Influence of a reversible addition–fragmentation chain transfer agent in the dispersion polymerization of styrene

Saikia, Prakash J.,Lee, Jung Min,Lee, Byung H.,Choe, Soonja Wiley Subscription Services, Inc., A Wiley Company 2007 Journal of polymer science Part A, Polymer chemist Vol.45 No.3

<P>Dispersion polymerization was applied to the controlled/living free-radical polymerization of styrene with a reversible addition–fragmentation chain transfer (RAFT) polymerization agent in the presence of poly(N-vinylpyrrolidone) and 2,2′-azobisisobutyronitrile in an ethanol medium. The effects of the polymerization temperature and the postaddition of RAFT on the polymerization kinetics, molecular weight, polydispersity index (PDI), particle size, and particle size distribution were investigated. The polymerization was strongly dependent on both the temperature and postaddition of RAFT, and typical living behavior was observed when a low PDI was obtained with a linearly increased molecular weight. The rate of polymerization, molecular weight, and PDI, as well as the final particle size, decreased with an increased amount of the RAFT agent in comparison with those of traditional dispersion polymerization. Thus, the results suggest that the RAFT agent plays an important role in the dispersion polymerization of styrene, not only reducing the PDI from 3.34 to 1.28 but also producing monodisperse polystyrene microspheres. This appears to be the first instance in which a living character has been demonstrated in a RAFT-mediated dispersion polymerization of styrene while the colloidal stability is maintained in comparison with conventional dispersion polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 348–360, 2007</P> <B>Graphic Abstract</B> <P>Dispersion polymerization was applied to the controlled/living free-radical polymerization of styrene with a reversible addition–fragmentation chain transfer polymerization (RAFT) agent in the presence of poly(N-vinylpyrrolidone) and 2,2′-azobisisobutyronitrile in an ethanol medium. The effects of the polymerization temperature and the postaddition of RAFT on the polymerization kinetics, molecular weight, polydispersity index, particle size, and particle size distribution were investigated and found to be strongly dependent on both the temperature and postaddition of RAFT. <img src='wiley_img/0887624X-2007-45-3-POLA21834-gra001.gif' alt='wiley_img/0887624X-2007-45-3-POLA21834-gra001'> </P>

Synthesis of star polymers via nitroxide mediated free-radical polymerization: A “core-first” approach using resorcinarene-based alkoxyamine initiators

Abraham, Sinoj,Choi, Jae Ho,Ha, Chang-Sik,Kim, Il Wiley Subscription Services, Inc., A Wiley Company 2007 Journal of polymer science Part A, Polymer chemist Vol.45 No.23

<P>The synthesis of new octafunctional alkoxyamine initiators for nitroxide-mediated radical polymerization (NMRP), by the derivatization of resorcinarene with nitroxide free radicals viz TEMPO and a freshly prepared phosphonylated nitroxide, is described. The efficiency of these initiators toward the controlled radical polymerization of styrene and tert-butyl acrylate is investigated in detail. Linear analogues of these multifunctional initiators were also prepared to compare and evaluate their initiation efficiency. The favorable conditions for polymerization were optimized by varying the concentration of initiators and free nitroxides, reaction conditions, etc., to obtain well-defined star polymers. Star polystyrene thus obtained were further used as macro-initiator for the block copolymerization with tert-butyl acrylate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5559–5572, 2007</P> <B>Graphic Abstract</B> <P>The synthesis of new octafunctional alkoxyamine initiators for nitroxide-mediated radical polymerization (NMRP), by the derivatization of resorcinarene with nitroxide free radicals viz TEMPO and a freshly prepared phosphonylated nitroxide, is described. The efficiency of these initiators towards the controlled radical polymerization of styrene and tert-butyl acrylate is investigated in detail. Linear analogues were also prepared to compare the initiation efficiency. The favorable conditions for polymerization were optimized by varying reaction parameters, to obtain well-defined star polymers. Star polystyrene thus obtained were further used as macroinitiator for the block copolymerization with tert-butyl acrylate. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]</P><P> <img src='wiley_img/0887624X-2007-45-23-POLA22302-gra001.gif' alt='wiley_img/0887624X-2007-45-23-POLA22302-gra001'> </P>

