共查询到20条相似文献,搜索用时 31 毫秒
1.
Michael F. Cunningham David C. T. Ng Sarah G. Milton Barkev Keoshkerian 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):232-242
The 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)‐mediated stable free radical polymerization of styrene in miniemulsion at 100 °C is demonstrated. Although this temperature is 20–35 °C lower than typical temperatures used for TEMPO‐mediated polymerizations, reasonable reaction rates were achieved by the addition of ascorbic acid or a free radical initiator. More importantly, the living character of the chains was preserved; the degree of polymer “livingness” was comparable to polymerizations conducted at 135 °C. Polydispersities were broader than that observed in well‐controlled systems, ranging from ~1.4–1.6, and consistent with expectations for systems having a low activation rate. The results are significant for two reasons. They will facilitate TEMPO‐mediated minemulsion polymerizations in nonpressurized (or minimally pressurized) reactors, and they reveal the potential to expand the traditional temperature range of TEMPO and possibly other nitroxides in bulk, solution, and miniemulsion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 232–242, 2006 相似文献
2.
Steven C. Farmer Timothy E. Patten 《Journal of polymer science. Part A, Polymer chemistry》2002,40(4):555-563
Ethyl S‐(thiobenzoyl)thioacetate, ethyl S‐thiobenzoyl‐2‐thiopropionate, and S‐(thiobenzoyl)thioglycolic acid were used as chain‐transfer agents for the reversible addition–fragmentation chain‐transfer (RAFT) polymerizations of styrene, methyl methacrylate, and butyl acrylate. Of these polymerizations, only those of styrene and butyl acrylate with any of the transfer agents showed molecular weight control corresponding to controlled/living polymerizations. The best molecular weight control was observed for the polymerizations of styrene and butyl acrylate with ethyl (S)‐thiobenzoyl‐2‐thiopropionate. Semiempirical PM3 calculations were performed for the investigation of the relative heats of reaction of the chain‐transfer equilibria between the aforementioned chain‐transfer agents and dimer radicals of the three monomers. The molecular weight control of the polymerizations correlated with the stability trend of the leaving‐group radical of the chain‐transfer agent. This relatively simple computational model offered some value in determining which transfer agents would show the best molecular weight control in RAFT polymerizations. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 555–563, 2002; DOI 10.1002/pola.10143 相似文献
3.
Masami Kamigaito Kotaro Satoh Mineto Uchiyama 《Journal of polymer science. Part A, Polymer chemistry》2019,57(3):243-254
The use of dormant species has opened a new era in precision polymerization and has changed the concept of living polymerization. The dormant species can be exchanged into the active species via reversible termination or via reversible chain transfer. Professor Mitsuo Sawamoto has greatly contributed to the establishment of the concepts of living cationic and radical polymerizations based on the reversible activation of dormant species. This highlight, dedicated to Professor Sawamoto on his retirement from Kyoto University, provides an overview of reversible or degenerative chain‐transfer (DT) processes, which are effective in controlling all chain‐growth polymerizations, including radical, cationic, anionic, coordination, ring‐opening metathesis, and ring‐opening polymerizations. In addition, structures with novel sequences accessible only by a combination of different propagating species with a common DT agent are reviewed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 243–254 相似文献
4.
Xiao‐Hui Liu Gui‐Bao Zhang Bai‐Xiang Li Yun‐Gang Bai Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2010,48(23):5439-5445
Cu(0)‐mediated living radical polymerization was first extended to acrylonitrile (AN) to synthesize polyacrylonitrile with a high molecular weight and a low polydispersity index. This was achieved by using Cu(0)/hexamethylated tris(2‐aminoethyl)amine (Me6‐TREN) as the catalyst, 2‐bromopropionitrile as the initiator, and dimethyl sulfoxide (DMSO) as the solvent. The reaction was performed under mild reaction conditions at ambient temperature and thus biradical termination reaction was low. The rapid and extensive disproportionation of Cu(I)Br/Me6‐TREN in DMSO/AN supports a mechanism consistent with a single electron transfer‐living radical polymerization (SET‐LRP) rather than activators generated by electron transfer atom transfer radical polymerization (AGET ATRP). 1H NMR analysis and chain extension experiment confirm the high chain‐end functionality of the resultant polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
5.
