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1.
We describe the synthesis of diblock and triblock copolymers by sequential atom transfer radical polymerization of styrene and acetoxymethylstyrene. Contrary to the usual block copolymerization involving isolation of the macroinitiator, a convenient one‐pot procedure is developed. This is possible because of the preferential polymerization of acetoxymethylstyrene, even in the presence of residual styrene, as inferred from characterization of the intermediate polystyrenes and the block copolymers by size exclusion chromatography, 1H NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry, and GPEC techniques. The latent acetoxy functionalities in these block copolymers are shown to be easily unmasked to ? OH and ? Br functionalities, with the potential for block ionomers and dense graft architectures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 575–583, 2005  相似文献   

2.
Two sets of styrene‐based semifluorinated block copolymers, one with a perfluoroether pendant group and another with a perfluoroalkyl group, were synthesized by atom transfer radical polymerization. Microphase separation of the block copolymers was established by small‐angle X‐ray scattering and differential scanning calorimetry (DSC). DSC measurements also showed that the perfluoroether‐based polymer had a low glass‐transition temperature (?44 °C). Contact‐angle measurements indicated that the semifluorinated block copolymers had low surface energies (ca. 13 mJ/m2). These materials hold promise as low‐surface‐energy additives or surfactants for supercritical CO2 applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 853–861, 2004  相似文献   

3.
The effects of Br connected groups on atom transfer nitroxide radical coupling (ATNRC) reaction were investigated. Two precursors methoxyl poly(ethylene oxide)‐b‐poly(ethylene oxide‐co‐2‐bromoiso butyryloxy glycidyl ether) (mPEO‐b‐Poly(EO‐co‐BiBGE)) and methoxyl poly(ethylene oxide)‐b‐poly(2‐bromoiso butyryloxy glycidyl ether) (mPEO‐b‐Poly(BiBGE)) with different ? C(CH3)2Br density were designed and synthesized firstly, and then ATNRC reaction were completed between these precursors and 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy poly(ε‐caprolactone) (TEMPO‐PCL) in the presence or absence of St monomers, respectively. The results showed that the structure of Br connected groups showed an important effect on ATNRC reaction, and the ATNRC reaction with high efficiency could be realized by transforming the higher active Br connected groups into the lower one by the addition of small amount of St monomers. The final comb‐like block copolymers mPEO‐b‐[Poly(EO‐co‐Gly)‐g‐(St1.8b‐PCL)] and mPEO‐b‐[Poly(Gly)‐g‐(St2.4b‐PCL)] with high coupling efficiency were obtained by this strategy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1633–1640, 2010  相似文献   

4.
A stable nitroxyl radical functionalized with an initiating group for atom transfer radical polymerization (ATRP), 4‐(2‐bromo‐2‐methylpropionyloxy)‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (Br‐TEMPO), was synthesized by the reaction of 4‐hydroxyl‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy with 2‐bromo‐2‐methylpropionyl bromide. Stable free radical polymerization of styrene was then carried out using a conventional thermal initiator, dibenzoyl peroxide, along with Br‐TEMPO. The obtained polystyrene had an active bromine atom for ATRP at the ω‐end of the chain and was used as the macroinitiator for ATRP of methyl acrylate and ethyl acrylate to prepare block copolymers. The molecular weights of the resulting block copolymers at different monomer conversions shifted to higher molecular weights and increased with monomer conversion. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2468–2475, 2006  相似文献   

5.
Copper(I)‐mediated living radical polymerization was used to synthesize amphiphilic block copolymers of poly(n‐butyl methacrylate) [P(n‐BMA)] and poly[(2‐dimethylamino)ethyl methacrylate] (PDMAEMA). Functionalized bromo P(n‐BMA) macroinitiators were prepared from monofunctional, difunctional, and trifunctional initiators: 2‐bromo‐2‐methylpropionic acid 4‐methoxyphenyl ester, 1,4‐(2′‐bromo‐2′‐methyl‐propionate)benzene, and 1,3,5‐(2′‐bromo‐2′‐methylpropionato)benzene. The living nature of the polymerizations involved was investigated in each case, leading to narrow‐polydispersity polymers for which the number‐average molecular weight increased fairly linearly with time with good first‐order kinetics in the monomer. These macroinitiators were subsequently used for the polymerization of (2‐dimethylamino)ethyl methacrylate to obtain well‐defined [P(n‐BMA)xb‐PDMAEMAy]z diblock (15,900; polydispersity index = 1.60), triblock (23,200; polydispersity index = 1.24), and star block copolymers (50,700; polydispersity index = 1.46). Amphiphilic block copolymers contained between 60 and 80 mol % hydrophilic PDMAEMA blocks to solubilize them in water. The polymers were quaternized with methyl iodide to render them even more hydrophilic. The aggregation behavior of these copolymers was investigated with fluorescence spectroscopy and dynamic light scattering. For blocks of similar comonomer compositions, the apparent critical aggregation concentration (cac = 3.22–7.13 × 10?3 g L?1) and the aggregate size (ca. 65 nm) were both dependent on the copolymer architecture. However, for the same copolymer structure, increasing the hydrophilic PDMAEMA block length had little effect on the cac but resulted in a change in the aggregate size. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 439–450, 2002; DOI 10.1002/pola.10122  相似文献   

