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>

Core-Shell Poly(Styrene/Sulfonated N-hydroxy Ethyl Aniline) Latex Particles Prepared by Chemical Oxidative Polymerization in Emulsion Polymerization

Shin Jin-Sup,Lee Jung-Min,Suzuki Kiyoshi,Nomura Mamoru,Cheong In-Woo,Kim Jung-Hyun The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.4

The kinetic behavior of emulsion polymerizations of styrene in the presence of sulfonated N-hydroxy ethyl aniline (SHEA) was investigated with two initiators: 2,2'-azobisisobutyronitrile (AIBN) and potassium persulfate (KPS). SHEA was synthesized using a stepwise polyurethane reaction method from 3-hydroxy-1-propane sulfonic acid sodium salt, isophorone diisocyanate (IPDI), and N-(2-hydroxyethyl) aniline. Stable core-shell poly(styrene/sulfonated N-hydroxy ethyl aniline, St/SHEA) latex particles were successfully prepared by using an appropriate amount of AIBN, in which SHEA plays the role of 'surfmer', i.e., acting as both a surfactant in the emulsion polymerization and a monomer in the chemical oxidative polymerization. The kinetic behavior was dissimilar to that of typical emulsion polymerization systems. A long inhibition period and low rate of polymerization were observed due to radical loss by the oxidative polymerization of SHEA. It was concluded, due to the low water-solubility of AIBN and retardation reaction by SHEA, that the initial loci of polymerization were monomer droplets. However, growing polymer particles as polymerization loci became predominant as polymerization proceeded. It was suggested that AIBN was more effective than KPS in the preparation of the core-shell type poly(St/SHEA) latex particles. With KPS, no substantial polymerization was observed in any of the samples.

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 The Polymer Society of Korea 2005 Macromolecular Research Vol.13 No.3

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.

TEMPO-mediated dispersion polymerization of styrene in the presence of camphorsulfonic acid

Oh, Sejin,Kim, Kijung,Lee, Byung H.,Shim, Sang Eun,Choe, Soonja Wiley Subscription Services, Inc., A Wiley Company 2006 Journal of polymer science Part A, Polymer chemist Vol.44 No.1

<P>The TEMPO-mediated polymerization of styrene in the presence of camphorsulfonic acid (CSA) is carried out using controlled radical dispersion polymerization. In the absence of TEMPO and CSA, 92% of conversion was achieved within 3 h of polymerization. When TEMPO is solely used, broadening of particle size with narrow PDI was observed because of the prolonged polymerization time. However, when 1:1 molar ratio of CSA/TEMPO was added, the fairly monodisperse PS microspheres having 5.83 μm average size and 3.42% C<SUB>V</SUB> (coefficient of variation) were successfully achieved because of the narrow molecular weight of intermediate oligomers and shortening of the polymerization time. This result obviously indicates that the addition of CSA in TEMPO-mediated dispersion polymerization not only shortens the polymerization time but also greatly improves the uniformity of the microspheres. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 62–68, 2006</P> <B>Graphic Abstract</B> <P>The TEMPO-mediated polymerization of styrene in the presence of camphorsulfonic acid (CSA) is carried out using controlled radical dispersion polymerization. The experimental result obviously indicates that the addition of CSA in TEMPO-mediated dispersion polymerization not only shortens the polymerization time but also greatly improves the uniformity of the microspheres. <img src='wiley_img/0887624X-2006-44-1-POLA20988-gra001.gif' alt='wiley_img/0887624X-2006-44-1-POLA20988-gra001'> </P>

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

오세진,김기정,고나래,심상은,최순자 한국고분자학회 2005 Macromolecular Research Vol.13 No.3

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 5.83m 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.

