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1.
The development of Cu(0)/TREN/CuBr2‐catalyzed SET‐LRP of VC initiated with CHBr3 in DMSO at 25 °C is reported. The use of CuBr2 additive allows for the first LRP of low molecular weight VC (target DP = 100), as well as lower Cu powder loading levels, improved Ieff and control in the synthesis of higher molecular VC, targeted degree of polymerization = 350, 700, 1,000, 1,400. 1H NMR and HSQC confirm the bifunctionality of CHBr3 as an initiator and suggest that deleterious side‐reactions such as the formation of allylic chlorides occur primarily at the onset of the reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4130–4140, 2009  相似文献   

2.
The effect of initial ligand concentration on the apparent rate constant of propagation of single‐electron transfer living radical polymerization (SET‐LRP) of MA in DMSO at 25 °C was examined using various lengths of Cu(0) wire as catalyst. It was determined that unlike other parameters such as initiator concentration, solvent concentration, and deactivator concentration, no simple external rate‐order for the ligand concentration could be determined. Rather, the response of the rate of SET‐LRP to initial ligand concentration is complex and is likely determined by a competition of ligand‐dependent extent of disproportionation as well as the role of ligand concentration in the surface mediated activation process. Results suggest that a minimum concentration of ligand is needed to achieve both acceptable reaction rate and reaction control, and therefore, ligand concentration must be considered in designing experimental conditions for SET‐LRP. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5629–5638, 2009  相似文献   

3.
Single electron transfer‐living radical polymerization (SET‐LRP) of methyl acrylate (MA) in methanol, catalyzed with nonactivated and activated Cu(0) wires, was performed in the presence of nondeoxygenated reagents and was investigated under a simple blanket of nitrogen. The addition of a small amount of hydrazine hydrate mediates the deoxygenation of the reaction mixture by the consumption of oxygen through its use to oxidize Cu(0) to Cu2O, followed by the reduction of Cu2O with hydrazine back to the active Cu(0) catalyst. SET‐LRP of MA in methanol in the presence of air requires a smaller dimension of Cu(0) wire, compared to the nonactivated Cu(0) wire counterpart. Activation of Cu(0) wire allowed the polymerization in air to proceed with no induction period, linear first‐order kinetics, linear correlation between the molecular weight evolution with conversion, and narrow molecular weight distribution. The retention of chain‐end functionality of α,ω‐di(bromo) poly(methyl acrylate) (PMA) prepared by SET‐LRP was demonstrated by a combination of experiments including 1H NMR spectroscopy and matrix‐assisted laser desorption ionization–time of flight mass spectrometry after thioetherification of α,ω‐di(bromo) PMA with thiophenol. In SET‐LRP of MA in the presence of limited air, bimolecular termination is observed only above 85% conversion. However, for bifunctional initiators, the small amount of bimolecular termination observed at high conversion maintains a perfectly bifunctional polymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

4.
The new SET‐LRP (using Cu(0) powder for organic synthesis) was successfully used to produce well‐defined linear and star homo‐ and diblock‐copolymers of PMA, PSA, and P(MA‐b‐GA)n (where n = 1 or 4). The kinetic data showed that all SET‐LRP were first order and reached high conversions in a short period of time. The other advantage of using such a system is that the copper can easily be removed through filtration, allowing the production of highly pure polymer. The molecular weight distributions were well controlled with polydispersity indexes below 1.1 and the number‐average molecular weight close to theory, especially upon the addition of Cu(II)Br2/Me6‐TREN complex. The linear and star block copolymers were then hydrolyzed to produce the biocompatible amphiphilic P(MA‐b‐GA)n, where the glycerol side‐groups make the outer block hydrophilic. These blocks were micellized into water and found to have a Rg/RH equal to 0.8 and 1.59 for the liner and star blocks, respectively. This together with the TEM's supported that the linear blocks formed the classical core‐shell micelles, where as, the star blocks formed vesicles. We found direct support for the vesicle structure from a TEM where one vesicle squashed a second vesicle consistent with a hollow structure. Such vesicle structures have potential applications as delivery nanoscaled devices for drugs and other important biomolecules. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6346–6357, 2008  相似文献   

