• Journal of the Korean Chemical Society
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• v.65 no.5
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• pp.320-326
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• 2021

This study investigated the effect of the structure of the crosslinking agent used in contact lens polymerization on the physical properties and drug dissolution of contact lenses.es Contact lenses were manufactured using 0.3% and 3% of 4 types of crosslinking agents, respectively, and ofloxacin was used as the drug. Contact lenses using hydrophilic crosslinking agents improved water contents and wettability, and the more hydrophilic functional groups, the greater the effect. Contact lenses with a high concentration of crosslinking agent had a low concentration of eluted drug and a longer release time. The cross-linking agent structure of contact lenses had an effect on improving the performance of contact lenses and controlling drug release.

• Applied Chemistry for Engineering
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• v.20 no.5
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• pp.536-541
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• 2009

Plasma-polymerized acrylic acid films were deposited on Si wafer and KBr pellet by remote plasma-enhanced chemical vapor deposition (PECVD). Effects of plasma power, reaction pressure, indirect plasma method on the growth rate, chemical structure, and chemical bonding state of the films were investigated. Chemical structure and chemical state of the films were characterized by Fourier transformed infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis and curve fitting technique. Growth rate of the film increased to a saturation value with plasma power of 100 W, but showed the maximum with reaction pressure at 300 mtorr. Whenever W/FM factor (applied energy per gas molecule) increased by increasing plasma power or lowering pressure, the fragmentation of acrylic acid molecules was promoted. From the XPS curve fitting analyses, we found that the intensity of carboxyl COO bonding peak decreased with W/FM factor, and the tendency of intensity change of carboxylic COO peak was contrary to those of ether C-O and carbonyl C=O peaks.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.2
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• pp.133-139
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• 2018

Chemically damaged hair is vulnerable to external stimuli in daily life due to the weakened physical properties of the hair strand itself. The purpose of this work was to determine whether chemical conjugation between hair keratin proteins restores tensile strength and thus results inpreventing further deterioration under repeated combing. A model damaged hair tress was produced by a typical perm-process. Then, it was internally crosslinked by the bifunctional crosslinker (3-aminopropyl)triethoxysilane (APTES), via both silane coupling and carbodiimide chemistry. Physical properties, including tensile strength, Young's modulus, and plateau stress, were measured to verify the effect of internal crosslinking, and the existence of crosslinking was verified by Fourier transform infrared (FT-IR) spectroscopy. The degrees of hair breakage and split ends were evaluated by repeated combing-drying tests. Physical properties of chemically damaged hair were restored by internal crosslinking. Successful crosslinking of APTES via both silane coupling and carbodiimide chemistry was verified by FT-IR spectra. Prevention of breakage and split ends after repeated combing with heat was observed. Human hair can be weakened by chemical damage including perm-processing, so restoring such properties is a major issue in the hair care industry. This work shows that internal crosslinking of damaged hair via chemical conjugation would be a potent method to restore the healthy hair.

• Restorative Dentistry and Endodontics
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• v.32 no.3
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• pp.169-179
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• 2007

This study was to compare the microshear bond strength $({\mu}SBS)$ of light- and chemically cured composites to enamel coupled with four 2-step self-etch adhesives and also to evaluate the incompatibility between 2-step self-etch adhesives and chemically cured composite resin. Crown segments of extracted human molars were cut mesiodistally, and a 1 mm thickness of specimen was made. They were assigned to four groups by adhesives used: SE group (Clearfil SE Bond) AdheSE group (AdheSE), Tyrian group (Tyrian SPE/One-Step Plus), and Contax group (Contax) Each adhesive was applied to a cut enamel surface as per the manufacturer's instruction. Light-cured (Filtek Z250) or chemically cured composite (Luxacore Smartmix Dual) was bonded to the enamel of each specimen using a Tygon tube. After storage in distilled water for 24 hours, the bonded specimens were subjected to ${\mu}SBS$ testing with a crosshead speed of 1 mm/minute. The mean ${\mu}SBS$ (n=20 for each group) was statistically compared using two-way ANOVA, Tukey HSD, and t test at 95% level. Also the interface of enamel and composite was evaluated under FE-SEM. The results of this study were as follows ; 1. The ${\mu}SBS$ of the SE Bond group to the enamel was significantly higher than that of the AdheSE group, the Tyrian group, and the Contax group in both the light-cured and the chemically cured composite resin (p < 0.05). 2. There was not a significant difference among the hdheSE group, the Tyrian group, and the Contax group in both the light-cured and the chemically cured composite resin. 3. The ${\mu}SBS$ of the light-cured composite resin was significantly higher than that of the chemically cured composite resin when same adhesive was applied to the enamel (p < 0.05). 4. The interface of enamel and all 2-step self-etch adhesives showed close adaptation, and so the incompatibility of the chemically cured composite resin did not show.

• Journal of the Korean Chemical Society
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• v.46 no.1
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• pp.90-96
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• 2002

The STS contents, emphasized in the 6th curriculum, in the chemistry textbooks(II) were analyzed. The STS contents in textbooks showed average value of 2.7%. The chapter of ‘chemical bond and compound' were included 3.8% of STS contents. And the chapter of ‘atomic structure and periodic table', ‘state of material and solution', ‘science of material', and ‘chemical reaction' contained 3.2%, 2.2%, 1.9%, and 1.9% of STS contents, respectively. When the STS contents were analyzed by STS topics of Piel, the results are as follows; 33.7% on effect of technological developments, 27.5% on environmental quality and utilization of natural source, 19.6% on human engineering, 13.8% on energy, and 5.4% on sociality of science. However, there were no topics on population, space research and national defense. When the STS contents were analyzed by student activities of SATIS, most of the activities were research and case study. There were few field activities of practical investigation, problem solving and decision making, research design and stimulation. There were no activities of role play.

