• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.2906-2910
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• 2014

This report introduces Gaussian electrostatic models (GEMs) to account for charge penetration effects in water-water interactions, allowing electrostatic interactions to be accurately described. Three different Gaussian electrostatic models, GEM-3S, GEM-5S, and GEM-6S are designed with s-type Gaussian functions. The coefficients and exponents of the Gaussian functions are optimized using the electrostatic potential (ESP) fitting procedure based on that of the MP2/aug-cc-pVTZ method. The electrostatic energies of ten different water dimers that were calculated with GEM-6S agree well with the results of symmetry-adapted perturbation theory (SAPT), indicating that this designed model can be effectively applied to future water models.

• Korean Journal of Food Science and Technology
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• v.24 no.1
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• pp.37-41
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• 1992

Starch solid system was used to investigate the effects of lipoxygenase, linoleic acid and water activity on the oxidation of ${\beta}-carotene$ or ${\alpha}-tocopherol$. ${\beta}-carotene$ or ${\alpha}-tocopherol$ was co-oxidized severely with linoleic acid by lipoxygenase, and these were reduced to 19% and 5% of initial concentration, respectively, after 2 days storage at $a_w$ 0.72 in the system. The concentration of ${\beta}-carotene$ and the destruction rates were linearly correlated. However, the ${\beta}-carotene$ was very stable in the system without linoleic acid and lipoxygenase. The oxidation products of ${\alpha}-tocopherol$ were considered as ${\alpha}-tocopheryl$ quinone and ${\alpha}-tocopheryl$ dimer, and the level of ${\alpha}-tocopherol$ quinone increased as the reaction time increased.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.11a
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• pp.83-83
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• 2000

Alkylketene dimer was known as a cellulose reactive or alkaline size because it does not require to fix to the fiber as do the traditional rosin sizes. A proposed sizing mechanism of AKD was the formation of P -ketoester bond between AKD and cellulose which provides the permanent attachment and the orientation of the hydrophobic alkylchains outward. However, some questions about the reaction had arisen and thus, the sizing mechanism of AKD has been a subject of controversy for several decades. The major concern of the controversy is that AKD is really reactive with cellulose or not in the papermaking conditions. In this study, reaction between AKD and pulp fiber was investigated, in order to find out whether AKD forms P-ketoester with pulp fiber during aging under no catalyzed neutral condition with obvious spectroscopic evidence. In addition, effect of aging treatment on the sizing development was studied. It has been disclosed that, in absence of water, AKD reacted with cellulose to form P -ketoester linkage under no catalyzed neutral condition, while, in presence of water, most of AKD was hydrolyzed to a dialkyl ketone or P -ketoacid. In addition, during the aging treatment of AKD-sized paper, its typical IR spectra bands gradually were reduced, completely disappeared after 6hr aging, and formed new absorption bands at 1707cm-' and shoulder peak at 1700cm-' which refer to the typical dialkylketone absorption bands. Therefore, the formation of P -ketoester between AKD and pulp fiber is impossible in the practical papermaking process. It could be suggested that the sizing development of AKD-sized paper is obtained by next two mechanism: 1) formation of a thin-layer of AKD on the fiber surface through melting and spreading of AKD emulsion particles by heat and 2) the hydrolysis of AKD to dialkyl ketone which has higher melting point, during drying and storage of AKD sized papers.

• Journal of the Korean Graphic Arts Communication Society
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• v.14 no.1
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• pp.17-29
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• 1996

N-substituted acrylamide hydrogel is reported to have the feature of bing transparent and sensitive enough to response to a temperature stimulus below the temperature of phase transition. Especially at the near of 35 C it becomes shrunk and opaque very quickly. It has also the characteristic of reversing swelling and shrinking. The experiment showed that it is possible to produce a functional gel of super water absorption with the process of free radical polymerizing PVA(polyvinylalcohol) and PAA(polyacrylamide), and crosslinking. The ratio of shrinking and swelling caused by copolymerization rises 10% to 80% at the each temperature of 20 C, 30 C, 40 C, respectively. Phase transition temperature of this gel by copolymerization is50 C while that of ordinary N-substituted acrylamides is between 32~35 C. This temperature reaches the rearing limit of animals and plants so that volumetric transition polymer gel can be ulilized in varying fields such as agriculture/gardening which are water-using field, on-off switch sensing temperature and volumetric variation, processing of liquid wastes and civil engineering works, architecture and electronics. We have no doubt that this material will be the high-functional resin in the hi-tech age of the near future.

• Mass Spectrometry Letters
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• v.12 no.3
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• pp.118-124
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• 2021

Many previous studies have focused on revealing the harmfulness of microplastic particles, whereas very few studies have focused on the effects of chemicals, particularly photooxidation product. In this study, products of photodegradation from expanded polystyrene (EPS), compounds produced by photolysis by ultraviolet (UV) light, were investigated. EPS was directly irradiated and photolyzed using a UV lamp, and then the extracted sample was analyzed using high-resolution mass spectrometry (HRMS). Multiple ionization techniques, including electrospray ionization, atmospheric pressure chemical ionization, and atmospheric pressure photoionization, were used. In total, >300 compounds were observed, among which polystyrene monomer, dimer, and oxidized products were observed. In this work, the data presented clearly demonstrate that it is necessary to identify and monitor oxidized plastic compounds and assess their effect on the environment.

