• Polymer(Korea)
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• v.25 no.6
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• pp.759-764
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• 2001

In order to obtain PEO with reduced crystallinity, novel PEO derivatives containing carbonate linkages in the main chain have been synthesized by the reaction of various molecular weight poly (ethylene glycol)s (PEGs) with dimethyl carbonate (DMC) in the presence of $H_2SO_4$ to yield methyl carbonate terminated PEGs, followed by condensation reaction under vacuum in the presence of titanium isopropoxide (TiP) catalyst. The number average molecular weight of PEGs used was in the range of 200 and 600 g/mol. The structure and compositions of the resulting polymers were characterized by $^1$H-NMR and $^{13}C-NMR$. Their thermal behavior and molecular weight were characterized by DSC/TGA and GPC, respectively.

• Journal of the Korean Chemical Society
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• v.28 no.4
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• pp.205-209
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• 1984

The crystal and molecular structure of thiosinamine, $H_2NCSNHCH_2CHCH_2$, has been determined by X-ray diffraction method. The crystals are monoclinic, space group $P2_1/a$ with four molecules in a unit cell of dimensions, a = 9.819(3), b = 8.553(3), c = 9.170(2)${\AA}$, ${\beta}$ = 127.3(1)$^{\circ}$, and z = 4. Intensity data for 814 reflections were collected with a Rigaku-Denki automatic four circle diffractometer. The structure was solved by direct and Fourier methods. Refinements were carried out by full matrix least-squares method to a final R value of 0.046. The thiourea unit is planar, and the bond lengths and angles in that unit agree well with those in the compounds which contain a thiourea moiety. The molecules are linked together by the two patterns of N-H${\cdots}$S hydrogen bonds along the b-axis.

• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.506-510
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• 2007

Vacuum deposited 4,4',4''-tris(N-(1-naphthyl)-N-phenylamino)-triphenylamine (1-TNATA), a widely-used semiconductor material, is placed as a thin interlayer between indium tin oxide (ITO) electrode and a hole transporting layer (HTL) in OLEDs and a well-stacked 1-TNATA layer leads to stable and high efficiency devices by reducing the carrier injection barrier at the interface between the ITO anode and hole transport layers. According to Raman spectra, thermal annealing after deposition as well as electromagnetic field treatment during deposition lead to closer stacking of 1-TNATA molecules and resulted in molecular ordering. By thermal annealing at about $110^{\circ}C$, an increase in current flow through the film by over 25% was observed. Molecularly-ordered 1-TNATA films played an important role in achieving higher luminance efficiency as well as higher power efficiency of the multi-layered organic EL devices in the present work. Electromagnetic field treatment during deposition was less effective compared to thermal annealing

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.115-121
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• 1973

Crystalline products were obtained when$TiCl_4$ was reacted in dichloromethane with acetic, propionic, crotonic, benzoic, furoic and salicylic acids. Chemical analysis has shown that these were all dichlorodicarboxylatotitanium (IV). Cryoscopy of dichlorodipropionatotitanium (IV) indicated the carboxylato-complexes are dimeric. In the IR spectra of these complexes two strong bands both assigned to asymmetric carbonyl stretching vibration have been observed in the region$1500 - 1700cm^{-1}$ and the NMR spectrum of dichlorodipropionatotitanium (IV) has also shown two triplets and two quartets, which indicate that there are two chemically unequivalent carboxylato-ligands in the dimer $[TiCl_2(OOCR)_2]_2$. Their molecular structure was proposed to be bis-carboxo-bridged dimer.

• Journal of the Korean Chemical Society
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• v.55 no.2
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• pp.199-203
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• 2011

The title one-dimensional hydrogen-bonded coordination compound $[Cu^{II}(C_{13}H_{17}N_3OBr)(C_8H_5O_4)]{\cdot}2H_2O.CH_3OH$ has been synthesized and characterized by single crystal X-ray diffraction study. The monomeric unit contains a square-planar $Cu^{II}$ centre. The four coordination sites are occupied by a tridentate anionic Schiff base ligand (4-bromo-2-[(2-piperazin-1-yl-ethylimino)-methyl]-phenol) which furnishes an $N_2O$-donor set, with the fourth position being occupied by the oxygen atom of an adjacent terephthalate unit. Two adjacent neutral molecules are linked through intermolecular N-H---O and O-H---N hydrogen bonds and generate a dimeric pair. Each dimeric pair is connected with each other via discrete water and methanol molecules by hydrogen bonding to form a one-dimensional supramolecular network.

