• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.305-305
• /
• 2006

The molecular structure and dynamics of inclusion compounds (ICs) consisting of n-perfluoroalkane (PFA) guests and ${\Box}-cyclodextrin$ (${\Box}-CD$) host were investigated using $^{19}F$ magic angle spinning (MAS) and $^{1}H{\to}^{19}F$ cross polarization (CP) / MAS NMR spectroscopy with the aid of thermal analyses, FT-IR spectroscopy, X-ray diffraction, and $^{1}H{\to}^{19}F$ CP/MAS technique revealed that $C_{9}F_{20}$ molecules included in ${\Box}-CD$ undergo vigorous molecular motion and partly come out of the ${\Box}-CD$ channel above $80^{\circ}C$. In case of $C_{20}F_{42}/{\Box}-CD$, an exothermic peak is observed by differential scanning calorimetry (DSC) at ca. $40^{\circ}C$ which suggests that ${\Box}-CD$ molecules become mobile and commence rearrangements that form more ordered structures at higher temperatures.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.1
• /
• pp.12-14
• /
• 1994

p-Fluorophenyl bicyclo[3.2.l]oct-6-en-2-yl cation (3) prepared in $FSO_3H-SO_2-CIF$ solution at -90$^{\circ}$C and examined by fluorine-19 nmr spectroscopy. The nmr data give a clear evidence for the formation of a stabilized ${\pi}$-bridging cation species in superacids. The degree of ${\pi}$delocalization in this cation is found to be inferior to the onset of nonclassical stabilization in 2-norbornenyl cation.

• Journal of the Korean Chemical Society
• /
• v.29 no.3
• /
• pp.213-219
• /
• 1985

The relative stability as a function of geometry in rigid cyclopropylcarbinyl cations was examined by $^{19}$F-nmr spectroscopy. 8-p-Fluorophenyl-tricyclo[3.3.1.0$^{2,7}$]octane-8-yl-(I), 9-p-fluorophenyl-tricyclo[3.3.1.0$^{2,8}$]nonane-9-yl (II), and 10-p-fluorophenyl-tricyclo[4.3.1.0$^{2,9}$]decane-10-yl cation(Ⅲ) were prepared from the corresponding carbinols in FSO$_3$H-SO$_2$ClF solution at -120$^{\circ}C$. $^{19}$F-nmr data indicate that the symmetrical bisected geometry of cyclopropane ring for ${\sigma}$-conjugation is a very impotant factor in charge delocalization. However, varied orientation of the bond angle ${\theta}$ within the bisected conformation does not affect the charge delocalization into the cyclopropane ring.

• Bulletin of the Korean Chemical Society
• /
• v.8 no.3
• /
• pp.144-145
• /
• 1987

The relative stability as function of geometry in the rigid tricyclopropylcarbinyl cations with varied bond angle (${\alpha}$) between the plane of cyclopropane ring and the bond connecting cyclopropane ring to cationic carbon was examined by $^{19}F$ nmr spectroscopy. 7-p-Fluorophenyltricyclo[2.2.2.$0^{2,6}$]octan-7-yl(4) and 8-p-fluorophenyltricyclo[3.2.2.$0^{2,7}$]nonan-8-yl cation (8) were generated from corresponding tertiary alcohols under stable ion conditions, and their $^{19}F$ chemical shifts were compared with those of model compounds such as 7-nortricyclyl cation (3) and tricyclo[3.3.1.$0^{2,7}$]octan-8-yl cation (7). Consequently, it is concluded that the varied orientation of bond angle (${\alpha}$) within in the bisected conformation does not affect degree of the charge delocalization into cyclopropane ring.

