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Mesogen 을 포함하지 않은 액정 polyurethane 의 합성과 열적성질에 관한 연구
이종백,최대웅 ( Jong Back Lee,Dae Woong Choi ) 한국공업화학회 1997 공업화학 Vol.8 No.2
액정 polyurethane은 DMF 용매중 1,4-bis(6-hydroxyhexoxy)benzene (BHB6)과 2,5-tolylene diisocyanate (2,5-TDI)를 중부가 반응에 의해서 합성하였다. 고유점도는 0.26, 0.42 ㎗/g였다. 생성된 polyurethane의 열적성질 및 구조확인은 DSC, 편광현미경, X-ray회절 그리고 ¹H-NMR 및 FT-IR에 의해 확인하였다. 특히 분자량이 서로 다른 polyurethane 2,5-TDI/BHB6의 열적성질 및 물성에 대해서 비교 검토하였다. 고유점도가 [η]=0.26인 polyurethane 2,5-TDI/BHB6는 monotropic 액정성을 나타내었다. 이러한 것은 구조적으로는 mesogen을 포함하고 있지 않다. 예를 들면 LCPU-L(저분자량)은 T_(I.LC)(등방성액체상전이점-액정) 및 T_(LC-k)(액정-결정)은 122℃부터 89℃까지 관찰되었다. Liquid crystalline polyurethanes were prepared from 1,4-bis(6-hydroxyhexoxy)benzene (BHB6) and 2,5-tolylene diisocyanate (2,5-TDI) solution polymerization in dimethylformamide produced intrinsic viscosities in the range 0.26 and 0.42 ㎗/g. The polyurethanes were investigated by DSC, Polarizing microscopy, X-ray, ¹H-NMR and IR spectroscopy. Polyurethanes of two different molecular weights were studied in detail and these will be referred to as low molecular weight and high molecular weight. Polyurethane 2,5-TDI/BHB6 with [η]=0.26 ㎗/g prepared from BHB6 and 2,5-TDI, exhibited monotropic liquid crystallinity, although these polyurethanes contained no mesogenic core unit. For example, LCPU-L(low molecular weight) exhibited T_(I.LC) of 122 ℃ and T_(LC-k) of 89℃.
Temperature Dependence of the Reaction HCl?+?OH?→?Cl?+?H2O between 140 and 1100?K
이종백,김도환 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.2
Temperature dependence of the molecule-radical reaction HCl?+?OH ? Cl?+?H2O at temperatures between 140 and 1100?K is studied using a quasiclassical trajectory method. Potential energy surfaces are formulated using pair-wise additive two-body, nonadditive three-body, and four-body analytic forms and long-range interactions. At temperatures above 300?K, the reaction occurs by direct collisions and the calculated rate constant fits the Arrhenius equation kdir = 4.85?? 10?12 exp.(?631?± 10/T) cm3/molecule/s. At temperatures below 300?K, the reaction is driven by an attractive potential and occurs through the formation of a ClH?OH collision complex, which is sufficiently long-lived to enhance quantum mechanical tunneling of the H atoms. The sum of the direct and complex-mode reaction rates effectively describes the reaction occurring at temperatures in the 140?1100?K temperature range.