Virgil Percec Ernesto Ramirez‐Castillo Anatoliy V. Popov Luis A. Hinojosa‐Falcon Tamaz Guliashvili 《Journal of polymer science. Part A, Polymer chemistry》2005,43(10):2178-2184
Sodium dithionite in the presence of NaHCO3 in water acts as a single‐electron‐transfer agent and facilitates the single‐electron‐transfer/degenerative‐chain‐transfer mediated living radical polymerization (SET–DTLRP) of acrylates initiated with iodoform at room temperature. The resulting α,ω‐di(iodo)polyacrylates can be used as macroinitiators for the SET–DTLRP of other acrylates. Ultrahigh‐molar‐mass poly(tert‐butyl acrylate) can be synthesized via the SET–DTLRP of tert‐butyl acrylate and has a very low weight‐average molecular weight/number‐average molecular weight ratio of 1.15. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2178–2184, 2005 相似文献
6.
Wenxiang Wang Zhengbiao Zhang Yang Wu Jian Zhu Zhenping Cheng Nianchen Zhou Wei Zhang Xiulin Zhu 《Journal of polymer science. Part A, Polymer chemistry》2012,50(4):711-719
For the first time, ligand‐free Cu(0)‐mediated polymerization of methyl methacrylate (MMA) was realized by the selection of ethyl‐2‐bromo‐2‐phenylacetate as initiator at ambient temperature. The polymerization can reach up to 90% conversion within 5 h with dimethyl sulfoxide (DMSO) as solvent, while keeping manners of the controlled radical polymerization. Extensive investigation of this system revealed that for a well‐controlled Cu(0)‐mediated polymerization of MMA, the initiator should be selected with the structure as alkyl 2‐bromo‐2‐phenylacetate, and the solvent should be DMSO or N,N‐dimethylformamide. The selectivity for solvents indicated a typical single‐electron transfer‐living radical polymerization process. Scanning for other monomers indicated that under equal conditions, the polymerizations of other alkyl (meth)acrylates were uncontrollable. Based on these results, plausible reasons were discussed. The ligand‐free Cu(0)‐mediated polymerization showed its superiority with economical components and needless removal of Cu species from the resultant products. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
7.
Liangjiu Bai Lifen Zhang Jian Zhu Zhenping Cheng Xiulin Zhu 《Journal of polymer science. Part A, Polymer chemistry》2009,47(8):2002-2008
A commercially available tris(3,6‐dioxaheptyl)amine (TDA‐1) was used as a novel ligand for activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) of styrene in bulk or solution mediated by iron(III) catalyst in the presence of a limited amount of air. FeCl3 · 6H2O and (1‐bromoethyl)benzene (PEBr) were used as the catalyst and initiator, respectively; and environmentally benign ascorbic acid (VC) was used as the reducing agent. The polymerizations show the features of “living”/controlled free‐radical polymerizations and well‐defined polystyrenes with molecular weight Mn = 2400–36,500 g/mol and narrow polydispersity (Mw/Mn = 1.11–1.29) were obtained. The “living” feature of the obtained polymer was further confirmed by a chain‐extension experiment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2002–2008, 2009 相似文献
8.
Gennady S. Ananchenko Marc Souaille Hanns Fischer Christophe Le Mercier Paul Tordo 《Journal of polymer science. Part A, Polymer chemistry》2002,40(19):3264-3283
Thermal reactions of the alkoxyamine diastereomers DEPN‐R′ [DEPN: N‐(2‐methylpropyl)‐N‐(1‐diethylphosphophono‐2,2‐dimethyl‐propyl)‐aminoxyl; R′: methoxy‐carbonylethyl and phenylethyl] with (R,R) + (S,S) and (R,S) + (S,R) configurations have been investigated by 1H NMR at 100 °C. During the overall decay the diastereomers interconvert, and an analytical treatment of the combined processes is presented. Rate constants are obtained for the cleavage and reformation of DEPN‐R′ from NMR, electron spin resonance, and chemically induced dynamic nuclear polarization experiments also using 2,2,6,6‐tetramethylpiperidinyl‐1‐oxyl (TEMPO) as a radical scavenger. The rate constants depend on the diastereomer configuration and the residues R′. Simulations of the kinetics observed with styrene and methyl methacrylate containing solutions yielded rate constants for unimeric and polymeric alkoxyamines DEPN‐(M)n‐R′. The results were compatible with the known DEPN mediation of living styrene and acrylate polymerizations. For methyl methacrylate the equilibrium constant of the reversible cleavage of the dormant chains DEPN‐(M)n‐R′ is very large and renders successful living polymerizations unlikely. Mechanistic and kinetic differences of DEPN‐ and TEMPO‐mediated polymerizations are discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3264–3283, 2002 相似文献
9.