• Journal of the Korean Chemical Society
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• v.19 no.2
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• pp.85-91
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• 1975

The crystal structure of piperidinothiosemicarbazide, $C_6H_{13}N_3S$, has been determined by single crystal X-ray analysis. The space group is P21/c with four molecules in the unit cell of dimensions $a=14.68{\pm}0.04,\;b=4.59{\pm}0.02,\;c=12.92{\pm}0.04{\AA}\;and\;{\beta}=109.4{\pm}0.2^{\circ}$. Three-dimensional photographic intensities were estimated visually. The structure has been solved by an interpretation of a Patterson synthesis and refined by block-diagonal least-squares methods to give a final R value of 0.14 for 378 observed independent reflections. There are two independent hydrogen bonds in the structure. One of them is of the type N-H${\ldots}$S with the length 3.28 and $3.39{\AA}$, and another is of the type N-H${\ldots}$N with the length $3.03{\AA}$. Apart from the hydrogen bonding system the molecules are held together in the crystal by van der Waals forces.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.29-36
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• 1990

Cholesteryl pentyl carbonate $(C_{33}H_{56}O_3)$ is monoclinic, space group P21, with a = 12.484(3), b = 9.043(3), c = 14.053(3)$\AA$, ${\beta} = 94.12(2)^{\circ}$ and z = 2. The intensity data were measured for the 2969 reflections within sin $\theta/\lambda = 0.52 {\AA}^{-1}$, using an automatic four--circle diffractometer and graphite monochromated Mo-K$\alpha$ radiation. The atomic coordinates from cholesteryl octanoate were used in an initial trial structure and the structure was refined by full-matrix least squares methods. The final R-factor was 0.12 for 1164 observed reflections. The pentyl group has shortened bond lengths due to the high thermal vibrations in this region. Adjacent molecules are related by $2_1$ screw axis so that they are arranged in an antiparallel array, corresponding to the Monolayer Type II packing mode. There are close packings of cholesteryl groups within the monolayers. This packing type is similar to those of cholesteryl hexanoate, octanoate, hexyl carbonate and oleate.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.1
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• pp.28-37
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• 2022

The burning rate estimation method of solid propellants, based on closed bomb tests, has been introduced. The composition of the combustion gas is determined by using CEA and the Noble-Abel equation of state for high pressure operation conditions. Covolume taking into account the collision among molecules due to the actual volume of the molecule is modeled by LJ potential. A cubic form function is applied to calculate the volume change of propellant grains during combustion. The estimated burning rates of five different grain configuation at high pressure are fairly compared with BRLCB results within the maximum error of 6%.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.194-200
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• 2006

Self-assembled InAs/InAl(Ga)As quantum dots (QDs) were grown on InP substrates by a molecular-beam epiaxy, and their structural and optical properties were investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), and room-temperature photoluminescence (PL). AFM images indicated that the InAs quantum structures showed various shapes such as quantum dashes, asymmetric and symmetric QDs mainly caused by the initial surface conditions of InAl(Ga)As with the intrinsic phase separation. For the buried InAs QDs in an InAlGaAs matrix, the average lateral size and height of QDs were 23 and 2 nm, respectively. By changing the growth conditions for the QD samples, the emission wavelength of $1.55{\mu}m$ was obtained, which is one of the wavelength windows for fiber optic communications.

• Polymer(Korea)
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• v.30 no.4
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• pp.362-366
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• 2006

It was found by polarized FTIR spectroscopic studies that pentacene molecules are arranged with their molecular axes perpendicular to the substrate surface when pentacene films are deposited on a polyimide alignment layer. The ring plane in a pentacene molecule is arranged parallel to the rubbing direction of the polyimide alignment film while no specific arrangement of vertically deposited pentacene molecules was found for the film without rubbing. The pentacene band at $1296cm^{-1}$ which has a transition dipole moment parallel to the ring plane is much stronger in a polarized IR spectrum of parallel to the rubbing direction, whereas the band at $908cm^{-1}$ whose transition dipole align normal to the ring plane shows much stronger intensity in a spectrum of perpendicular to the rubbing direction. These findings indicate that orientation of polyimide chains affects the arrangement of pentacene molecules when they are deposited on a polyimide alignment film.