5.
The single‐electron transfer living radical polymerization (SET‐LRP) of methyl acrylate initiated with bromoform (CHBr3) and iodoform (CHI3) and catalyzed by Cu(0)/Me6‐TREN in DMSO at 25 °C provides a reliable method to prepare poly (methyl acrylate) (PMA) with active chain ends and controlled structure that can undergo subsequent functionalization to provide strategies for the synthesis of different block copolymers and other complex architectures. A detailed kinetic and structural analysis was used to assess the scope and the limitations of CHBr3 and CHI3 as initiators under SET‐LRP conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 278–288, 2008  相似文献   

6.
Alcohols are known to promote the disproportionation of Cu(I)X species into nascent Cu(0) and Cu(II)X. Therefore, alcohols are expected to be excellent solvents that facilitate the single‐electron transfer mediated living radical polymerization (SET‐LRP) mediated by nascent Cu(0) species. This publication demonstrates the ultrafast SET‐LRP of methyl acrylate initiated with bis(2‐bromopropionyloxy)ethane and catalyzed by Cu(0)/Me6‐TREN in methanol, ethanol, 1‐propanol, and tert‐butanol and in their mixture with water at 25 °C. The structural analysis of the resulting polymers by a combination of 1H NMR and MALDI‐TOF MS demonstrates the synthesis of perfectly bifunctional α,ω‐dibromo poly(methyl acrylate)s by SET‐LRP in alcohols. Moreover, this work provides an expansion of the list of solvents available for SET‐LRP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2745–2754, 2008  相似文献   

7.
Single electron transfer‐living radical polymerization (SET‐LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with defined architecture. The present article describes the polymerization of methyl methacrylate by SET‐LRP in protic solvent mixtures. Herein, the polymerization process was catalyzed by a straightforward Cu(0)wire/Me6‐TREN catalyst while initiation was obtained by toluenesulfonyl chloride. All experiments were conducted at 50 °C and the living polymerization was demonstrated by kinetic evaluation of the SET‐LRP. The process follows first order kinetic until all monomer is consumed which was typically achieved within 4 h. The molecular weight increased linearly with conversion and the molecular weight distributions were very narrow with Mw/Mn ~ 1.1. Detailed investigations of the polymer samples by MALDI‐TOF confirmed that no termination took place and that the chain end functionality is retained throughout the polymerization process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2236–2242, 2010  相似文献   

8.
In this work, single electron transfer‐living radical polymerization (SET‐LRP) was catalyzed by in situ Cu(0) generated from copper sulphate pentahydrate (CuSO4·5H2O) and hydrazine hydrate (N2H4·H2O) at 25 °C. The polymerization occurred smoothly with moderate controllability: the polymerization rates increased by the increases of N2H4·H2O, and the initiator concentration had an optimal value on the polymerization rate; the number‐average molecular weights (Mn,GPC) increased with monomer conversions and polydispersities were below 1.40. The Mn,GPC deviated much from theoretical ones with about 50% polymer chain‐end fidelities. Some side reactions stemming from the strong reduction performance of N2H4·H2O were responsible for the mildly controlled polymerizations. This polymerization can be conducted in SET‐LRP unfavorable solvents or in bulk, such as toluene and tetrahydrofuran, owing to the H2O contained in CuSO4·5H2O and N2H4·H2O. On account of the utilization of CuSO4·5H2O, an inactive Cu(II) compounds in LRP area, this work confirmed from experimental level that it was Cu(0) which acted as activator and mediator in SET‐LRP. This work provided a first example of in situ Cu(0) catalyzing SET‐LRP with CuSO4·5H2O as a copper source. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

