• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2004년도 춘계종합학술대회
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• pp.687-690
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• 2004

The preparation of A1203-SiO2 thin films from less than one micron to several tens of microns in thickness had been Prepared from metal alkoxide sols. Two methods, dip-withdrawal and electrophoretic deposition, were employed for thin films and sheets formation. The requirements to be satisfied by the solution for preparing uniform and strong films and by the factors affecting thickness and other properties of the films were examined. For the preparation of thin, continuous A12O3-SiO2 films, therefore, metal-organic-derived precursor solutions contained Si and Al in a chemically polymerized form has been developed and produced in a clear liquid state.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2003년도 제120회 추계학술대회 제 5차 한ㆍ일 치과보존학회 공동학술대회
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• pp.561-562
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• 2003

pH varies in the oral environment and on tooth surfaces. The surface of a plaque covered resinous restoration has a low pH. In human dental plaque a number of acids are produced by bacterial metabolism. The predominant acids are acetic, propionic and lactic acids. These acids induced a surface swelling of restorative resin. The swelling cause formation of pores inside the resin matrix from which organic substances can be released, resulting in a mass loss. The purpose of this study was to qualitatively and quantitatively analyse the leached monomers of dental composites after storage in acetate buffer solution as a function of time by means of high performance liquid chromatography(HPLC) / mass spectrometer and further determine whether pH and time has any influence on the degradation behavior of composite restoration.(omitted)

• Bulletin of the Korean Chemical Society
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• 제17권8호
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• pp.707-712
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• 1996

Growth and changes of electronically conducting polypyrrole (PPy) in the form of thin films polymerized on metal electrodes were investigated by electrochemical and in situ three-parameter ellipsometry methods at the wavelength of 632.8 nm. Although the optical equations produced multiple sets of solution, it was possible to determine a unique set of thickness and the optical constants of a film by auxiliary measurements and/or physical reasoning. The changes in the thickness and the optical properties of the polymers during polymerization and electrochemical oxidation/reduction was successfully followed by the three-parameter ellipsometric technique. The optical properties of the polymers continuously changed as the film grew. The imaginary part of the refractive index of polypyrrole seemed to be dominantly determined by the existence of an absorption band around the visible range.

• Bulletin of the Korean Chemical Society
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• 제7권5호
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• pp.372-376
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• 1986

Substituted 3,4-dihydro-2H-pyrans ($1_{a-e}$) were prepared by (4 + 2) cycloaddition reaction of dimethyl dicyanofumarate with the corresponding electron-rich olefins. The compounds $1_{a-e}$ were ring-open polymerized by cationic initiators to obtain polymers of 1:1 alternating sequence. Polymerizations were carried out with boron trifluoride etherate in methylene chloride at $-78^{\circ}C$. All the polymers obtained were soluble in common solvents and were reprecipitated by pouring its chloroform solution into diethyl ether. All the compounds $1_{a-e}$ were not as reactive as the corresponding pyrans derived from ${\alpha}$ -cyanoacrylate.

• Bulletin of the Korean Chemical Society
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• 제19권6호
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• pp.680-685
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• 1998

Two kinds of new aliphatic diols were synthesized by the ring-opening reaction of lactide and glycolide with 1,4-butanediol, a difunctional initiator, in the presence of stannous octoate. The resulting aliphatic diols were melt-polymerized with D-tartaric acid at 150 ℃ to produce new crosslinkable polyesters. They were reacted with hexamethylene diisocyanate in THF at 65 ℃ in a teflon mold for 24 h to prepare sequentially ordered crosslinked polyesters (BD/LT/GL/D-tartarate). Degradation of the prepared yellow crosslinked films was carried out in a buffer solution in order to examine the effect of time, pH, temperature and crosslinking degree on their degradation rate and mechanism. The rate of degradation increased with an increase in pH and temperature, but it decreased with increasing degree of crosslinkage incorporated into the crosslinked polyesters. We also found that the crosslinked polymers were converted into the acidic compounds such as lactic, glycolic, and D-tartaric acids during the degradation.

• Bulletin of the Korean Chemical Society
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• 제14권2호
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• pp.283-287
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• 1993

p-(2,2,3,3-Tetracyanocyclopropyl)phenyl acrylate (3a) and p-(2,2,3,3-tetracyanocyclopropyl)phenyl methacrylate (3b) were prepared by the reactions of bromomalononitrile with p-acryloyloxybenzylidenemalononitrile (2a) or p-methacryloyloxy-benzylidenemalononitrile (2b), respectively. Compounds 3a and 3b were polymerized with free radical initiators to obtain the polymers with multicyano functionalities in the cyclopropane ring. The resulting polymer 4a was soluble in acetone but the polymer 4b was not soluble in common solvents. The inherent viscosities of polymers 4a were in the range of 0.10-0.15 dL/g in acetone and those of 4b were in the range of 0.20-0.30 dL/g in 98% sulfuric acid. Solution-cast films were cloudy and brittle, showing $T_g$ values in the range of 106-125$^{\circ}$C.

