• 한국세라믹학회지
• /
• 제26권5호
• /
• pp.601-608
• /
• 1989

Electrical properties of ZrF4-based heavy metla fluoride glasses were measured by the ac complex impedance method. The effects of alkali and chloride ions addition into fluoro zirconate glasses on the electrical conductivity were examined. The electrical conductivities of fluoride glasses show Arrhenian behavior in the temperature range of the experiment and were decreased by the addition of sodium fluoride up to 15mol%. Mixed alkali substitution resulted in conductivity minimum at intermediate composition which is commonly observed as mixed alkali effect' in alkali oxide glasses. Chloride ion substituted for fluoride ion was found to lower the conductivity.

• 펄프종이기술
• /
• 제31권3호
• /
• pp.10-18
• /
• 1999

The influence of simple electrolyte or anionic trashes on cationic starch adsorption was examined using deinked pulp and bleached thermomechniical pulp. Adsorbed amounts of cationic starches increased slightly , then decreased abruptly as the concentration of simple electrolyte increased. This phenomenon was discussed based on the compression of electrical double layer and conformation change of starch molecules. Also, the effect of the type of simple electrolytes on starch adsorption was examined and discussed. Addition of sodium slilicate increased starch adsorption since it increased surface charge density of fibers. On the other hand, addition of kraft lignin decreased cationic demand of the pulp slurries and adsorbed amounts of cationic starches. Nonionic surfactant did not show any significant effect on the cationic demand of pulp slurries. When simple electrolytes were added to the stock , grater adsorption or cationic starches was obtained with starches of lower degree of substitution . On t도 other hand, amount of adsorbed starches decreased for lower DS starches when the concentration of anionic trashes increased.

• Macromolecular Research
• /
• 제13권3호
• /
• pp.229-235
• /
• 2005

Various alkoxyamine initiators for nitroxide mediated radical polymerization (NMRP) were prepared in high yields by a simple substitution reaction of nitroxide anions with benzyl bromide. The required nitroxide anions were easily generated by treating either nitroxide free radicals or hydroxy amine with an alkali metal such as sodium or potassium in THF. This method is both practical and efficient, since the ionic conditions prevent other side reactions from occurring, such as the self-coupling or oligomerization reactions that are observed in the case of radical trapping conditions. To demonstrate the utility of the resulting alkoxyamine initiators, end- and telechelic-alkoxyamine PEG macroinitiators derived from the alkoxyamines were synthesized by a simple chemical modification, and used for the preparation of PEG-b-PS and PS-b-PEG-b-PS block copolymers by NMRP.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
• /
• pp.130-131
• /
• 2016

In this study, moisture absorption coefficient and efflorescence properties of Ordinary Portland cement and alkali-activated slag cement mortar were assessed according to their red mud substitution ratio. Tests were conducted to determine the cause of efflorescence, which is a significant obstacle to the recycling of red mud as a sodium activator in alkali-activated slag cement, and to find a method to control efflorescence.

• 약학회지
• /
• 제58권6호
• /
• pp.371-377
• /
• 2014

A new series of 3-alkylthio-6-allylthio-4(or 5)-methylpyridazines (6a-e)-(7a-e) was synthesized from citraconic anhydride (1) for development of candidates possessing anticancer activity. The process involves the formation of pyridazine ring, dichlorination, monoallythiolation, and further another alkylthiolation. Compounds 6a-e, and 7a-e were prepared from 6-allylthio-3-chloro-4-methylpyridazine (4) or 6-allylthio-3-chloro-5-methylpyridazine (5) via nucleophilic substitution reaction with alkylthiol anion as nucleophile. Intermediates 4, and 5 could be converted to target pyridazines 6a-e, and 7a-e using 1~1.5 equivalent of alkylthiol at reflux temperature in methanol in the presence of sodium hydroxide. The structures of the synthetic compounds were characterized using NMR, IR, and GC-MS analyses.

• Bulletin of the Korean Chemical Society
• /
• 제9권6호
• /
• pp.384-388
• /
• 1988

New methods of the reduction of carboxylic acid salts to aldehydes with 2 equiv of thexylbromoborane-dimethyl sulfide (ThxBHBr${\cdot}SMe_2$) or 9-borabicyclo[3.3.1]nonane (9-BBN) are described. Both these reagents provide the corresponding aldehydes from various as sodium and lithium salts of carboxylic acids in high yields both at room temperature. Such facile reductions are explained as the simple substitution for the bromo group of ThxBHBr by a carboxylate to form thexyl(acyloxty)borane followed by reduction with excess reagent and the formation of an ate complex followed by reduction with excess 9-BBN.