9.
Sn(0)‐mediated single electron transfer‐living radical polymerization (SET‐LRP) of acrylonitrile (AN) with carbon tetrachloride (CCl4) as initiator and hexamethylenetetramine (HMTA) as ligand in N, N‐dimethylformamide (DMF) was studied. The polymerization obeyed first order kinetic. The molecular weight of polyacrylonitrile (PAN) increased linearly with monomer conversion and PAN exhibited narrow molecular weight distributions. Increasing the content of Sn(0) resulted in an increase in the molecular weight and the molecular weight distribution. Effects of ligand and initiator were also investigated. The block copolymer PAN‐b‐polymethyl methacrylate with molecular weight at 126,130 and polydispersity at 1.36 was successfully obtained. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

10.
Here we reported the acid dissolution of copper oxides as a methodology for the activation of Cu(0) wire used as catalyst in single‐electron transfer living radical polymerization (SET‐LRP). In this method, the oxide layer on the surface of commercial Cu(0) wire was removed by dissolution in a concentrated acid such as nitric acid, glacial acetic acid and hydrochloric acid. SET‐LRP of methyl acrylate catalyzed with Cu(0) wire activated with acids showed comparable k value to that of the nonactivated Cu(0) wire‐catalyzed counterpart. However, the polymerizations catalyzed with activated Cu(0) wire proceeded with no initial induction period, predictable molecular weight evolution with conversion, and narrow molecular weight distribution. Regardless of the activation method, the chain end functionality of α,ω‐di(bromo) poly(methyl acrylate) (PMA) prepared from SET‐LRP initiated with a bifunctional initiator is extremely high, maintaining a 100% chain end functionality at ~90% monomer conversion. The degree of bimolecular termination increased as the polymerization exceeds 92% conversion. However, for binfunctional initiators this small amount of bimolecular termination at high conversion maintains a perfectly bifunctional polymer. Structural analysis by MALDI‐TOF upon thioetherification of α,ω‐di(bromo) PMA with thiophenol and 4‐fluorothiophenol confirmed the high fidelity of bromide chain ends. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

11.
A simple method for the activation of the Cu(0) wire used as catalyst in single‐electron transfer living radical polymerization (SET‐LRP) is reported. The surface of Cu(0) stored in air is coated with a layer of Cu2O. It is well established that Cu2O is a less reactive catalyst for SET‐LRP than Cu(0). We report here the activation of the Cu(0) wire under nitrogen by the reduction of Cu2O from its surface to Cu(0) by treatment with hydrazine hydrate. The kinetics of SET‐LRP of methyl acrylate (MA) catalyzed with activated Cu(0) wire in dimethyl sulfoxide (DMSO) at 25 °C demonstrated a dramatic acceleration of the polymerization and the absence of the induction period observed during SET‐LRP catalyzed with nonactivated Cu(0) in several laboratories. Exposure of the activated Cu(0) wire to air results in a lower apparent rate constant of propagation because of gradual oxidation of Cu(0) to Cu2O. This dramatic acceleration of SET‐LRP is similar to that observed with commercial Cu(0) nanopowder except that the polymerization provides excellent molecular weight evolution, very narrow molecular weight distribution and high polymer chain‐end functionality. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010  相似文献   

12.
Non‐transition metal‐catalyzed living radical polymerization (LRP) of vinyl chloride (VC) in water at 25–35 °C is reported. This polymerization is initiated with iodoform and catalyzed by Na2S2O4. In water, S2O dissociates into SO that mediates the initiation and reactivation steps via a single electron transfer (SET) mechanism. The exchange between dormant and active propagating species also includes the degenerative chain transfer to dormant species (DT). In addition, the SO2 released from SO during the SET process can add reversibly to poly(vinyl chloride) (PVC) radicals and provide additional transient dormant ~SO radicals. This novel LRP proceeds mostly by a combination of competitive SET and DT mechanisms and, therefore, it is called SET‐DTLRP. Telechelic PVC with a number‐average molecular weight (Mn) = 2,000–55,000, containing two active ~CH2? CHClI chain ends and a higher syndiotacticity than the commercial PVC were obtained by SET‐DTLRP. This PVC is free of structural defects and exhibits a higher thermal stability than commercial PVC. SET‐DTLRP of VC is carried out under reaction conditions related to those used for its commercial free‐radical polymerization. Consequently, SET‐DTLRP is of technological interest both as an alternative commercial method for the production of PVC with superior properties as well as for the synthesis of new PVC‐based architectures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6267–6282, 2004  相似文献   

