• Title, Summary, Keyword: free radical polymerization

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Estimation of Activation Energy for the Free Radical Polymerization by Using Isoconversional Analysis (등전환 분석(Isoconversional Analysis)를 이용한 자유라디칼 중합의 활성화 에너지 계산)

  • Chung, I.
    • Elastomers and Composites
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    • v.39 no.4
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    • pp.281-285
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    • 2004
  • In this paper, the simple way to evaluate the value of the activation energy for the overall rate of free radical polymerization by using DSC thermograms was studied using free radical polymerization or butylacrylate as a model. Activation ehergies were determined at heating rates of 1, 2, 5, and $10^{\circ}C/min$ by applying the multiple scanning-rate methods of Kissinger, Osawa, and half-width methods as well as the single rate method of Barrett. The value of the overall activation energy measured was closely matched with the values calculated from individual data. This work also demonstrated that the use of the isoconversional method was a simple and effective way to estimate the activation energy for the overall free radical polymerization.

The Effect of Camphorsulfonic Acid in TEMPO-Mediated Bulk and Dispersion Polymerization of Styrene

  • Oh Sejin;Kim Gijung;Ko Narae;Shim Sang Eun;Choe Soonja
    • Macromolecular Research
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    • v.13 no.3
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    • pp.187-193
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    • 2005
  • The TEMPO-mediated living free-radical bulk and dispersion polymerization of styrene in the presence of camphorsulfonic acid (CSA) are investigated. In the absence of TEMPO and CSA in the bulk polymerization, a conversion of $93\%$ is achieved within 6 hr of polymerization. When only TEMPO is involved in this polymerization, the pseudo-living free-radical polymerization is well achieved, however, the polymerization rate becomes quite slow. This retardation of the polymerization rate is solved by the addition of a low concentration of CSA. In the TEMPO-mediated dispersion polymerization in the presence of CSA, similar trends in the conversion, kinetics, and PDI are observed as those observed in the case of bulk polymerization. When only TEMPO is used in the dispersion polymerization, the resulting particle size becomes quite broad, due to the prolonged polymerization time. However, when a 1.0 molar ratio of CSA to TEMPO is added to the TEMPO-mediated dispersion polymerization, fairly mono-disperse PS microspheres having an average size of 5.83 $\mu$m and a CV of 3.4$\%$ are successfully obtained, due to the narrow molecular weight distribution of the intermediate oligomers and shortening of the polymerization time. This result indicates that the addition of CSA to the TEMPO-mediated bulk and the use of dispersion polymerization not only shortens the polymerization time, but also greatly improves the uniformity of the microspheres.

Synthesis of Star-like Random Copolymers from Resorcinarene-Based Octa-Functional Alkoxyamine Initiator via Nitroxide Mediated Free Radical Polymerization

  • Abraham, Sinoj;Choi, Jae-Ho;Lee, Jin-Kyu;Ha, Chang-Sik;Kim, Il
    • Macromolecular Research
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    • v.15 no.4
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    • pp.324-329
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    • 2007
  • An octa-functional alkoxyamine initiator, with the 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO) free radical, was synthesized based on resorcinarene, with its efficiency to initiate the nitroxide-mediated free radical copolymerization of styrene and methyl methacrylate (MMA) described. A difunctional analogue of this initiator was also synthesized, using resorcinol as the core molecule. The structures of the resulting initiators were confirmed by homolysis studies based on electron spin resonance spectroscopy and molecular modeling. The polymerization behavior and characteristics of the polymers obtained using these two initiators were also compared. Well-defined star-shaped and linear random copolymers, with low polydispersities and controlled molecular weights, were prepared. The efficiencies of these initiators towards copolymerization, as well as the parameters permitting the formation of well-defined polymers, were also investigated. The reactivity ratios were $r_a=0.42(a=styrene)\;and\;r_b=0.33(b=MMA)$ for the octa-functional initiator system and $r_a=0.45\;and\;r_b=0.39$ for the difunctional initiator system.