• The korean journal of orthodontics
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• v.27 no.5 s.64
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• pp.781-789
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• 1997

The purpose of this study was to evaluate the effects of fluoride relasing orthodontic sealant on the shear bond strength of light-and chemical-cured orthodontic rosins, to compare the shear bond strenth with light-and chemical-cured orthodontic resins, and to identify the changes of shear bond strength by rebonding in vitro. The brackets were divided into eight groups. Each group of metal brackets had different bonding mechanisms with adhesives. Group A : Transbond only Group B : Mono-Lok 2 only Group C : Light cured FluoroBond+Transbond Group D : Light cured FluoroBond+Mono-Lok 2 Group E : Transbond only(rebonded) Group F : Nomo-Lok 2 only(rebonded) Group G : Light cured FluoroBond+Transbond(rebonded) Group H : Light cured FluoroBond+Mono-Lok 2(rebonded) 65 extracted human premolars were prepared for bonding and 65 metal brackets for each group were bonded to prepared enamel surfaces of buccal surfaces as the above prescription. 24 hours bonding after, the Instron universal testing machine was used to test the shear bond strength of metal brackets to enamel. After debonding, same kind of metal brackets for each group were rebonded to prepared enamel surfaces of buccal surfaces to test the shear bond strength at the rebonding to enamel. Statistical analysis of the data was carried out Student's t-test ANOVA test, and Scheffe test using $SPSS/PC^+$ The results were as follows : 1. The order of shear bond strength was Group B(11.84MPa), Group A(10.75MPa), Group, D(9.69MPa), and Group C(9.39MPa)in lst bonded groups. 2. The order of shear bond strength was Group E(7.40MPa), Group G(6.48MPa), Group F(5.89MPa), and Group H(5.15MPa) in rebonded groups. 3. The shear bond strength of chemical cured orthodontic rosins had higher than that of light-cured orthodontic resins in all groups, but there was no statistical significance between groups(P>0.05). 4. In rebonded groups, the shear bond strength of light cured orthodontic rosins had higher than that of chemical cured orthodontic resins, but there was no statistical significance between groups(P>0.05). 5. The shear bond strength of all rebonded groups progressively decreased than that of 1st bonded groups, and there was statistical significance between groups(p<0.05, p<0.001).

• Journal of the Korean Chemical Society
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• v.18 no.5
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• pp.341-353
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• 1974

The electrochemical reduction of triphenylphosphine penylimide in nonaqueous media has been examined by polarography, cyclic voltammetry, controlled-potential coulometry and electron spin resonance spectroscopy. The reduction of triphenylphosphine phenylimide proceeds by a one-electron transfer to form anion radical which undergoes both protonation and a second one-electron reduction followed by cleavage of the phosphorus-nitrogen double bond. Aniline is a major product. The cleavage of a phosphorus-phenyl bond was also observed after reduction of triphenylphosphine oxide which is one of the major products of the chemical reaction which follow the primary process.

• Journal of the Korean Chemical Society
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• v.60 no.5
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• pp.362-373
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• 2016

In this study, ionic compound in the science textbooks developed under the 2009 revised national curriculum were analyzed in terms of the scientific concept and model description and the student understanding through the questionnaires. Analysis of textbooks was performed for science2 of middle school and chemistry I & II of high school. Questionnaire was carried out with 194 students including middle school 2nd grade and high school 1st-3rd grade. The results are as follows: First, as a result of analysis of textbooks, scientific concepts and models used to explain the ionic compound showed differences depending on the types of textbooks. In addition, scientific models were provided with or without explanation for the scientific concepts. Second, analysis of the questionnaire showed that students didn’t properly understood scientific concepts and models in the ion formation, stoichiometric ratio between ions.

• Analytical Science and Technology
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• v.23 no.5
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• pp.505-510
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• 2010

When polybutadiene dissolved in toluene was a binder of carbon powder, the volatility of solvent just after electrode fabrication assured the mechanical solidity of the carbon paste electrode. This characteristic met the qualifications for practical use of carbon paste electrodes. A new enzyme electrode bound with butadiene rubber was constructed. In order to confirm whether it shows quantitative electrochemical behaviors or not, its electrochemical kinetic parameters, e.g. the symmetry factor, the exchange current density, the capacitance of double layer, the time constant, the maximum current, the Michaelis constant and other factors were investigated. These experimental facts showed that butadiene rubber is a recommendable binder for practical use of a carbon paste electrode.

• Korean Journal of Crystallography
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• v.14 no.1
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• pp.16-23
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• 2003

The electronic structure and chemical bonding of β-MnO₂ were theoretically investigated by DV-X/sub α/ (the discrete variation X/sub α/) method. which is a sort of the first principle molecular orbital method using Hatre-Fock-Slater approximation. The calculations on several cluster models having different sizes were carried out for the determination of a model suited for analyzing bulk state. The Mn/sub 15/O/sub 56/ model was selected as a sufficiently suitable model for the calculation of electronic state and chemical bonding by the comparison of the calculated XPS (X-ray photo-electron spectrum) and experimentally measured XPS. By using this model, the electron energy level, the density of state, the bond overlap population, the charge density distribution, and the net ionic transfer between cations and anions were calculated and discussed.