13.
The first example of living radical polymerization of vinyl chloride carried out in water at 25 °C is reported. This polymerization was initiated by iodoform and catalyzed by nascent Cu0 produced by the disproportionation of CuI in the presence of strongly CuII binding ligands such as tris(2‐aminoethyl)amine or polyethyleneimine. The resulting poly(vinyl chloride) was free of structural defects, had controlled molecular weight and narrow molecular weight distribution, contained two ~CHClI active chain ends, and had a higher syndiotacticity (62%) than the one obtained by conventional free‐radical polymerization at the same temperature (56%). This novel polymerization proceeds, most probably, by a combination of competitive pathways that involves activation by single electron transfer mediated by nascent Cu0 and degenerative chain transfer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3283–3299, 2003  相似文献   

14.
α,ω‐di(iodo) poly(isobornyl acrylate) macroiniators (α,ω‐di(iodo)PIA) with number average molecular weight from M n,TriSEC = 11,456 to M n,TriSEC = 94,361 were synthesized by single electron transfer‐degenerative chain transfer mediated living radical polymerization (SET‐DTLRP) of isobornyl acrylate (IA) initiated with iodoform (CHI3) and catalyzed by sodium dithionite (Na2S2O4) in water at 35 °C. The plots of number average molecular weight vs conversion and ln{[M]0/[M]} vs time are linear, indicating a controlled polymerization. α,ω‐di(iodo) poly(isobornyl acrylate) have been used as a macroinitiator for the SET‐DTLRP of vinyl chloride (VCM) leading to high Tg block copolymers PVC‐b‐PIA‐b‐PVC. The dynamic mechanical thermal analysis of the block copolymers suggests just one phase indicating that copolymer behaves as a single material. This technology provides the possibility of synthesizing materials based on PVC with higher Tg in aqueous medium. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009  相似文献   

15.
The single‐electron transfer living radical polymerization (SET‐LRP) of water‐soluble monomers, N,N‐dimethylacrylamide (DMA) and N‐isopropylacrylamide (NIPAM), initiated with 2‐methylchloropropionate (MCP) in dipolar aprotic and protic solvents is reported. The radical polymerization of acrylamides is characterized by higher rate constants of propagation and bimolecular termination than acrylates. Therefore, the addition of CuCl2 is required to mediate deactivation in the early stages of the reaction. Through the use of Cu(0)‐wire/Me6‐TREN catalysis, conditions were optimized to minimize the amount of externally added CuCl2 required to maintain a linear evolution of molecular weight and narrow molecular weight distribution. By using less CuCl2 additive, the amount of soluble copper species that must ultimately be removed from the reaction mixture is reduced. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1752–1763, 2010  相似文献   

16.
Cu(0)‐wire/Me6‐TREN is a well established catalyst for living radical polymerization via SET–LRP. Here, it is demonstrated that this polymerization is not just living, but it is in fact the first example of immortal living radical polymerization. The immortality of SET–LRP mediated with Cu(0) wire was demonstrated by attempting, in an unsuccessful way, to irreversible interrupt multiple times the polymerization via exposure to O2 from air. SET–LRP indeed stopped each time when the reaction mixture was exposed to air. However, the SET–LRP reaction, was restarted each time after resealing the reaction vessel and reestablishing the catalytic cycle with the same Cu(0) wire, to produce the same conversion as in the conventional uninterrupted SET–LRP process. Despite the interruption by O2, the reactivated SET–LRP had a good control of molecular weight, molecular weight evolution, and molecular weight distribution, with perfect retention of chain‐end fidelity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2716–2721, 2010  相似文献   