Chunzhao Li Brian C. Benicewicz 《Journal of polymer science. Part A, Polymer chemistry》2005,43(7):1535-1543
A series of new reversible addition–fragmentation chain transfer (RAFT) agents with cyanobenzyl R groups were synthesized. In comparison with other dithioester RAFT agents, these new RAFT agents were odorless or low‐odor, and this made them much easier to handle. The kinetics of methyl methacrylate radical polymerizations mediated by these RAFT agents were investigated. The polymerizations proceeded in a controlled way, the first‐order kinetics evolved in a linear fashion with time, the molecular weights increased linearly with the conversions, and the polydispersities were very narrow (~1.1). A poly[(methyl methacrylate)‐block‐polystyrene] block copolymer was prepared (number‐average molecular weight = 42,600, polydispersity index = 1.21) from a poly(methyl methacrylate) macro‐RAFT agent. These new RAFT agents also showed excellent control over the radical polymerization of styrenics and acrylates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1535–1543, 2005 相似文献
10.
Qin Zhang Zhengbiao Zhang Wenxiang Wang Jian Zhu Zhenping Cheng Nianchen Zhou Wei Zhang Xiulin Zhu 《Journal of polymer science. Part A, Polymer chemistry》2012,50(7):1424-1433
In this work, cupric oxide (CuO) or cuprous oxide (Cu2O) was used as the catalyst for the single electron transfer‐reversible addition‐fragmentation chain transfer (SET‐RAFT) polymerization of methyl methacrylate in the presence of ascorbic acid at 25 °C. 2‐Cyanoprop‐2‐yl‐1‐dithionaphthalate (CPDN) was used as the RAFT agent. The polymerization occurred smoothly after an induction period arising from the slow activation of CuO (or Cu2O) and the “initialization” process in RAFT polymerization. The polymerizations conveyed features of “living”/controlled radical polymerizations: linear evolution of number‐average molecular weight with monomer conversion, narrow molecular weight distribution, and high retention of chain end fidelity. From the polymerization profile, it was deduced that the polymerization proceeded via a conjunct mechanism of single electron transfer‐living radical polymerization (SET‐LRP) and RAFT polymerization, wherein CPDN acting as the initiator for SET‐LRP and chain transfer agent for RAFT polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
11.
Per B. Zetterlund Fawaz Aldabbagh Masayoshi Okubo 《Journal of polymer science. Part A, Polymer chemistry》2009,47(15):3711-3728
Supercritical carbon dioxide (scCO2) is an inexpensive and environmentally friendly medium for radical polymerizations. ScCO2 is suited for heterogeneous controlled/living radical polymerizations (CLRPs), since the monomer, initiator, and control reagents (nitroxide, etc.) are soluble, but the polymer formed is insoluble beyond a critical degree of polymerization (Jcrit). The precipitated polymer can continue growing in (only) the particle phase giving living polymer of controlled well‐defined microstructure. The addition of a colloidal stabilizer gives a dispersion polymerization with well‐defined colloidal particles being formed. In recent years, nitroxide‐mediated polymerization (NMP), atom transfer radical polymerization (ATRP), and reversible addition fragmentation chain transfer (RAFT) polymerization have all been conducted as heterogeneous polymerizations in scCO2. This Highlight reviews this recent body of work, and describes the unique characteristics of scCO2 that allows composite particle formation of unique morphology to be achieved. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3711–3728, 2009 相似文献
12.