Free Radical Polymerization Algorithm for a Thermoplastic Polymer Matrix : A Molecular Dynamics Study (무정형 열가소성 고분자의 자유 라디칼 중합 분자동역학 시뮬레이션 알고리즘)

  • Jung, Ji-Won;Park, Chan-Wook;Yun, Gun-Jin
    • Composites Research
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    • v.32 no.3
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    • pp.163-169
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    • 2019
  • In this paper, we constructed a molecular dynamics (MD) polymer model of PMMA with 95% of conversion by using dynamic polymerization algorithm of a thermoplastic polymer based on free radical polymerization. In this algorithm, we introduced a united-atom level coarse-grained force field that combines the non-bonded terms from the TraPPE-UA force field and the bonded terms from the PCFF force field to alleviate the computation efforts. The molecular weight distribution and the average molecular weight of the polymer were calculated by investigating each chain generated from the free radical polymerization simulation. The molecular weight of the polymer was controlled by the number of initiator radicals presented in the initial state and molecular weight effect to the density, the glass transition temperature, and the mechanical properties were studied.

Investigation on Chain Transfer Reaction of Benzene Sulfonyl Chloride in Styrene Radical Polymerization

  • Li, Cuiping;Fu, Zhifeng;Shi, Yan
    • Macromolecular Research
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    • v.17 no.8
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    • pp.557-562
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    • 2009
  • The free radical polymerization of styrene was initiated with azobis(isobutyronitrile) in the presence of benzene sulfonyl chloride. Analysis of the terminal structures of the obtained polystyrene with $^1H$ NMR spectroscopy revealed the presence of a phenyl sulfonyl group at the ${\alpha}$-end and a chlorine atom at the ${\omega}$-end of each polystyrene chain. The terminal chlorine atom in the polystyrene chains was further confirmed through atom transfer radical polymerization (ATRP) of styrene and methyl acrylate using the obtained polystyrenes as macroinitiators and CuCl/2,2'-bipyridine as the catalyst system. GPC traces of the products obtained in ATRP at different reaction times were clearly shifted to higher molecular weight direction, indicating that nearly all the macroinitiator chains initiated ATRP of the second monomers. In addition, the number-average molecular weights of the polystyrenes increased directly proportional to the monomer conversions, and agreed well with the theoretical ones.

Diacetylene Polymerize in Amorphous State? Free Radical Initiated Polymerization of Aromatic Diacetylenes.

  • Beristain Miriam F.;Ogawa Takeshi
    • Proceedings of the Polymer Society of Korea Conference
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    • pp.321-321
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    • 2006
  • Aromatic diacetylenes form stable oligomeric diradicals when irradiated with UV light or heated at temperatures above their melting points. In this paper, the formation of stable diradicals is discussed, and the mechanism of polymerization in the presence of peroxide in solution, is discussed. The diphenyldiacetylene undergoes polymerization through coupling of diradicals, and not by the successive addition of radical species.

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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.

A Novel Synthetic Route to Highly Cross-Linked Poly(alkylvinylether)s. Synthesis and Free Radical Polymerization of a Vinyl Ether Monomer Containing Electron Acceptors in Side Chain

  • 이주연;이현주;김무용
    • Bulletin of the Korean Chemical Society
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    • v.17 no.3
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    • pp.257-262
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    • 1996
  • p-(2-Vinyloxyethoxy)benzylidenemalononitrile 2 and methyl p-(2-vinyloxyethoxy)benzylidenecyanoacetate 3 was prepared by the condensation of p-(2-vinyloxyethoxy)benzaldehyde 1 with malononitrile or methyl cyanoacetate, respectively. Vinyl ether monomers 2 and 3 polymerized quantitatively with radical initiators in γ-butyrolactone solution at 65 ℃. The trisubstituted terminal double bond participated in the vinyl polymerization and radical polymerization of 2 and 3 led to swelling polymers 4 and 5 that were not soluble in common solvents due to cross-linking. Under the same polymerization conditions ethylvinyl ether polymerized well with model compounds of p-methoxybenzylidenemalononitrile 6 and methyl p-methoxybenzylidenecyanoacetate 7, respectively, to give 1:1 alternating copolymers 8 and 9 in high yields. Polymers 4 and 5 showed a thermal stability up to 300 ℃ without any characteristic Tg peaks in DSC thermograms. Alternating copolymers 8 and 9 were soluble in common solvents such as acetone and DMSO, and the inherent viscosities of the polymers were in the range of 0.36-0.74 dL/g. Films cast from acetone solution were cloudy and tough and Tg values obtained from DSC thermograms were in the range of 59-60 ℃.

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