Nitroxide 매개 리빙라디칼 중합법에 의한 isoprene의 중합특성에 관한 연구

홍성철 ( Sung Chul Hong ) 한국고무학회 2009 엘라스토머 및 콤포지트 Vol.44 No.1

본 논문에서는 nitroxide 매개 리빙라디칼 중합법을 이용한 isoprene의 중합 특성에 관하여 연구하였다. 중합첨가제로 acetol이 첨가된 경우, 생성되는 고분자의 분자량이 전환율에 따라 직선적으로 증가하고, 제조된 고분자의 분자량 분포값이 1.5 이하의 값을 보임으로써, 성공적인 리빙라디칼 중합이 이루어졌음을 알 수 있었다. 제조된 poly-isoprene은 약 22%의 3,4구조, 약 30%의 1,4-cis구조, 약 48%의 1,4-trans 구조로 구성되어 있었다. 중합은 145℃에서 최선의 결과를 보였으며, 이보다 낮은 온도에서는 진행되지 않았다. Nitroxide의 경우, non-cyclic ni-troxide인 di-tert-butyl nitroxide(DTBN)의 경우 리빙라디칼 중합을 매개하지 못하였으나, 2,2,6,6-tetra-methyl-1-peperidine 1-oxyl (TEMPO)와 4-oxo-2,2,6,6-tetramethyl-1-peperidine 1-oxyl(oxoTEMPO)의 경우 성공적으로 리빙라디칼 중합을 매개하였다. 그러나, 주어진 중합조건 내에서 일부 isoprene은 Diels-Alder 이량화 반응(dimerization)에 의하여 고분자가 아닌 limonene 등으로 전환되는 것으로 관찰되었다. 주어진 중합조건하에서 isoprene의 자동열개시 반응도 가능하였으나, 별도의 중합개시제를 사용할 경우 그 정도는 무시할 수 있을 정도의 양인 것으로 판단되었다. In this study, investigation on the polymerization characteristics of isoprene through nitroxide mediated controlled/living radical polymerization techniques was attempted. In the presence of acetol, linear increase of isoprene conversion with time and low polydispersities of the resulting polymers (Mw/Mn<1.5) were observed, which suggest successful controlled/living radical polymerization of isoprene. The microstructure of the resulting polyisoprene was composed of ~22% of 3,4,~30% of 1,4-cis and~48% of 1,4-trans. The optimum polymerization temperature was 145℃, below which no significant polymerization behavior was observed. Non-cyclic nitroxide, such as di-tert-butyl nitroxide (DTBN) could not mediate the polymerization, whereas cyclic nitroxides (2,2,6,6-tetramethyl-1-peperidine 1-oxyl (TEMPO) and 4-oxo-2,2,6,6-tetramethyl-1-peperidine 1-oxyl (oxoTEMPO)) were successfully employed for the polymerization. However, isoprene dimerization reaction through Diels-Alder process was also observed at the given polymerization condition, which afforded a significant amount of limonene. Isoprene thermal autoinitiation was also possible, which was, however, considered to be not significant under the given polymerization condition.

요오드화 알킬 존재하의 비닐아세테이트의 조절된 라디칼중합

마석일,남혜인,한규찬,권순홍,Mah, Souk-Il,Nam, Hye-In,Han, Kyu-Chan,Kwon, Soon-hong 한국섬유공학회 2002 한국섬유공학회지 Vol.39 No.5

Radical polymerization behaviors of vinyl acetate (VAc), initiated by N, N-azobisisobuty-ronitrile(AIBN) in the presence of several alkyl iodides(RI) such as chloroiodomethane(CIM), iodoform, and tridecafluorohexyliodide(TDFHI) have been investigated. Living natu.e, i.e., a fairly good agreement between the number average degree of polymerization of the resulting polymer (DP$_{n}$) and the theoretical value, determined by the molar ratio of VAc and RI, which is based on the assumption that one polymer molecule is formed by one molecule of RI. A linear relationship is observed between % conversion and DP$_{n}$ is observed when the molar ratio of AIBN/RI is kept at 2. The MWD of the resulting polymer decreases as % conversion increases. Polymers having narrow molecular weight distrbution (DP$_{n}$DP$_{n}$ <1.5) are obtained in the late. stage of polymerization. However, experimental DP$_{n}$ values show deviation from the theoretical values in the early stage of polymerization. This leads us to the conclusion that the living nature of the system is ascribable to the stabilization of the active propagating radical species by rapid iodine exchange with RI followed by the establishment of equilibrium between the active propagating radical species and polymer having a dormant carbon-iodine terminal group. The factors resulting in the loss of the living nature have also been discussed in conjunction with the results obtained from photo-induced polymerization.erization.