전자빔조사에 의한 HEMA의 중합과 소프트콘택트렌즈 제조

황광하,신중혁,성유진,정근승,전진 한국안광학회 2012 한국안광학회지 Vol.17 No.2

Purpose: Polymerization of HEMA(2-hydroxyethyl methacrylate) which can be used in the soft contact lens has been performed by using electron beam(EB) irradiation, and examined the best condition for the polymerization. Comparing the physical properties of the contact lenses to the one fabricated by thermal polymerization method,we check the use possibility of the EB irradiation to the fabrication of the soft contact lens. Methods: We investigated the degree of polymerization of the HEMA according to the composition of the monomer, the additive ratio and the dose of electron beam (0~120 kGy). The degree of polymerization was measured depending on the EB dose to research the best synthetic condition under the EB irradiation. The physical properties of the contact lens such as water content(%), oxygen transmissibility(Dk/t) and optical transmittance were analysed by using the FT-IR results with comparing the two different polymerization method (thermal and electron beam polymerization) with same additive ratio. Results: When the dose of electron beam was above 100 kGy, the degree of polymerization of HEMA was above 99% with regardless using cross-linker and initiator. The water content of the lens fabricated by EB method showed 10% higher than the one by the thermal method which was 40%. The lens fabricated by EB method also showed higher oxygen transmissibility(Dk/t) as same with the water content, and showed twice higher value in the lens fabricated by pure HEMA. According to the FT-IR results,hydrophilic property of the lens fabricated by EB method was increased due to increasing the intermolecular hydrogen bonding. It showed above 90% optical transmittance in the visible range of wavelength on the contact lenses fabricated by the both of two different polymerization method. Conclusions: The polymerization of HEMA without cross-linker and initiator was successful above 100 kGy of EB irradiation. Moreover the lens fabricated from the polymer synthesized by pure HEMA with 100 kGy of EB showed the highest water content and oxygen transmissibility. Therefore EB irradiation is another possible method to synthesize the polymer which can be used for the soft contact lens. 목적: 전자빔(electron beam)을 이용한 HEMA(2-hydroxyethyl methacrylate)의 중합과정에 대한 최적의 전자빔조사(irradiation) 조건을 살펴보고, 전자빔과 일반적인 열중합 방법에 의해 제조된 콘택트렌즈의 물리적 특성을 각각 비교함으로써 콘택트렌즈 제조에 전자빔조사 방법의 활용가능성을 알아보고자 한다. 방법: 중합에 사용된 모노머(monomer)나 첨가제의 구성비 그리고 전자빔흡수선량(0~120 kGy)에 따라 HEMA의 중합정도를 관찰하여 전자빔조사(irradiation)에 의한 중합여부와 최적의 중합조건을 제시하였다. 동일한 반응물 구성비에 대해 전자빔과 열중합의 두 가지 다른 중합방법을 이용하여 고분자를 합성하였다. 각각의 고분자로부터 제조된 소프트콘택트렌즈에 대해함수율, 산소전달률(Dk/t), 광투과율 등의 물리화학적 특성을 FT-IR 결과를 이용하여 비교 분석하였다. 결과: 전자빔조사선량(0~120 kGy)에 따라 살펴본 HEMA의 중합률은 100 kGy 이상에서 99% 이상으로 나타났으며, 사용된 모노머의 구성비나 광개시제와 가교제 등의 첨가에 무관하게 높은 중합률을 보였다. 전자빔 조사에 의해 제조된 렌즈의 함수율은 열중합 방법에 의해 제작된 렌즈에 비해 10% 이상 높게 나타났다. 산소전달률(Dk/t)도 함수율과 마찬가지로 전자빔조사방법에 의해 제조된 렌즈에서 더 높게 나타났으며, 순수한 HEMA의 경우는 약 2배 정도 높은 값을 보였다. FT-IR 분석결과, 전자빔 조사방법에 의해 제조한 렌즈에서 친수성 증가와 관계되는 OH group의 농도가증가하였고 이에 따른 분자간 수소결합의 농도가 증가함을 확인하였다. 두 가지 다른 중합방법에 의해 제조된 렌즈의 가시광선(380~800 nm) 영역에서 광 투과율은 제조방법과는 상관없이 유사하였으며, 90% 이상의 높은 값을 나타내었다. 결론: HEMA를 기본으로 구성된 다양한 반응혼합물과 개시제나 가교제의 첨가가 없는 순수한 HEMA에100kGy 이상의 전자빔을 조사할 경우 중합이 성공적으로 이루어졌다. 또한 순수한 HEMA에 100kGy의 전자빔을조사하여 중합된 고분자로부터 제조된 콘택트렌즈에서 가장 높은 함수율과 산소전달률을 나타내어 전자빔조사조건에 따라 물리적특성이 다른 콘택트렌즈의 제조가 가능함을 확인하였다.

