• Title, Summary, Keyword: chain transfer constants

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Effect of Substituent of Chain Transfer agent in the Free Radical Polymerization (자유 라디칼 중합반응에서 사슬이동제의 치환기 효과)

  • Chung, I.
    • Elastomers and Composites
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    • v.40 no.1
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    • pp.53-58
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    • 2005
  • Carbon tetrachloride is very reactive chain transfer agent due to the resonance stability of the trichlorocarbon radicals after breaking of C-Cl bond. Effect of benzylic radical comparing to trichlorocarbon radicals in the chain tranrfer reactions was investigated. From the structural point of view, cumyl chloride is a good candidate because it has the C-Cl bond with benzylic radicals after displacement of C-Ci bond. The reactivity of free radical polymerization of styrene in the presence of cumyl chloride was compared with that of carbon tetrachloride by calculating chain transfer constants. Results show that the cumyl chloride acts as a stronger chain transfer agent than carbon tetrachloride. The calculated chain transfer constant of cumyl chloride shows higher value (0.0463) than that of carbon tetrachloride (0.0011) in the styrene polymerization. High reactivity of cumyl chloride comparing to that of carbon tetrachloride is probably due to the higher resonance stability or benzylic radical than that or trichlorocarbon radicals after breaking of C-Cl bond. Monte Carlo simulation method is applied for characterizing the validity of kinetic constants according to the ratio of chain transfer agent to monomer.

Chain Transfer to Monomer and Polymer in the Radical Polymerization of Vinyl Neo-decanoate

  • Balic, Robert;Fellows, Christopher M.;Van Herk, Alex M.
    • Macromolecular Research
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    • v.12 no.4
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    • pp.325-335
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    • 2004
  • Molecular weight distributions of poly(vinyl neo-decanoate) produced by the bulk polymerization of the monomer to low conversions were investigated to obtain values of the rate constants for the chain transfer to monomer ( $C_{M}$). The value of $C_{M}$ of 7.5($\pm$0.6)${\times}$10$^{-4}$ was obtained from a logarithmic plot of the number distribution at 5,25, and 5$0^{\circ}C$, which suggests that the activation energy for chain transfer is on the order of 20-25 kJ ㏖$^{-1}$ . These plots were linear between the number and weight-average degrees of polymerization, but not over the whole molecular weight range for which a significant signal was observed in the gel permeation chromatography (GPC) trace. Modeling suggests that the deviations observed at high molecular weights can be explained by branching of the chains through chain transfer to the polymer, with a branching density as low as 10$^{-5}$ , without affecting the slope at low values of the number of monomer unit, N. This deviation from the expected distribution of linear chains was used to estimate the branching densities at low conversion.ion.

Comparison to Dielectric Properties of LB Films for Length of Methylene Group (메틸렌기의 길이에 따른 LB막의 유전 특성 비교)

  • Kang, Ki-Ho;Kim, Do-Kyun;Choi, Yong-Sung;Chang, Jeong-Soo;Kwon, Young-Soo
    • Proceedings of the KIEE Conference
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    • pp.1843-1845
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    • 1999
  • We have investigated the dielectric characteristics of palmitic acid(PA), stearic acid (SA) and arachidic acid(AA) Langmuir-Blodgett(LB) films because these fatty acid systems have a same hydrophilic group and a different hydrophobic one (alkyl chain length). In this work. fatty acid systems were used as LB films and the status of the deposited films was confirmed by evaluating the transfer ratio. the UV absorption and the capacitance. Also, the dielectric characteristics such as the frequency-capacitance characteristics and the dielectric dispersion and absorption characteristics of PA, SA and AA through-plane were measured. The relative dielectric constants of PA, SA and AA LB films were about $2.6\sim4.6$, $2.4\sim4.1$ and $2.2\sim3.8$, respectively. That is, the relative dielectric constants were decreased in proportion to the chain length of methylene group. And, the dielectric dispersion and absorption of each fatty acid LB films have arisen from spontaneous polarization of dipole polarization in the range of $10^4\sim10^5[Hz]$.

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New Tridentate Ligands with Mixed Donor Atoms for Cu-Based Atom Transfer Radical Polymerization

  • Cho, Hong-Youl;Han, Byung-Hui;Kim, Il;Paik, Hyun-Jong
    • Macromolecular Research
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    • v.14 no.5
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    • pp.539-544
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    • 2006
  • 2-Furancarboxaldehyde-2-pyridinylhydrazone (FPH) and 5-methyl-2-furancarboxaldehyde-2-pyridinylhydrazone (MFPH) were synthesized and used as tridentate ligands of copper (I) bromide for the atom transfer radical polymerization of methyl methacrylate (MMA) and styrene. The polymerization of methyl methacrylate achieved high conversion and yielded polymers with a good control of molecular weight and low polydispersity (PDI=1.33). Higher PDI were observed in the polymerization of styrene. Using 1-phenyl ethylbromide (PEBr) and ethyl 2-bromoisobutyrate (EBiB) as model compounds for the polymeric chain ends, the activation rate constants of the new catalytic systems were measured. These results were correlated with the polymerization results and compared with another catalytic system previously reported.