• Bulletin of the Korean Chemical Society
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• 제19권2호
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• pp.155-159
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• 1998

o-(2-Vinyloxyethoxy)benzylidenemalononitrile (4a), methyl o-(2-vinyloxyethoxy)benzylidenecyanoacetate (4b), m-(2-vinyloxyethoxy)benzylidenemalononitrile (5a), methyl m-(2-vinyloxyethoxy)benzylidenecyanoacetate (5b), p-(2-vinyloxyethoxy)benzylidenemalononitrile (6a), and methyl p-(2-vinyloxyethoxy)benzylidenecyanoacetate (6b) were prepared by the condensation of o-(2-vinyloxyethoxy)benzaldehyde (1), m-(2-vinyloxyethoxy)benzaldehyde (2), and p-(2-vinyloxyethoxy)benzaldehyde (3) with malononitrile or methyl cyanoacetate, respectively. Bifunctional vinyl ether monomers 4a-b and 6a-b polymerized readily with cationic initiators to give polymers with the NLO-chromophores o- and p-oxybenzylidenemalononitrile or o- and p-oxybenzylidenecyanoacetate in side chain at -60 ℃, while meta-isomers 5a and 5b gave lower yields of polymers under the same conditions. The resulting polymers 7-9 were soluble in common organic solvents and the inherent viscosities of polymers were in the range of 0.20-0.30 dL/g in acetone. Solution-cast films were clear and brittle, showing Tg values in the range of 40-70 ℃.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2616-2622
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• 2013

A novel zwitterionic monomer 3-[(2-acrylamido)dimethylammonio]propanesulfonate (DMADAS) was designed and synthesized in this study. Then it was polymerized with acrylamide (AM) by free radical polymerization in 0.5 mol/L NaCl solution with ammonium persulfate ($(NH_4)_2S_2O_8$) and sodium sulfate ($NaHSO_3$) as initiator. The structure and composition of DMADAS and acrylamide-3-[(2-acrylamido)-dimethylammonio]propanesulfonate copolymer (P-AM-DMADAS) were characterized by FT-IR spectroscopy, $^1H$ NMR and elemental analyses. Isoelectric point (IEP) of P-AM-DMADAS was tested by nanoparticle size and potential analyzer. Solution properties of copolymer were studied by reduced viscosity. Antipolyelectrolyte behavior was observed and was found to be enhanced with increasing DMADAS content in copolymer. The results showed that the viscosity of P-AM-DMADAS is 5.472 dl/g in pure water. Electrolyte was added, which weakened the mutual attraction between sulfonic acid group and quaternary ammonium group. The conformation became loose, which led to the increase of reduced viscosity. The ability of monovalent and divalent cation influencing the viscosity of zwitterionic copolymer obeyed the following sequence: $Li^+$ < $Na^+$ < $K^+$, $Mg^{2+}$ < $Ca^{2+}$ < $Ba^{2+}$, and that of anion is in the order: $Cl^-$ < $Br^-$ < $I^-$, $CO{_3}^{2-}$ > $SO{_3}^{2-}{\approx}SO{_4}^{2-}$.

• Restorative Dentistry and Endodontics
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• 제29권3호
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• pp.249-266
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• 2004

The purpose of this study was to determine whether pH and time has any influence on the degradation behavior of composite restoration by analyzing the leached monomers of dental composites qualitatively and quantitatively after storage in acetate buffer solution as a function of time using high performance liquid chromatography (HPLC) / mass spectrometer. Materials and Methods：Three commercial composite restorative resin materials (Z-250, Heliomolar and Aeliteflo) with different matrix structure and filler composition were studied. Thirty specimens (7mm $diameter{\times}2mm$ thick) of each material were prepared. The cured materials were stored in acetate buffer solution at different pH (4, 7) for 1, 7 and 45days. As a reference, samples of unpolymerized composite materials of each product were treated with methanol (10mg/ml). Identification of the various compounds was achieved by comparison of their mass spectra with those of reference compound, with literature data. and by their fragmentation patterns. Data were analysed statistically using ANOVA and Duncan's test. Results：1. Amounts of leached TEGDMA in Aeliteflo were significantly larger than those of UDMA in Z-250 and Heliomolar at experimental conditions of different storage time and pH variation (p<0.001). 2. As to comparison of the amounts of leached monomers per sorage time, amounts of leached TEGDMA in Aeliteflo and UDMA in Z-250 and Heliomolar were increased in the pH 4 solution more significantly than in the pH 7 solution after 1day, 7days and 45days, respectively (p<0.001). 3. In total amounts of all the leached monomers with storage times, the overall amounts of pH 4 extracts were larger than those of pH 7 extracts for all resin groups, but there was no significant difference (p>0.05).

• 공업화학
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• 제9권1호
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• pp.44-51
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• 1998

본 실험에서 QCA를 사용하여 $NaClO_4$, $LiClO_4$, $KClO_4$전해질 용액에서 전기중합한 폴리피롤 박막의 점탄성 특성을 in situ 분석하였다. 수정진동자를 특수 제작한 전기화학 분석셀에 넣어 수정진동자의 한쪽 전극을 작용전극으로 사용하였다. 공진주파수와 공진저항 상관도 (F-R)도를 이용하여 폴리피롤 박막의 점탄성을 해석하였고 AFM 사진과 비교 검토하였다. 피롤을 정전류에서 중합하여 피막한 수정진동자를 이용하여 순환전위주사하면서 공진주파수, 공진저항, 전류를 측정하여 폴리피롤 박막의 산화-환원 반응 거동을 분석하였다. 본 실험 결과, 전기중합 초기에는 피롤 박막이 탄성적으로 거동하다가 중합되어 감에 따라 점차 점탄성막으로 변하여 감을 알 수 있었다. 동시에 박막 사이로 전해질 용액이 침투됨에 따라 박막의 두께가 증가하면서 표면 형상도 변화하였다. 이와 같은 현상은 중합할 때의 전해질과 전위주사할 때의 전해질 용액을 변화시키면서 순환전위주사하여도 발생하였다.