• Journal of Magnetics
• /
• v.21 no.4
• /
• pp.599-602
• /
• 2016

Fluoride (F) is an important element for the mineralization of body tissues. The purpose of this study was to administer fluoride prenatally to rats to evaluate its beneficial concentration for rat bone using microstructural analysis, to analyze its effect on the bone structure, and to evaluate the effect of its transfer through rat placenta. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectrometry (NMR) were performed. The $^{19}F$ NMR and $^{31}P$ NMR signals suggested the existence of fluoride ions in the apatite lattice because the signals were caused by the fluoride ions that were coupled to the phosphate atoms and were affected in the phosphate phases other than the element phases in the apatite. Consequently, if it was not affected too much, the desirable concentration of prenatal fluoride treatment could have a helpful effect on the bone crystal structure through placental fluoride transfer.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.7
• /
• pp.2345-2350
• /
• 2011

Variable temperature high-resolution $^{19}F$ magic angle spinning (MAS) solid-state NMR spectroscopy was used to characterize fluorocarbon (FKM) rubbers. The high-resolution spectra of copolymers made from two monomers, vinylidene fluoride and hexafluoropropene, and terpolymers composed of vinylidene fluoride, hexafluoropropene, and tetrafluoroethylene, were obtained using MAS speeds of up to 18 kHz combined with high temperatures of up to 200 $^{\circ}C$ at a magnetic field strength of 9.4 Tesla. From these high resolution solid-state NMR spectra, we were able to assign the spectral peaks and differentiate the copolymer FKM from the terpolymer FKM. We also determined quantitatively the monomer compositions of each FKM rubber.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.12
• /
• pp.2499-2501
• /
• 2008

• Journal of the Korean Magnetic Resonance Society
• /
• v.17 no.2
• /
• pp.81-85
• /
• 2013

Various fluorine-containing materials are used in electronic devices like LCD display panels and Li-ion batteries. The structural conformation of fluorine in fluorinated materials is an important contributing factor that influences the chemical and physical properties. The conformation can be changed by heat and stress during manufacture or use. Understanding the conformational changes is critical for understanding the performance and durability of electronic devices. Solid-state NMR spectroscopy could be widely used for the analysis of various fluorine-containing materials for electronic devices. However, conventional CPMAS probes cannot be used for in-situ analysis of fluorine-containing electronic devices like LCD panels and Li-ion batteries. In this paper, we show the design, construction, and optimization of a $^{19}F-^{13}C$ double-resonance solid-state NMR probe for a 400MHz wide-bore magnet with a flat square coil for in-situ analysis of fluorine-containing electronic devices without observing fluorine background signals. This custom-built probe does not show any fluorine background signals, and can have higher efficiency for lossy samples.

• Bulletin of the Korean Chemical Society
• /
• v.3 no.2
• /
• pp.66-70
• /
• 1982

The question of the bicyclohomoaromatic stabilization and destabilization is examined. The chemistry of bicyclo(3.2.1)octa-3,6-dienide anion has been studied on order to test these concepts. The bicyclooctadienide anion is shown to be stable delocalized ion which undergoes a facile proton-deuterium exchange reaction. The solvolysis of bicyclo(3.2.1)octa-3,6-dienyl p-nitrobenzoate is much slower than the monoene analog. We have made direct observation of the bicyclooctadienyl and octenyl cations by $^{19}F$-nmr spectroscopy, and were able to demonstrate that the bicyclooctadienyl cation was bishomoantiaromatic.

• Polymer(Korea)
• /
• v.27 no.3
• /
• pp.176-182
• /
• 2003

The fluorine-containing epoxy resin, 2-trifluorotoluene diglycidylether (FER) was prepared by reaction of 2-chloro-${\alpha}$,${\alpha}$,${\alpha}$-trifluorotoluene with glycerol diglycidylether in the presence of pyridine catalyst. Curing behavior of FER/DDM system was investigated using dynamic and isothermal DSC. Cure activation energy (Ea) was determined by Flynn-Wall-Ozawa's equation. The rheological properties of FER/DDM system were studied under isothermal condition using a rheometer. Cross-linking activation energy (Ec) was determined from the Arrhenius equation based on gel time and curing temperature. As a result, the chemical structure of FER was confirmed by FT-IR, $\^$13/C NMR, and $\^$19/F NMR spectroscopy. The cure activation energy of FER/DDM system was 55.4 kJ/mol and conversion and conversion rate were increased with the curing temperature. The cross-linking activation energy of FER/DDM system was 41.6 kJ/mol and gel time was decreased with the curing temperature.