• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1309-1338
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• 2002

The fluorescence and photoisomerization quantum yields of trans-1-(9-anthryl)-2-(4-pyridyl)ethene (t-4-APyE), 1-(10-methyl-9-anthryl)-2-(4-pyridyl)ethene (t-4-MeAPyE), and 1-(10-chloro-9-anthryl)-2-(4- pyridyl)ethene (t-4-ClAPyE) were measured in cyclohexane, acetonitrile, and methanol at room temperature.Polar solvents result in the drastic reduction of fluorescence quantum yield and increase of photoisomerization quantum yield for all three compounds. These results are probably due to the stabilization of intramolecular charge transfer (ICT) excited state in polar solvent. The higher contribution of ICT in the presence of more electron-donating methyl substituent, manifested by largest positive fluorescence solvatochromism, indicates that the pyridine ring acts as an electron acceptor. Protonation or methylation makes pyridine ring stronger electron acceptor and causes long-wavelength ground state charge transfer absorption band and complete quenching of fluorescence. The fluorescence from t-4-APyE derivatives can be switched off responding external stimuli viz. medium polarity, protonation, or methylation.

• Rapid Communication in Photoscience
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• v.3 no.4
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• pp.85-87
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• 2014

We studied the characteristics of emissive state of the first (p-G1) and second (p-G2) generation of phenylacetylene dendrimers bearing stilbene as a core by using time-resolved fluorescence spectroscopy in cyclohexane (c-Hex) and N, N-dimethylformide (DMF), which are nonpolar and polar solvents, respectively. Time-dependent red-shift of emission spectra p-G2 both in c-Hex and DMF was observed in comparison with p-G1. Besides, the time constant of red-shift of spectra was found to be larger in DMF than in c-Hex. This indicates that the emissive state of p-G2 has a polar character in DMF as a result of charge delocalization from core to peripheral dendrons followed by stabilization of emissive state.

• Journal of Photoscience
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• v.9 no.1
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• pp.29-32
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• 2002

The solvent effect in a series of polar and non-polar solvents of varying dielectric constants and refractive indices has been investigated by studying electronic spectra (S$_1$band) of a series of exalite laser dyes at room temperature (25$\pm$1$\^{C}$). These data are used to determine the magnitude ($\mu$$\_$e/) and direction ($\theta$) of the electric dipole moments in the first electronically excited state. The results indicate that the observed band systems in these compounds may be attributed to ←$\pi$ transition.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.577-583
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• 2011

Stabilized biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) were prepared by controlled coprecipitation method for hyperthermia application. ESR measurements determined that all of the interactions in the individual SPIONs (1 nm and 11 nm) were antiferromagnetic in nature because the ions contributed to the magnetization with a range of magnetic moments. In-situ monitoring of the temperature increment was performed, showing that the microwave absorption rate of the SPIONs was dispersed in an appropriate host media (polar or non-polar solvents) during microwave irradiation. Microwave absorption energy rates and heat loss of SPIONs in solvent were calculated by non-linear data fitting with an energy balance equation. The microwave absorption rates of SPIONs dispersed in solvent linearly increases when the concentration of SPIONs increases, implying that the microwave absorption rate can be tunable by changing the concentration of SPIONs.

• Macromolecular Research
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• v.13 no.1
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• pp.14-18
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• 2005

Under irradiation in a microwave oven, six novel poly(amide-imide)s containing tetrahydropyrimidinone, tetrahydro-2-thioxopyrimidine moieties and trimellitic rings in their main chains were synthesized through the polycondensation reaction of N,N'-(4,4'-diphenylether)bis(trimellitimide) diacid chloride with six different derivatives of tetrahydropyrimidinone and tetrahydro-2-thioxopyrimidine in the presence of a small amount of a polar organic medium, such as o-cresol. The polycondensation proceeded rapidly and completed within 7-9 min, producing a series of new poly(amide-imide)s in high yield that showed inherent viscosities in the range 0.33-0.52 dL/g. These poly(amide-imide)s were characterized by elemental analysis, viscosity measurement, thermal gravimetric analysis, solubility test, and FT-IR spectroscopy. All of the polymers were soluble at room temperature in polar solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, tetrahydrofuran, and N-methyl-2-pyrrolidone.

• Bulletin of the Korean Chemical Society
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• v.25 no.11
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• pp.1648-1652
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• 2004

A set of unprecedented syndiospecific dimethyl- and diethylamino-functionalized polystyrenes was prepared by catalytically polymerizing the corresponding monomers using (pentamethylcyclopentadienyl)titanatrane/MMAO catalytic system. Dialkylamino-functionalized styrene monomers were synthesized by Wittig reaction from the corresponding aldehyde in high yield. The resulting polymers are soluble in polar organic solvents such as THF and show good thermal stability. The chemical transformation of the syndiospecific poly(4-diethylaminostyrene) also gave new polar polymers, namely syndiotactic poly(4-diethylaminostyrene hydrochloride), which is unattainable by traditional synthetic methods.

• Macromolecular Research
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• v.12 no.3
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• pp.258-262
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• 2004

We have developed facile and rapid polycondensation reactions of N-trimellitylimido-L-leucine diacid chloride 1 with eight different derivatives of hydantoin compounds 2a-h, in the presence of a small amount of a polar organic medium, such as Ο-cresol, by using a domestic microwave oven. The polycondensation reactions proceeded rapidly-they were complete within 7-9 min-to produce a series of novel optically active poly(amide-imide)s (3a-h) in high yield with inherent viscosities of 0.33-0.51 dL/g. We characterized the resulting poly(amide-imide)s by elemental analysis, thermal gravimetric analysis (DSC, TGA, and DTG), and FTIR spectroscopy, and by measuring their viscosities, specific rotations, and solubilities. All of the polymers were soluble at room temperature in polar solvents such as N ,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, tetrahydrofuran, and N-methyl-2-pyrrolidone.

• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.434-437
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• 1991

Irradiation of 5-styryl-1,3-dimethyluracil (5-SDU) with 2,3-dimethyl-2-butene (DMB) gives a [4+2] cycloadduct which is converted into a [2+2] cycloadduct on the prolonged irradiation. Triplet sensitization, quenching, and external heavy atom effect on the [4+2] photocycloaddition reaction demonstrate the singlet pathway and salt effect excludes a radical ion pair precursor possibility. Polar solvents increase the reaction efficiency implying a polar exciplex involvement in the [4+2] photocycloaddition reaction. Inverse temperature dependence both on the reaction and DMB fluorescence quenching of 5-SDU indicates the presence of a singlet exciplex intermediate.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.123-124
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• 2006

Ionic liquids (ILs) are collecting keen interests as an advanced substituent of electrolyte solution as well as novel solvents. In the present talk, I will introduce some strategies to fix IL structure on polymer chains to prepare polar polymers with low glass transition temperature. Namely, cationic, anionic, and zwitterionic monomers have been prepared, and they have been homopolymerized or copolymerized to prepare polymer electrolytes with different properties. The polymers themselves showed very poor ionic conductivity, but it was improved by suitable spacer between charged site and main chain. Other unique characteristics of functional ILs and new polymerized ionic liquids will also be mentioned.

• Advances in Traditional Medicine
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• v.9 no.4
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• pp.335-338
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• 2009

Aerial parts of Sida rhombifolia Linn. (Malvaceae) were extracted successively using various solvents and screened for various parameters of antiarthritic activity such as adjuvant-induced arthritis, motor performance, and histopathological study. The ethanol and the aqueous extracts showed potent activity; further these extracts were fractionated by using column chromatography. The fraction ET1 isolated from ethanol extract showed the most potent antiarthritic activity.