• 멤브레인
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• 제22권3호
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• pp.191-200
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• 2012

불소관능기인 perfluorocyclobutane (PFCB)기를 포함하는 후술폰화 poly (arylene ether sulfone) 랜덤 공중합체를 다공성 Polytetrafluoroethylene (PTFE) 막에 함침시켜 새로운 복합막을 제조하였다. 후술폰화 랜덤 공중합체는 trifluorovinyloxy 그룹을 양말단에 포함하는 biphenyl계와 sulfonyl계 단량체로부터 제조되었는데, biphenyl계와 sulfonyl계의 비율을 6 : 4와 4 : 6으로 조절 후 중부가반응 형태의 열중합과 chlorosulfonic acid (CSA)를 이용한 후술폰화 반응을 통하여 얻어졌다. 이렇게 제조된 랜덤 공중합체의 농도를 달리하면서(5~20 wt%) 다공성 PTFE 막에 함침시켜 복합막을 제조하였고, 이온 교환 능력(IEC), 함수율, 이온전도도를 측정하여 강화되지 않은 랜덤공중합체 및 Nafion과 비교하였다. 제조된 단량체 및 고분자의 구조와 순도는 각각 $^1H$-NMR, $^{19}F$-NMR와 FT-IR를 통하여 확인하였으며, 제조된 복합막의 형태는 SEM으로 관찰하였다.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4161-4164
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• 2012

Density functional MO calculations for the methylsilole anion of $[C_4H_4SiMe]^-$ and methylgermole anion of $[C_4H_4SiMe]^-$ at the B3LYP (full)/6-311+$G^*$ level (GAUSSIAN 94) were carried out and characterized by frequency analysis. The ground state structure for the methylsilole anion and methylgermole anion is that the methyl group is pyramidalized with highly localized structure. The difference between the calculated $C_{\alpha}-C_{\beta}$ and $C_{\beta}-C_{\beta}$ distances are 9.4 and 11.5 pm, respectively. The E-Me vector forms an angle of $67.9^{\circ}$ and $78.2^{\circ}$ with the $C_4E$ plane, respectively. The optimized structures of the saddle point state for the methylsilole anion and methylgermole anion have been also found as a planar with highly delocalized structure. The optimized $C_{\alpha}-C_{\beta}$ and $C_{\beta}-C_{\beta}$ distances are nearly equal for both cases. The methyl group is located in the plane of $C_4E$ ring and the angle between the E-Me vector and the $C_4E$ plane for the methylsilole anion and methylgermole anion is $2.0^{\circ}$ and $2.3^{\circ}$, respectively. The energy difference between the ground state structure and the transition state structure is only 5.1 kcal $mol^{-1}$ for the methylsilole anion. However, the energy difference of the methylgermole anion is 14.9 kcal $mol^{-1}$, which is much higher than that for the corresponding methylsilole monoanion by 9.8 kcal $mol^{-1}$. Based on MO calculations, we suggest that the head-to-tail dimer compound, 4, result from [2+2] cycloaddition of silicon-carbon double bond character in the highly delocalized transition state of 1. However, the inversion barrier for the methylgermole anion is too high to dimerize.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2193-2199
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• 2012

A series of novel polytriazoleimides were prepared from various aromatic dianhydrides and a new kind of 1,2,3-triazole-containing aromatic diamine synthesized by the Cu (I)-catalyzed 1,3-dipolar cycloaddition reaction in DMAc, and characterized by FT-IR, $^1H$-NMR, XRD, DSC and TGA techniques. The results show the polytriazoleimides are soluble in most of strong polar solvents and have inherent viscosity values of 0.51-0.62 dL/g(DMAc). The polytriazoleimide films exhibit a tensile strength of 62.3-104.5 MPa and an elongation at breakage of 4.0-8.1%, a glass transition temperature ($T_g$) of $257-275^{\circ}C$, a decomposition temperature (at 5% weight loss) of $350-401^{\circ}C$ in $N_2$ atmosphere, and a dielectric constant of 2.47-3.01 at 10 MHz, which depend on the structure of the polymers. The polytriazoleimides perform good resistance to acid and alkali solution.