Exploration of highly active bidentate ligands for iron (III)-catalyzed ATRP

Khan, Mohd Yusuf,Zhou, Jun,Chen, Xiangxiong,Khan, Abuzar,Mudassir, Hasan,Xue, Zhigang,Lee, Seung Woo,Noh, Seok Kyun Elsevier 2016 Polymer Vol.90 No.-

<P><B>Abstract</B></P> <P>Novel highly active substituted P-N ligands were found to be remarkably efficient for the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and butyl methacrylate (BMA). The reaction was catalyzed by a high oxidation state metal (FeX<SUB>3</SUB>) coupled with ethyl-2-bromoisobutyrate (EBriB) as an ATRP initiator. MMA polymerization was examined by the gradual addition of FeX<SUB>3</SUB> and the complete transformation of uncontrolled ATRP (PDI∼1.59) to a controlled polymerization system (PDI∼1.13) was observed. The polymerizations were well controlled with a linear increase in the mean molecular weight (<I>M</I> <SUB> <I>n</I> </SUB>) and monomer conversion reached up to 90% without complications. In the case of the DTBP ligand, the experimental molecular weights matched the theoretical values well and the PDIs were narrower (<1.2) compared to the other ligands. Furthermore, the potentially active catalyst (FeBr<SUB>3</SUB>/DTBP) was used successfully for the polymerization of MMA at a 50-ppm catalyst loading. The probable mechanism using FeX<SUB>3</SUB> without an external additive was also determined.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Uncontrolled polymerization system can be entirely changed to controlled system simply replacing Fe(II)X<SUB>2</SUB> by Fe(III)X<SUB>3</SUB> without any external additive. </LI> <LI> Active catalysts [Fe(III)X<SUB>3</SUB>] with new bidentate (N-P) ligands were explored for the polymerization of MMA, BMA and Styrene with ppm level of catalyst maintaining living character of polymer. </LI> <LI> In situ reduction of Fe(III) to Fe(II) was observed by P-N ligand mainly which was analyzed by UV/vis/NIR spectroscopy respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Three different hetero-chelate ligands possessing nitrogen (-N) and phosphorus (-P) were examined for iron-mediated ATRP of MMA, BMA and styrene. The kinetic studies showed ATRP trend during polymerization. Polymerizations using lower oxidation state metal (FeX<SUB>2</SUB>) showed uncontrolled behavior (like high molecular weight distribution ∼1.58 and constant molecular weight after 50% monomer conversion). However, complete transformation of uncontrolled to controlled polymerization was noticed while introducing deactivator (FeX<SUB>3</SUB>) to the polymerization system and best-controlled results found by employing (FeX<SUB>3</SUB>) only. The results obtained were compared and a probable mechanism was proposed.</P> <P>[DISPLAY OMISSION]</P>

O-Imino-Isourea 기반 Thermal Radical Initiator(TRI) 의 특성 및 응용 연구

김혜원,박영일,김범진,김순천,김진철,노승만,이동근,정현욱 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Radical initiator 를 사용하는 Radical Polymerization 기반의 고분자 합성은 다양한 분야에서 연구되어왔다. 그 중 자동차 코팅분야에서 사용되는 radical polymerization 공정은 최근 자동차 경량화, 에너지 절감, 친환경 문제 등이 대두되고, 자동차 차체의 재료가 금속에서 플라스틱으로 바뀌는 추세가 지속되고 있어 보다 낮은 온도에서 개시되는 개시제의 개발이 반드시 필요하다. 본 연구에서는 O-Imino-Isourea 기반의 신규 TRI 중 radical 이 생성되는 온도를 조절하기 위해 radical이 생성되는 결합인 N-O 결합에 연결된 moiety를 Linear type(n-Pen, n-Hex, n-Hep) 3종과 cyclic type (C-Pen, C-Hex, C-Hep) 3종씩 총 6종을 합성하였다. 신규 TRI 6종의 물질들의 initiation 온도, polymerization 특성 등을 다양한 방법으로 분석하였고, 실제 자동차 clear coating 의 사용 적합성에 대해서 알아보았다. 본 연구를 통해 얻은 다양한 결과를 토대로 신규 TRI 의 자동차 coating 에 대한 가능성과 다양한 연구의 가능성을 제안하고자 한다.

Synthesis of 9H-fluoren-9-yl benzodithioates and their application as reversible addition–fragmentation chain transfer agents in living radical polymerization of styrene

Yong Liu,Yu-Zi Jin,Chun-He Lee,Jian Huo,이연식 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.2

The reversible addition–fragmentation chain transfer (RAFT) polymerization is one of living radical polymerizations. In this study, four different 9H-fluoren-9-yl benzodithiolates (FBDTs) were synthesized,and used along with azobis(isobutyronitrile) (AIBN), a radical initiator, in polymerization of styrene (ST)at the molar ratio of 3:1. This new transfer agent exhibited the typical characteristic living free radical polymerization behaviors such as good control of molecule weight and narrow molecule weight distribution. It was concluded that the FBDTs can be used as the RAFT agents in free radical polymerization of vinyl monomers.