• Journal of Korean Society on Water Environment
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• v.28 no.5
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• pp.669-675
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• 2012

Recently, there have been active researches regarding endocrine-disrupting chemicals (EDCs). In this study, fifteen small freshwater streams in Cholla-namdo province, South Korea were investigated with respect to the concentration of the endocrine disruptors - Bisphenol A (BPA), styrene monomer (SM), styrene dimer (SD), and styrene trimer (ST) by gas chromatography-mass spectrometry (GC-MS). Measured concentration of the target compounds in the sampled water ranged from

• Journal of the Korean Chemical Society
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• v.53 no.1
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• pp.7-16
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• 2009

The global minimum structures of the benzene-water, Bz-$H_2O$ and benzene-water cation complex, [Bz-$H_2O]^+$ have been investigated using ab initio and density functional theory(DFT) with very large basis sets. The highest levels of theory employed in this study are B3LYP/cc-pVQZ for geometry optimization and MP2/aug-cc-pVTZ//B3LYP/aug-cc-pVTZ for binding energy. The harmonic vibrational frequencies and IR intensities are also determined at the various levels of theory to confirm whether the structure of water complex is affected by the presence of benzene. The binding energies of Bz-$H_2O$ (N-1) structure are predicted to be 3.92 kcal/mol ($D_e$) and 3.11 kcal/mol ($D_0$) after the zero-point vibrational energy correction at the MP2/cc-pVQZ//B3LYP/cc-pVQZ level of theory. The binding energies of [Bz-$H_2O]^+$ (C-1) structure are predicted to be 9.06 kcal/mol for $D_e$ and 7.82 kcal/mol for $D_0$ at the same level of theory.

• Korean Journal of Food Science and Technology
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• v.31 no.4
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• pp.931-937
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• 1999

Styrene dimers and trimers from polystyrene cup noodle containers were analyzed by GC and GC/MS extracted with various simulants. For the quantitation of styrene dimers and trimers, 1,3-diphenylpropane (DP) and benzyln-butyl phthalate (BBP) were chosen as the standards. The results showed that the average of the styrene dimers in the containers was 603 ppm, and that of trimers was 5731 ppm. Four styrene dimers, including 1,2-diphenyl-cyclobutane, were identified as well as seven trimers such as 2,4,6-triphenyl-l-hexene. The migration of the styrene dimers and trimers, from the cup noodle containers of polystyrene into foods, was conducted using simulants including boiling water as well as soybean oil and n-heptane. In addition to, the analysis of each migrated styrene was also performed filled with boiling water into noodle and soup after certain time (5, 10, 20, 30 min). The results showed that the migration of styrene dimers and trimers from cup noodle containers was not detected in the case of using boiled water or soybean oil as a simulant, while styrene dimers and trimers were detected 1.18 ppm and 14.21 ppm, respectively, when heptane was adopted as a simulant. In the case of filling with boiled water into noodle and soup, both styrenes were not detected at 5 min and 10 min, however, some samples standing for 20 min released styrene dimers and trimers as much as 0.009 ppm, and 0.019 ppm for 30 min.

• Journal of the Korean Wood Science and Technology
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• v.27 no.1
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• pp.79-87
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• 1999

To use the agricultural residues as the raw material of molded packaging material, the packaging trays were manufactured from rice-straw pulp. The physical properties were measured to compare non-treated trays with the addition trays, such as the addition of starch, rosin size, carboxymethyl cellulose(CMC), polyethylene glycol(PEG), alkylketene dimer(AKD), polyacryl amide(PAM). The results were as follows : 1. In the addition of starch, air permeability at addition of 5% was highest. Bursting strength and tensile strength were smaller than non-treated trays. 2. In the addition of rosin size, air permeability, bursting strength and tensile strength were smaller than non-treated trays. 3. In the addition of CMC, air permeability was higher than non-treated trays. Bursting strength and tensile strength were similar to non-treated trays. 4. In the addition of PEG, air permeability was higher than non-treated trays. Bursting strength at addition of 3% was the highest and tensile strength was smaller than non-treated trays. 5. In the addition of AKD, air permeability at addition of 1% and 5% was higher than non-treated trays. Bursting strength and tensile strength were smaller than non-treated trays. 6. In the addition of PAM, air permeability at addition of 0.01% was the highest. Tensile strength at addition of 0.01% were higher than non-treated trays. 7. The water absorption of the trays decreased with increasing adding of natural additives.

• Journal of the Korean Chemical Society
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• v.59 no.2
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• pp.117-124
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• 2015

The DFT and ab initio calculations have been performed to elucidate hydrogen interaction of hydrogen polyoxide dimers, $H_2O_n-H_2O_m$ (n=1-4, m=1-4). The optimized geometries, harmonic vibrational frequencies, and binding energies are predicted at various levels of theory. The harmonic vibrational frequencies of the molecules considered in this study show all real numbers implying true minima. The higher-order correlation effect were discussed to compare MP2 result with CCSD(T) single point energy. The binding energies were corrected for the zero-point vibrational energy (ZPVE) and basis set superposition errors (BSSE). The largest binding energy predicted at the CCSD(T)/cc-pVTZ level of theory is 8.18 kcal/mol for $H_2O_4-H_2O_3$ and the binding energy of water dimer is predicted to be 3.00 kcal/mol.