• 대한화학회지
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• 제28권5호
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• pp.284-292
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• 1984

치환체-E-arene-diazocyanides와 nitrosobenzenes의 (4+2) 고리첨가 반응의 배향성에 대한 치환기 및 산 촉매효과와 반응성을 예측하기 위하여 Diels-Alder 반응의 열 또는 촉매반응에 대하여 Frontier orbital theory (FMO)이론을 적용해서 CNDO/2 방법과 EHT-SPD 방법으로 고찰하였다. (1) 위 반응은 Hammett 식의 rho(${\rho}$)값이 양이므로 normal electron demand 반응형태를 가지며 4-FMO 및 Anh 방법이 실험적인 주 배향체와 일치함을 알았다. (2)전자끄는 기로 치환되면 dienophile의 HOMO, LUMO 궤도함수에너지가 낮아지고 반응성이 커지는 것을 알았다. (3)Lewis 산은 dienophile과 착물을 형성하고 dienophile의 LUMO계수를 정 반대로 분극시켜 주므로 주 배향제는 B형으로 예측된다. (4) diene HOMO-dienophile LUMO 상호작용의 안정화 에너지 (${\Delta}$E)와 Hammett식의 시그마 (${\sigma}$)값과의 그라프에서는 좋은 직선성을 보여 주었다.

• Bulletin of the Korean Chemical Society
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• 제8권2호
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• pp.96-101
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• 1987

2-Ethoxy-6-methoxy-5-cyano-3,4-dihydro-2H-pyran (1_a$), 2-n-butoxy-6-methoxy-5-cyano-3,4-dihydro-2H-pyr an (1b), 2-isobutoxy-6-methoxy-5-cyano-3,4-dihydro-2H-py ran ($1_c$), and 2-ethoxy-6-methoxy-3-methyl-5-cyano-3,4-dihydro -2H-pyran ($1_d$) were prepared by (4 + 2) cycloaddition reaction of methyl $\alpha$-cyanoacrylate with the corresponding alkyl vinyl ethers. Compounds $1_{a-d}$ were ring-open polymerized by cationic catalyst to obtain alternating head-to-head (H-H) copolymers. For comparison, head-to-tail (H-T) copolymer $3_a$ was also prepared by free radical copolymerization of the corresponding monomers. The H-H copolymer exhibited minor differences in its $1_H% NMR and IR spectra, but in the $^{13}C$ NMR spectra significant differences were observed between the H-H and H-T copolymers. Glass transition temperature ($T_g$) of H-H copolymer was higher than that of the H-T copolymer, but thermal decomposition temperature of the H-H copolymer was lower than that of the H-T copolymer. Compounds $1_a$, $a_b$, and $1_c$, copolymerized well with styrene by cationic catalyst, but compound 1d failed to copolymerize with styrene. All of the H-H and H-T copolymers were soluble in common solvents and the inherent viscosities were in the range 0.2-0.4 dl/g.

• Journal of Ginseng Research
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• 제48권4호
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• pp.366-372
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• 2024

Background: The biological activity and pharmacological effects of rare ginsenosides have been proven to be superior to those of the major ginsenosides, but they are rarely found in ginseng. Methods: Ginsenoside Rb1 was chemically transformed with the involvement of methanol molecules by a synthesized heterogeneous catalyst 12-HPW@MeSi, which was obtained by the immobilization of 12-phosphotungstic acid on a mesoporous silica framework. High-performance liquid chromatography coupled with mass spectrometry was used to identify the transformation products. Results: A total of 18 transformation products were obtained and identified. Methanol was found to be involved in the formation of 8 products formed by the addition of methanol molecules to the C-24 (25), C-20 (21) or C-20 (22) double bonds of the aglycone. The transformation pathways of ginsenoside Rb1 involved deglycosylation, addition, elimination, cycloaddition, and epimerization reactions. These pathways could be elucidated in terms of the stability of the generated carbenium ion. In addition, 12-HPW@MeSi was able to maintain a 60.5% conversion rate of Rb1 after 5 cycles. Conclusion: Tandem and high-resolution mass spectrometry analysis allowed rapid and accurate identification of the transformation products through the characteristic fragment ions and neutral loss. Rare ginsenosides with methoxyl groups grafted at the C-25 and C-20 positions were obtained for the first time by chemical transformation using the composite catalyst 12-HPW@MeSi, which also enabled cyclic heterogeneous transformation and facile centrifugal separation of ginsenosides. This work provides an efficient and recyclable strategy for the preparation of rare ginsenosides with the involvement of organic molecules.