Phosphorus ligands for iron(III)-mediated ATRP of styrene via generation of activators by monomer addition

He, Dan,Xue, Zhigang,Khan, Mohd Yusuf,Noh, Seok Kyun,Lyoo, Won Seok Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of polymer science Part A, Polymer chemist Vol.48 No.1

<P>Styrene polymerization via generation of activators by monomer addition (GAMA) for atom transfer radical polymerization (ATRP) has been examined extensively with bulk FeX<SUB>3</SUB> and FeX<SUB>2</SUB> at 110 °C in conjunction with various phosphorus-bearing ligands. It was found that GAMA possesses advantages over normal ATRP. Most importantly, narrower polydispersity index (PDI) values were observed from the styrene polymerizations with Fe(III) over those with Fe(II). Every instance of 2-(diphenylphosphino)-N,N′-dimethyl-[1,1′-biphenyl]-2-amine and 2-(diphenylphosphino) pyridine with the Fe(III) system were controlled excellently without addition of any radical initiator or reducing agent additives. Initiator type was found to exert a significant factor to influence on the controllability of polymerization. The initiation of 1-phenylethyl chloride and methyl-2-chloropropionate gave rise to formation of polymers with narrow PDI (1.05–1.20), whereas those from 1-phenylethyl bromide increased to 1.35. The GAMA of bulk styrene exhibited the best performance in terms of both rate and controllability compared with toluene and anisole. Both formation of block copolymer from the macroinitiator and efficient perturbation of polymerization with 2,2,6,6-tetramethylpiperidine 1-oxyl provided firm evidence to support the living and radical characteristics for the GAMA of styrene. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 144–151, 2010</P> <B>Graphic Abstract</B> <P>Styrene polymerization with iron(III) complexes with various phosphorus-containing ligands via generation of activators by monomer addition (GAMA) for atom transfer radical polymerization (ATRP) in the absence of any additive, is herein reported as a new ATRP method. The polymers formed in the GAMA of styrene have better controlled molecular weights and narrower polydispersities than normal ATRP under same conditions. The use of oxidatively stable catalysts can avoid the air-sensitive properties of lower-oxidation-state metals, and in addition, styrene acts as a in situ reducing agent to generate activators (Iron(II) species) as is showed in this mechanism diagram of GAMA of styrene. All the advantages of GAMA make this novel ATRP method much easier for practical production. <img src='wiley_img/0887624X-2010-48-1-POLA23772-gra001.gif' alt='wiley_img/0887624X-2010-48-1-POLA23772-gra001'> </P>

Titanium Complexes: A Possible Catalyst for Controlled Radical Polymerization

Kwark, Young-Je,Kim, Jeong-Han,Novak Bruce M. The Polymer Society of Korea 2007 Macromolecular Research Vol.15 No.1

Pentamethylcyclopentadienyltitanium trichloride, bis(cyclopentadienyl)titanium dichloride ($Cp_2TiCl_2$), and bis(pentamethylcyclopentadienyl)titanium dichloride were used in the polymerization of styrene without the aid of Group I-III cocatalysts. The properties of the resulting polymer indicated that polymerization was more controlled than in thermal polymerization. The kinetic studies indicated that a lower level of termination is present and that the polymer chain can be extended by adding an additional monomer. To elucidate the mechanism of polymerization, a series of experiments was performed. All results supported the involvement of a radical mechanism in the polymerization using $Cp_2TiCl_2$. The possibility of atom transfer radical polymerization (ATRP) mechanism was investigated by isolating the intermediate species. We could confirm the activation step from the reaction of 1-PEC1 with $Cp_2TiCl$ by detecting the coupling product of the generated active radicals. However, the reversible deactivation reaction competes with other side reactions, and it detection was difficult with our model system.

Cu Catalyst System with Phosphorous Containing Bidendate Ligand for Living Radical Polymerization of MMA

Hong Sung Chul,Shin Ki Eun,Noh Seok Kyun,Lyoo Won Seok The Polymer Society of Korea 2005 Macromolecular Research Vol.13 No.5

The polymerization of methyl methacrylate (MMA) was carried out using CuBr/bidentate phosphorus ligand catalyst systems. MMA polymerization with CuBr/phosphine-phosphinidene (PP) exhibited high conversion ($\~80\%$) in 5 h at $90^{\circ}C$ along with a linear increase of ln($[M]_0/[M]$) versus time, indicating constant concentration of the propagating radicals during the polymerization. The molecular weight of the prepared PMMA tended to increase with conversion, suggesting the living polymerization characteristic of the system. On the other hand, a large difference between the measured and theoretical molecular weight and a broad molecular weight distribution were observed, implicating possible incomplete control over the polymerization. This may have been caused by the low deactivation rate constant ($\kappa_{deact}$) of the system. The low $\kappa_{deact}$, would result in irreversible generation of radicals instead of reversible activation/deactivation process of ATRP. Polymerizations performed at different ligand to CuBr ratios and different monomer to initiator ratios did not afford better control over the polymerization, suggesting that the controllability of CuBr/phosphorus ligand system for ATRP is inherently limited.