MBL과 컴퓨터 시뮬레이션을 이용한 산·염기 중화 적정에서 적정곡선에 대한 연구
이종백,강대풍,김윤하,김영환,정민재,이상권 한국과학영재교육학회 2019 과학영재교육 Vol.11 No.3
This study is based on Research and Education (R&E) project in Chonnam National University. We explored the variation of the titration curve in the acid-base titration for various acids by both the experiment using the pH meter and MBL tool and the computer simulation. The pH variations in the titration experiment were recorded using pH meter and MBL apparatus by adding the titrant in the titration rate of 0.015mL/sec. The computer simulations were carried out using FORTRAN programming and compared with the experimental data. In the monoprotic strong acid-strong base reaction, the rapid pH variation on the equivalent point in the titration curve is occurred, thus the end point can be found easily in the acid-base neutralization titration experiment. In the monoprotic weak acid-strong base reaction, the rapid pH variation on the equivalent point in the titration curve is also occurred, thus the end point can be found easily. On the contrary, in the diprotic acid-strong base reaction, the pH variation on the equivalent point is dependent on the two acid dissociation constants significantly. For the weak diprotic acid, the evident rapid pH variation on the first equivalent point is generally occurred, whereas the evident rapid pH variation on the second equivalent point is not occurred. Furthermore, for the strong diprotic acid (H2SO4), the rapid pH variation on the equivalent point in the titration curve is occurred only on the second equivalent point. For considered all cases in this study, the computer simulations are significantly consistent with the experimental results, thus can elucidate the pH variations in the equivalent points. Therefore, we suggest that the end point can be found easily and exactly for any acid-base reaction if the computer simulation is carried out before the acid-base neutralization titration experiment. 이 연구는 전남대학교 과학영재교육원 사사과정에 서 진행하는 연구로 수행되었다. 본 연구에서는 산과 염기의 변화에 따른 산・염기 적정곡선의 변화를 pH 센서와 MBL을 이용한 적정 실험과 컴퓨터 시뮬레이션을 통해 살펴보았다. 적정 실험은 실린지 펌프와 MBL을 이용하여 0.015mL/초 간격으로 적정시약을 첨가하면서 적정용액의 pH 변화를 기록하였다. 다음으로 포트란 프로그래밍으로 산・염기 적정시 pH 변화를 시뮬레이션하여 실험결과와 비교하였다. 강산과 강염기의 적정곡선에서는 당량점에서 pH의 매우 급격한 변화가 있기 때문에 적정 실험을 통하여 pH 변화를 기록함으로써 종말점을 쉽게 찾아낼 수 있었다. 약산과 강염기의 적정곡선에서도 당량점에서는 pH 변화가 급격하기 때문에 적정 실험시 pH 변화를 기록함으로써 종말점을 쉽게 찾아낼 수 있었다. 한편, 이양성자산과 강염기의 적정에서는 이양성자산의 단계적 해리상수에 따라 당량점에서의 변화가 많은 영향을 받았다. 이양성자산 약산의 경우 첫 번째 당량점에서의 pH 변화는 대부분의 경우 뚜렷하게 나타나지만 이차 당량점은 산의 해리 상수에 따라 뚜렷하게 나타나지 않는 경우가 많았다. 더구나 황산의 경우에는 이차 당량점에서만 뚜렷한 pH 변화가 있었다. 본 연구에서 수행한 컴퓨터 시뮬레이션은 모든 산・염기 반응에 대해 실험적으로 나타난 산・염기 적정곡선과 매우 잘 일치하였으며 각 당량점에서의 pH 변화를 정확하게 설명할 수 있었다. 따라서 적정 실험을 행하기 전 컴퓨터 프로그래밍을 통해 산・염기 적정곡선을 시뮬레이션한 후 실험을 수행함으로써 당량점을 정확하게 확인할 수 있으리라 기대된다.
이종백,장경순,문경환,김유항,Lee, Jong Baek,Jang, Gyeong Sun,Mun, Gyeong Hwan,Kim, Yu Hang Korean Chemical Society 2001 Bulletin of the Korean Chemical Society Vol.22 No.8
The reaction of gas-phase atomic bromine with highly covered chemisorbed hydrogen atoms on a silicon surface is studied by use of the classical trajectory approach. It is found that the major reaction is the formation of HBr(g), and it proceeds th rough two modes, that is, direct Eley-Rideal and hot-atom mechanism. The HBr formation reaction takes place on a picosecond time scale with most of the reaction exothermicity depositing in the product vibration and translation. The adsorption of Br(g) on the surface is the second most efficient reaction pathway. The total reaction cross sections are $2.53{\AA}2$ for the HBr formation and $2.32{\AA}2$ for the adsorption of Br(g) at gas temperature 1500 K and surface temperature 300 K.