• 폴리머
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• 제34권6호
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• pp.565-573
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• 2010

IPN 구조를 가지는 감습성 고분자 전해질로 사용하기 위하여 디브로모알칸과 가교가 가능한 copoly(2-(dimethylamino) ethyl methacrylate)(DAEMA)/butyl acrylate(BA)와 광가교가 가능한 copoly(methyl methacrylate) (MMA)/BA/2-(cinnamoyloxy)ethyl methacryate(CEMA)를 제조하였다. 전극의 기재 표면에 광조사에 의한 IPN-감습성 전해질의 부착을 위하여 3-(triethoxysilyl)propyl cinnamate(TESPC)을 전극표면에 처리하였다. IPN 구조의 감습성 고분자 필름은 copoly(DAEMA/BA), copoly(MMA/BA/CEMA) 및 1,4-dibromobutane(DBB) 가교제의 혼합 용액에 침적한 후에 UV 조사와 동시에 가열하여 제조하였다. IPN-전해질 고분자의 전극 기재와의 부착은 광화학적 $[2{\pi}+2{\pi}]$ 환화반응에 의하여 진행하였다. 얻어진 습도센서는 20~95%RH의 영역에서 매우 높은 감도와 1.5%RH 이하의 작은 히스테리시스를 보여주었다. 또한, 33~94%RH 사이에서 가습과 제습과정의 응답 및 회복 속도는 각각 48초와 65초로 나타나 매우 빠름을 알 수 있었다. 그 밖에 감습액 중의 공중합체의 농도, 가교제의 양, 가교반응 시간 등이 내수성을 포함한 감습성질에 미치는 영향을 조사하였다.

• 폴리머
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• 제34권4호
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• pp.313-320
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• 2010

신나메이트기를 갖는 새로운 자기 경화형 감습성 고분자 및 고분자형 앵커제로 사용하기 위하여 [2-[(methacryloyloxy) ethyl]dimethyl]propyl ammonium bromide(MEPAB), methyl methacrylate(MMA), 3-(trimethoxysilyl) propyl methacrylate(TMSPM) 및 2-(cinnamoyloxy)ethyl methacrylate(CEMA)의 공중합체들 을 합성하였다. 광가교성 공중합체들로서 MEPAB/MMA/TMSPM/CEMA＝70/20/0/10의 조성을 갖는 공중합체는 감습성 전해질 고분자로서, 그리고 50/0/20/30과 0/0/50/50 조성은 고분자형 부착제로 사용하였다. 이들 광가교형 고분자 실란커플링 처리제의 전극 표면과 부착 특성을 비교하기 위하여 3-(triethoxysilyl)propyl cinnamate(TESPC)도 표면 부착을 위한 표면처리제로서 사용하였다. 표면처리제는 전극의 기재 표면 위에 공유결합을 통하여 광가교성 신나 메이트 박막을 형성시킬 수 있었으며 센서에 UV가 조사되었을 때 전해질 고분자가 [2$\pi$+2$\pi$] 환화반응을 이용한 가교반응으로 기재에 부착되었다. 이렇게 고분자 표면처리제 및 TESPC로 처리된 센서들은 24시간 물에 침적시켰을 때 60~85%의 저항 증가가 생겼으며 이것은 상대습도 변화로서 2.25~3.15%RH에 해당하였다. 또한, -0.2%RH 이하의 양호한 히스테리시스, 90초의 응답 및 회복속도, 그리고 80 $^{\circ}C$ 및 90%RH의 고온 고습에서 매우 좋은 신뢰성을 보여주었다.