Shengsheng Liu Ayusman Sen 《Journal of polymer science. Part A, Polymer chemistry》2004,42(24):6175-6192
The living/controlled copolymerization of methyl acrylate with 1‐alkenes and norbornene derivatives through several radical polymerization techniques has been achieved. These techniques include atom transfer radical polymerization, reversible addition–fragmentation transfer polymerization, nitroxide‐mediated polymerization, and degenerative transfer polymerization. These systems display many of the characteristics of a living polymerization process: the molecular weight increases linearly with the overall conversion, but the polydispersity remains low. Novel block copolymers have been synthesized through the sequential addition of monomers or chain extension. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6175–6192, 2004 相似文献
13.
Fei Ma Jian Zhu Zhengbiao Zhang Xiangqiang Pan Nianchen Zhou Xiulin Zhu 《Journal of polymer science. Part A, Polymer chemistry》2013,51(15):3159-3165
The living free radical polymerizations of vinyl acetate (VAc) were successfully achieved in the presence of a novel organic selenium compound (diselenocarbonates), with 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. The living characteristics of the VAc polymerization were confirmed by the linear first‐order kinetic plots and linear increase of molecular weights (Mn) of the polymers with monomer conversions, while keeping the relatively low molecular weight distributions. In addition, the end of the polymers contains selenium element which may be useful in biotechnological and biomedical applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3159–3165 相似文献
14.
Marcus Lin James C. C. Hsu Michael F. Cunningham 《Journal of polymer science. Part A, Polymer chemistry》2006,44(20):5974-5986
In studying 2,2,6,6‐tetramethy‐1‐piperidinyloxy (TEMPO)‐mediated styrene miniemulsions, we have observed that the surfactant sodium dodecylbenzenesulfonate (SDBS) not only provides colloidal stability but also influences the rate of polymerization. Increasing the SDBS concentration results in higher polymerization rates, although the molecular weight distribution and particle size distribution are not significantly impacted. We have also examined another common sulfonate surfactant, DOWFAX 8390. In contrast to SDBS, DOWFAX 8390 does not affect the polymerization rate. Furthermore, DOWFAX‐stabilized polymerizations are slower than SDBS‐stabilized polymerizations. TEMPO‐mediated bulk styrene polymerizations are also accelerated significantly in the presence of SDBS. Although the mechanism for the rate acceleration is unknown, the experimental evidence suggests that SDBS is participating in the generation of radicals capable of propagating, thereby reducing the TEMPO concentration within the particles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5974–5986, 2006 相似文献
15.
Xiao‐Hui Liu Yan‐Guo Li Ying Lin Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2007,45(7):1272-1281
The reversible addition–fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2‐cyanoprop‐2‐yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANs were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. 1H NMR analysis confirmed the high chain‐end functionality of the resultant polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1272–1281, 2007 相似文献
16.
Living radical polymerization of diisopropyl fumarate to obtain block copolymers containing rigid poly(substituted methylene) and flexible polyacrylate segments
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Living radical polymerizations of diisopropyl fumarate (DiPF) are carried out to synthesize poly(diisopropyl fumarate) (PDiPF) as a rigid poly(substituted methylene) and its block copolymers combined with a flexible polyacrylate segment. Reversible addition‐fragmentation chain transfer (RAFT) polymerization is suitable to obtain a high‐molecular‐weight PDiPF with well‐controlled molecular weight, molecular weight distribution, and chain‐end structures, while organotellurium‐mediated living radical polymerization (TERP) and reversible chain transfer catalyzed polymerization (RTCP) give PDiPF with controlled chain structures under limited polymerization conditions. In contrast, controlled polymerization for the production of high‐molecular‐weight and well‐defined PDiPF is not achieved by atom transfer radical polymerization (ATRP) and nitroxide‐mediated radical polymerization (NMP). The block copolymers consisting of rigid poly(substituted methylene) and flexible polyacrylate segments are synthesized by the RAFT polymerization. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2136–2147 相似文献
17.
