

• Bulletin of the Korean Chemical Society
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• v.14 no.1
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• pp.21-29
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• 1993

For the study of relaxation processes in complex spin system, a general master equation, which can be used to simulate a vast range of pulse experiments, has been formulated using the Liouville representation of quantum mechanics. The state of a nonequilibrium spin system in magnetic field is described by a density vector in Liouville space and the time evolution of the system is followed by the application of a linear master operator to the density vector in this Liouville space. In this master equation the nuclear spin relaxation due to intramolecular dipolar interaction or randomly fluctuating field interaction is explicitly implemented as a relaxation supermatrix for a strong coupled two-spin (1/2) system. The whole dynamic information inherent in the spin system is thus contained in the density vector and the master operator. The radiofrequency pulses are applied in the same space by corresponding unitary rotational supertransformations of the density vector. If the resulting FID is analytically Fourier transformed, it is possible to represent the final nonstationary spectrum using a frequency dependent spectral vector and intensity determining shape vector. The overall algorithm including relaxation interactions is then translated into an ANSIFORTRAN computer program, which can simulate a variety of two dimensional spectra. Furthermore a new strategy is tested by simulation of multiple quantum signals to differentiate the two relaxation interaction types.