17.
To accelerate the living radical polymerization (LRP) of vinyl chloride (VC) in water the phase transfer catalyzed single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of VC mediated by sodium dithionite (Na2S2O4) was investigated. The fastest polymerization reaction that still produces thermally stable poly(vinyl chloride) (PVC) takes place at 43 °C with the ratio [PTC]0/[Na2S2O4]0 = 0.0075/1. Cetyltrimethylammonium bromide (nC16H33(CH3)3N+Br?, CetMe3NBr) was the phase‐transfer catalyst (PTC) of choice. Under these conditions the first, fast stage of SET–DTLRP of VC was accomplished within 7–8 h when the initial ratio monomer/initiator [VC]0/[CHI3]0 was 800. The number‐average molecular weight (Mn) of the resulting PVC was in good agreement with the theoretical molecular weight (Mth). When the [VC]0/[CHI3]0 ratio was 4800, the fast step of the reaction was accomplished within 17 h, to produce 72% monomer conversion. A deviation of the Mn from the Mth was observed in this case. Possible mechanistic explanations for this deviation as well as for the phase transfer catalyzed SET–DTLRP of VC were suggested. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 779–788, 2005  相似文献   

18.
Cu(0) was prepared via disproportionation of Cu(I)Br in the presence of Me6‐TREN in various solvents in a glove box. The resulting nanopowders were used as mimics of “nascent” Cu(0) catalyst in the single‐electron transfer living radical polymerization (SET‐LRP) of methyl acrylate (MA), providing faster polymerization than any commercial Cu(0) powder, Cu(0) wire, or Cu(I)Br and achieving 80% conversion in only 5 min reaction time. Despite the high rate, a living polymerization was observed with linear evolution of molecular weight, narrow polydispersity, no induction period, and high retention of chain‐end functionality. In addition to providing an unprecedentedly fast, yet controlled LRP of MA, these studies suggest that the very small “nascent” Cu(0) species formed via disproportionation in SET‐LRP are the most active catalysts. Thus, when bulk Cu(0) powder or wire may be the most abundant catalyst and dictates the overall kinetics, any Cu(0) produced via disproportionation will be rapidly consumed and contributes to the overall catalytic cycle. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 403–409, 2010  相似文献   

19.
Single‐electron transfer living radical polymerization (SET‐LRP) proceeds by an outer‐sphere single‐electron transfer mechanism that induces a heterolytic bond cleavage of the initiating and propagating R‐X (where X = Cl, Br, and I) species. Therefore, unlike the homolytic bond cleavage mechanism claimed for ATRP, SET‐LRP is expected to show a small dependence of the nature of the halide group on the apparent rate constant of activation. This means the R‐X with X = Cl, Br, and I must all be efficient initiators for SET‐LRP and no chain transfer must be observed in the case of initiators with X = Br and I. Here, we report the SET‐LRP of methyl acrylate initiated with the alkyl chlorides methyl‐2‐chloropropionate (MCP) and chloroform (CHCl3) and catalyzed by Cu(0)/Me6‐TREN/CuCl2 in DMSO at 25 °C. A combination of kinetic and structural analysis was used to elucidate the MCP and CHCl3 initiating behavior under SET‐LRP conditions, and to demonstrate the very small dependence of the SET‐LRP apparent rate constant of propagation on X while providing polymers with well defined architecture. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4917–4926, 2008  相似文献   

20.
Single electron transfer‐living radical polymerization (SET‐LRP) represents a robust and versatile method for the rapid synthesis of macromolecules with defined architecture. The synthesis of poly(methyl methacrylate) via SET‐LRP in dimethyl sulfoxide (DMSO) by using CCl4 as initiator is demonstrated in this work. Resorting to a rather simple Cu(0)/Me6‐TREN catalyst a method was established that allowed for the straightforward design of well‐defined poly(methyl methacrylate). The reactions were performed at various temperatures (25, 50, 60, and 80 °C) and complete monomer conversion could be achieved. The polymerizations obeyed first order kinetic, the molecular weights increased linearly with conversion and the polymers exhibited narrow molecular weight distributions all indicating the livingness of the process. By providing a small amount of hydrazine to the reaction mixture the polymerization could be conducted in presence of air omitting the need for any elaborated deoxygenation procedures. This methodology offers an elegant way to synthesize functionalized poly(methyl methacrylate) with perfect control over the polymerization process as well as molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2243–2250, 2010  相似文献   

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