Gennady S. Ananchenko Hanns Fischer 《Journal of polymer science. Part A, Polymer chemistry》2001,39(20):3604-3621
The thermal decomposition of five alkoxyamines labeled TEMPO–R, where TEMPO was 2,2,6,6‐tetramethylpiperidinyl‐N‐oxyl and R was cumyl (Cum), 2‐tert‐butoxy‐carbonyl‐2‐propyl (PEst), phenylethyl (PhEt), 1‐tert‐butoxy‐carbonylethyl (EEst), or 1‐methoxycarbonyl‐3‐methyl‐3‐phenylbutyl (Acrylate‐Cum), was studied with 1H NMR in the absence and presence of styrene and methyl methacrylate. The major products were alkenes and the hydroxylamine 1‐hydroxy‐2,2,6,6‐tetramethyl‐ piperidine (TEMPOH), and in monomer‐containing solutions, unimeric and polymeric alkoxyamines and alkenes were also found. Furthermore, the reactions between TEMPO and the radicals EEst and PEst were studied with chemically induced dynamic nuclear polarization. In comparison with coupling, TEMPO reacted with the radicals Cum, PEst, PhEt, and EEst and their unimeric styrene adducts by disproportionation to alkenes and TEMPOH only to a minor extent (0.6–3%) but with the radical adducts to methyl methacrylate to a considerable degree (≥20%). Parallel to the radical cleavage, TEMPO–EEst (but not the other alkoxyamines or TEMPO–Acrylate‐Cum) underwent substantial nonradical decay. The consequences for TEMPO‐mediated living radical polymerizations are discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3604–3621, 2001 相似文献
18.
David H. Solomon 《Journal of polymer science. Part A, Polymer chemistry》2005,43(23):5748-5764
The background to the formation of the Commonwealth Scientific and Industrial Research Organization (CSIRO) polymer group is discussed. In particular, the challenges of working with high‐conversion polymerization, as found in commercial systems, and the need to explain variations in polymer properties led to important advances in the theory of radical polymerization and control over both the initiation and termination steps. Studies on the fate of the macromonomer, formed in termination by disproportionation, led to an early form of addition/fragmentation now known as reversible addition–fragmentation chain transfer, whereas detailed studies on initiation pathways using nitroxide trapping led to nitroxide‐mediated living radical polymerization. These studies contributed to the renaissance in free‐radical polymerization studies. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5748–5764, 2005 相似文献
19.
Wenxiang Wang Junfei Zhao Wei Zhang Jian Zhu Zhengbiao Zhang Xiulin Zhu 《Journal of polymer science. Part A, Polymer chemistry》2013,51(8):1872-1879
An iodine‐based initiator, 2‐iodo‐2‐methylpropionitrile (CPI), was utilized for the single‐electron transfer and degenerative chain transfer mediated living radical polymerization (SET‐DTLRP) of methyl methacrylate (MMA) in the absence of ligand, at ambient temperature. The CPI‐initiated ligand‐free polymerizations manifested reasonable control over molecular weights with relatively narrow distributions (Mw/Mn ≤ 1.35). The living nature of the polymers was further confirmed by successful chain extension reaction and 1H NMR with high chain‐end fidelity (~96%). Screening of the available solvents suggested that the controllability of this polymerization was highly dependent on the kind of solvents, wherein dimethyl sulfoxide was a better solvent for a controlled molecular weight. The proposed ligand‐free SET‐DTLRP initiated by CPI was intriguing since it would dramatically decrease the concentration of Cu(0) ions both in polymerization system and resultant polymer, and provided a more economical and eco‐friendly reversible‐deactivation radical polymerization technique. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
20.
Gerard Lligadas Virgil Percec 《Journal of polymer science. Part A, Polymer chemistry》2008,46(10):3174-3181
The Cu(0)/Me6‐TREN‐catalyzed single‐electron transfer mediated living radical polymerization (SET‐LRP) of methyl acrylate in the presence of the classic 4‐methoxyphenol free radical inhibitor was investigated. Kinetic experiments, combined with 1H NMR, and MALDI‐TOF MS analysis of the resulting polyacrylates demonstrated that SET‐LRP is a robust synthetic method that does not require the purification of the monomers to remove the radical inhibitor. It is anticipated that these results will contribute to the expansion of technological and fundamental applications of SET‐LRP since it allows the synthesis of polymers with a structural perfection that previously was not accessible by any other method, starting from unpurified monomers, solvents, initiators, and ligands. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3174–3181, 2008 相似文献