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>

Late transition metal catalysis for olefin polymerization: New monomers and new materials

( Kohtaro Osakada ) 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.1

Molecular transition metal catalysis in synthetic organic reactions has long been studied as the media for production of various organic materials. Late transition metal catalysts for productive olefin polymerization were reported much later (1990’s), but they have advantages in smooth copolymerization of hydrocarbon olefins with functionalized vinyl-compounds. Recent studies on the polyolefin materials with new properties, including environmentally favorable ones. We have studied in the polymerization of new monomers, such as dienes, highly functionalized olefins, strained olefins, and sterically bulky olefins, suited for polymerization catalyzed by the Ni, Fe, Co, and Pd complexes. Homo- and co-polymerization of the new monomers provided the polymer materials, such as aliphatic liquid-crystalline polymers, a component of the physical gels that undergo a sol-gel transition at the definite temperature, highly-ordered polymers having small membered ring, etc. Use of double-decker type bimetallic complexes as the catalysts for the olefin polymerization enabled the reaction at higher temperatures than the reaction using mononuclear catalysts. It is caused by cooperative interaction of the two metal centers to the polymer backbone and its end group, which not only stabilize the polymer end group but enhance selective insertion of monomer molecules into the polymer-metal bond. The complexes have the shorter metal-metal bond than most of the recently reported dinuclear transition metal complexes for olefin polymerization, and their structure supported by the rigid macrocyclic ligands influences the polymerization in a positive fashion.

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.

아르곤 레이저를 이용한 광중합 수복재의 물리적 성질에 관한 연구

최형준,주상호,김성오,이종갑 大韓小兒齒科學會 1998 大韓小兒齒科學會誌 Vol.25 No.2

The purpose of this study is to evaluate and compare the results of argon laser for 5 seconds, argon laser for 10 seconds, and visible light for 40 seconds photo-polyerization in compressive strength, microhardness, curing depth, temperature rising during polymerization, and polymerization shrinkage. Hybrid type composite resin(Z-100) and compomer (Dyract) were used to be compared. The compressive strength was measured by an Instron (1mm/min cross head speed) in 60 specimens and the microhardness of the surface was expressed by Vickers Hardness Number (VHN) in 30 specimens. The curing depth was evaluated comparing the different values of upeer and lower VHN according to irradiation time and thickness for the light sourece polymeriaztion in 60 specimens. the temperature rising during photopolymerization was observed by the temperature change with thermocouple sensitizer beneath 40 specimens at th argon laser for 10 seconds and visible light 40 seconds irradiation. the polymerization shinkage was evaluated by calculating the decrease of % volume by using a dilatometer in 30 specimens. The results were as follows : 1. In the case of compressive strength, the argon laser polymerization groups were higher than visible light group in Z-100 (p<0.05). In Dyract, the argon laser 5 seconds group did not show a significant difference with the visible light 40 seconds group. The argon laser 10 seconds group showed the markedly low value when compared with other g개ups (p<0.05) 2. In micriohardness, Z-100 was better than Dyract when comparing by VHNs(p<0.05) ; however, there was not a significant difference between two materials in the visible light 40 seconds group and the argon laser 10 seconds groups. 3. In the study of curing depth, Z-100 showed the consistent polymerization in argon laser irradiation because there was no difference in the VHN decrease according to the thickness change. Over the thickness control, the results did not show a significant difference between visible light and argon laser group in Z-100 ; however, in the case of Dyrct, the visible light 40 seconds group was better than the argon laser groups(p<0.05). 4. There was a significant difference between the two materials in temperature rising during polymerization (p<0.05), but not a significant difference between irradiation times. 5. There was not a significant difference between the two materials in polymerization shrink-age. The argon laser 5 seconds group was smaller than the other groups (p<0.05). It could be concluded that z-100 polymerization was recommended to use the argon laser for reduction of the irradiation time while Dyract was recommended to use the visible light polymerization.