• Bulletin of the Korean Chemical Society
• /
• 제20권10호
• /
• pp.1153-1158
• /
• 1999

β-Cyclodextrin, amylose, and cellulose were partially methylated and acetylated in order to examine the relative reactivities of 2-, 3-, and 6-OH groups to alkylation and acylation. The partially methylated samples of the polysaccharides were treated with excess of ethyl iodide and sodium hydroxide in dimethyl sulfoxide to convert all of the free hydroxyl groups to ethyl ether groups. The partially O-ethylated and O-methylated polysaccharides were reductively cleaved with triethylsilane in the presence of trimethylsilyl methanesulfonate and borontrifluoride etherate (5 : 1 by mole) and the resulting 4-OH group was acetylated and benzoylated to form mixtures of eight 4-O-acyl-1,5-anhydroalditols. The relative ratio of the alditol esters were analyzed by gas chromatography to determine the degree of substitution at each position. A similar sequence of reactions was carried out with partially acetylated polysaccharides. The results indicated that the order of relative reactivities for methylation are 2-OH > 6-OH > 3-OH and for acylation are 6-OH > 2-OH > 3-OH regardless of the anomeric configuration.

• Journal of the Korean Wood Science and Technology
• /
• 제41권4호
• /
• pp.302-309
• /
• 2013

Sodium hydroxide-urea 수용액을 이용한 다공성 셀룰로오스계 에어로겔은 용해, 겔화, 재생, 유기용매 치환과 동결건조과정에 의해 제조되었다. 에어로겔의 구조적 특성과 다공성은 주사전자현미경과 질소흡착장치를 이용하여 분석하였다. 그 결과, 용해펄프는 완전히 용해되었지만, 여과지와 홀로셀룰로오스는 원심분리과정에서 수용액에 용해된 부분과 용해되지 않은 부분으로 구분되었다. 용해펄프 에어로겔의 표면은 다공성 공극, 내부는 그물모양의 망목상 구조가 관찰되었다. 여과지와 홀로셀룰로오스 에어로겔은 표면이 압축된 다공성 네트워크 형태였고, 내부는 open-pore 구조의 나노피브릴 네트워크로 구성되었다. 홀로셀룰로오스 에어로겔에서 수용액에 용해되지 않는 형태의 섬유들이 관찰되었다. 용해펄프로부터 만들어진 에어로겔의 비표면적은 260~326 $m^2/g$ 범위였고, 농도 증가와 함께 감소하였다. 그러나 여과지 에어로겔의 비표면적(198~418 $m^2/g$)은 농도 증가와 함께 증가하였다. 홀로셀룰로오스 에어로겔은 2% 농도에서는 137 $m^2/g$로 농도의 증가와 함께 증가하여 4% 농도에서 401 $m^2/g$로 최댓값을 보여주었고, 5% 농도에서 감소하였다.

• 대한화학회지
• /
• 제37권2호
• /
• pp.249-254
• /
• 1993

N-p-nitrophenyl poly(m-phenylene isophthalamide)는 poly(m-phenylene isophthalamide)를 디메틸술폭사이드(DMSO) 용매속에서 수소화나트륨(NaH)과 반응시킨 후, 1-fluoro-4-nitrobenzene을 첨가하여 43 wt%를 얻었다. 고유점성도는 폴리머를 98% 황산에 녹여 $30^{\circ}C$에서 측정하였으며 그 값은 0.606g/cm${\cdot}$sec(0.125g/25ml)였다. Poly(m-phenylene isophthalamide) 합성에 있어서, 1,3-페닐디아민은 트리에틸아민과 트리에틸아민·염화수소가 있는 클로로포름 용매속에서 클로로이소프탈산과 반응에 의해 얻어졌다. 고유 점성도 값은 같은 조건에서 0.560g/cm${\cdot}$sec 였다. N-p-nitrophenyl poly(m-phenylene isophthalamide)의 치환비율은 $^1H-NMR$ integration에 의해 16.7~47.0%였다. 고유점성도가 큰 poly(m-phenylene isophthalamide)를 사용했을 때는 치환비율이 낮았다.

• 생명과학회지
• /
• 제25권8호
• /
• pp.896-902
• /
• 2015

본 연구는 유화형 돈육소시지 제조에 첨가되는 아질산염을 대체할 목적으로 천연색소로 알려진 레드비트 분말을 첨가하여 돈육소시지의 이화학적 특성에 미치는 영향에 대해 알아보고자 실시하였다. 총 5개의 처리구로 제조를 하였으며, C (아질산염 0.01%), T1 (아질산염 0.005% + 레드비트 분말 0.5%), T2 (아질산염 0.005% + 레드비트 분말 0.25%), T3 (레드비트 분말 0.5%), T4 (레드비트 분말 0.25%)로 처리하여 10±1℃에서 6주간 저장하면서 실험을 실시하였다. 명도는 Control이 유의적으로 높았고, 적색도는 T1이 높았으며, 황색도는 T3와 T4가 높았다. pH는 T3와 T4가 유의적으로 낮은 경향을 보였다. VBN은 처리구간별 유의적 차이가 없었다. DPPH 결과는 0주차에서 T1과 T3가 유의적으로 높은 경향을 보였으며, 2주차에서 T1이 높았고, 4주와 6주차에서는 T3가 높았다. 또한, 잔존아질산이온 결과는 Control이 저장 6주 동안 유의적으로 높았고, T3와 T4는 낮은 결과를 나타내었다. 따라서, 본 실험 결과에 의하면 레드비트 분말의 첨가는 유화형 돈육소시지의 품질을 감소시키지 않으면서 아질산염의 첨가를 줄일 수 있을 것으로 판단되었으며 항산화활성에 효과를 나타내는 것으로 사료되었다.