Dielectric and Electrical Characteristics of Fatty Acid System LB Filmes According to Length of Methylene Group (메틸렌기의 길이에 따른 지방산계 LB막의 유전 및 전기적 특성)

  • 김도균;강기호;최용성;권영수
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.4
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    • pp.300-305
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    • 2000
  • We have investigated the dielectric and electrical characteristics of palmitic acid(PA) stearic acid(SA) and arachidic acid(AA) Langmuir-Blodgett(LB) films because these fatty acid systems have a same hydrophilic group and a different hydrophobic one(methylene group or alkyl chain length). The fatty acid systems were used as LB films and the status of the deposited films was confirmed by evaluating the transfer ratio the UV absorption and the capacitance. The dielectric characteristics such as the frequency-capacitance characteristics and the dielectric dispersion and absorption characteristics of PA SA and AA through-plane were measured. The relative dielectric constants of PA, SA and AA LB films were about 3.0~4.6, 2.7~3.0 and 2.4~3.0 respectively. That is the relative dielectric constants were decreased in proportion to the chain length of methylene group. Also the dielectric dispersion and absorption of each fatty acid LB films have arisen from spontaneous polarization of dipole polarization in the range of 10$^4$~10$^{5}$ [Hz]. The conductivity of PA, SA and AA LB films obtained from I-V characteristics were about 9$\times$10$^{-14}$ , 3$\times$10$^{-14}$ and 5$\times$10$^{-15}$ [S/cm]. respectively. These results have shown the insulating materials and could control the conductivity y changing the length of methylene group. Also we have confirmed that the barrier height of fatty acid systems were almost the same ones obtained from dielectric characteristics.

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Synthesis of Poly(vinyl pivalate) Telomer Through Telomerization of Vinyl Pivalate (피발산 비닐의 텔로머화반응을 이용한 폴리(피발산 비닐) 텔로머 합성)

  • 김도균;조창기
    • Polymer(Korea)
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    • v.27 no.1
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    • pp.26-32
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    • 2003
  • Poly(vinyl pivalate)(PVPi) telomer containing bifunctional end groups was synthesized through radical telomerization of vinyl pivalate. The number-average molecular weight ($\bar{M}$n) of the synthesized telomers was investigated by GPC, $^1$H-NMR, and viscometric methods. PVPi telomers having a number-average molecular weight ($\bar{M}$n) of 2400~1300 g/mol were obtained. In order to control the molecular weight of telomers, chain transfer constants ($C_s$) of telogen ($CCl_4$) were determined by using the Mayo equation and simulation, which were 1.15, 1.16, and 1.18 at 40, 50, and 6$0^{\circ}C$, respectively. $\bar{M}$n of the synthesized telomers at 6$0^{\circ}C$ were between 5100 and 5400 g/mol at conversion of increasing from 18 to 72%. Those are corresponding to simulation results.

An Effect of Ethanol on Polypyrrole-Glucose Oxidase Enzyme Electrode (Polypyrrole-Glucose oxidase 효소전극의 Ethanol 첨가효과)

  • 김현철;구할본;사공건
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.147-150
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    • 1999
  • In the case of immobilizing of glucose oxidase in organic polymer using electrosynthesis, the glucose oxidase obstructs charge transfer and mass transport during the film growth. This may lead to short chained polymer and/or make charge-coupling weak between the glucose oxidase and the backbone of the polymer. That is mainly due to insulating property and net chain of the glucose oxidase. Since being the case, it is useless to increase in amount of glucose oxidase more than reasonable in the synthetic solution. We establish qualitatively that amount of immobilization can be improved by adding a little ethanol in the synthetic solution. As ethanol was added by 0.1 rnol dm" in the synthetic solution, Michaelis-Menten constants of the resulting enzyme electrode decreased from 30.7 mmol $dm^{-3}$ to about 2 mmol $dm^{-3}$. That suggests increase in affinity of the enzyme electrode for glucose and in amount of the immobilized enzyme.zyme.

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Copolymerization of Diethyl Isopropenyl Phosphate with Vinyl Acetate and Acrylonitrile (인산디에틸 이소프로페닐과 초산비닐 및 아크릴로니트릴의 혼성중합)

  • Jung-Il Jin;Hong-Ku Shim;Soo-Min Lee
    • Journal of the Korean Chemical Society
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    • v.26 no.6
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    • pp.421-426
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    • 1982
  • Free radical-initiated copolymerization of diethyl isopropenyl phosphate (DEIPA) with vinyl acetate (VAc) and acrylonitrile (AN) was studied. The monomer reactivity ratios for the monomer pairs, determined at $60^{\cric}C$ using benzoyl peroxide as an initiator, are: ${\gamma}_1$(VAc) = 1.56, ${\gamma}_2$(DEIPA) = 0.44: ${\gamma}_1$(AN) = 15.2, ${\gamma}_2$(DEIPA) = 0.031. The values of the Alfrey-Price constants, Q and e, for DEIPA were calculated to be 0.015 and 0.39, respectively, from the VAc system, and 0.014 and 0.34, respectively, from AN/DEIPA pair. These results indicate that ${\alpha}$-methyl substituent of vinyl phosphate monomer decreases the general reactivity in free radical copolymerization. The intrinsic viscosity and number-average molecular weight of copolymers decreased as their content of DEIPA units increased, indicating a high degree of chain transfer caused by DEIPA, as previously learned in DEVPA system.

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