6.
The controlled free‐radical polymerization of styrene and chloromethylstyrene monomers in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl (TEMPO) has been studied with the aim of synthesizing block copolymers with well‐defined structures. First, TEMPO‐capped poly(chloromethylstyrene) was prepared. Among several initiating systems [self‐initiation, dicumyl peroxide, and 2,2′‐azobis(isobutyronitrile)], the last offered the best compromise for obtaining a good control of the polymerization and a fast polymerization rate. The rate of the TEMPO‐mediated polymerization of chloromethylstyrene was independent of the initial concentration of TEMPO but unexpectedly higher than the rate of the thermal self‐initiated polymerization of chloromethylstyrene. Transfer reactions to the chloromethyl groups were thought to play an important role in the polymerization kinetics and the polydispersity index of the resulting poly(chloromethylstyrene). Second, this first block was used as a macroinitiator in the polymerization of styrene to obtain the desired poly(chloromethylstyrene‐b‐styrene) block copolymer. The kinetic modeling of the block copolymerization was in good agreement with experimental data. The block copolymers obtained in this work exhibited a low polydispersity index (weight‐average molecular weight/number‐average molecular weight < 1.5) and could be chemically modified with nucleophilic substitution reactions on the benzylic site, opening the way to a great variety of architectures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3845–3854, 2000  相似文献   

7.
Well‐defined sulfonated polystyrene and block copolymers with n‐butyl acrylate (nBA) were synthesized by CuBr catalyzed living radical polymerization. Neopentyl p‐styrene sulfonate (NSS) was polymerized with ethyl‐2‐bromopropionate initiator and CuBr catalyst with N,N,N′,N′‐pentamethylethyleneamine to give poly(NSS) (PNSS) with a narrow molecular weight distribution (MWD < 1.12). PNSS was then acidified by thermolysis resulting in a polystyrene backbone with 100% sulfonic acid groups. Random copolymers of NSS and styrene with various composition ratios were also synthesized by copolymerization of NSS and styrene with different feed ratios (MWD < 1.11). Well defined block copolymers with nBA were synthesized by sequential polymerization of NSS from a poly(n‐butyl acrylate) (PnBA) precursor using CuBr catalyzed living radical polymerization (MWD < 1.29). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5991–5998, 2008  相似文献   

8.
The synthesis of poly(methyl acrylate)-block-poly(gamma-benzyl-L-glutamate) (PMA-b-PBLG) diblock copolymers, using atom-transfer radical polymerization (ATRP) of methyl acrylate and living polymerization of gamma-benzyl-L-glutamate-N-carboxyanhydride (Glu-NCA) is described. Amido-amidate nickelacycle end groups were incorporated onto amino-terminated poly(methyl acrylates), and the resulting complexes were successfully used as macroinitiators for the growth of polypeptide segments. This method allows the controlled preparation of polypeptide-block-poly(methyl acrylate) diblock architectures with control over polypeptide chain length and without the formation of homopolypeptide contaminants.  相似文献   

9.
We report the polymerization of rhenium‐containing methacrylates by atom transfer radical polymerization. The structure of the monomer was confirmed by X‐ray crystallography, which showed the bulkiness of the metal‐complex moiety. The rhenium complexes were polymerized in the presence of copper(I) bromide, 1,1,4,7,7‐pentamethyldiethylenetriamine, and methyl 2‐bromopropionate. They were copolymerized with methyl methacrylate in different monomer ratios. An ABA triblock copolymer was also synthesized with poly(methyl methacrylate) as the macroinitiator. When 2,2′‐bipyridine was used as the ligand for the copper catalyst in the polymerizations, it underwent a ligand exchange process with the iminopyridine ligand in the monomer. The neutral rhenium complex in the homopolymers and copolymers could be converted into ionic forms by the replacement of the chloride with an imidazole ligand, and the solubility of the resulting ionic polymers was greatly enhanced. The photosensitizing properties of the doped and undoped polymer films were investigated by the measurement of the photocurrent response under an externally applied electric field. The photoconductivities of the polymers were approximately 10?12–10?13 Ω?1 cm?1. The experimental quantum efficiencies were simulated with Onsager's theory, and they showed that the initial quantum yield and thermalization distance were 10?3 and 1.7 nm, respectively. Transmission electron microscopy showed that the rhenium complexes aggregated to form domains with dimensions of approximately 20–30 nm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1292–1308, 2005  相似文献   

10.
The atom transfer radical polymerization of methyl methacrylate (MMA) and n‐butyl methacrylate (n‐BMA) was initiated by a poly(ethylene oxide) chloro telechelic macroinitiator synthesized by esterification of poly(ethylene oxide) (PEO) with 2‐chloro propionyl chloride. The polymerization, carried out in bulk at 90 °C and catalyzed by iron(II) chloride tetrahydrate in the presence of triphenylphosphine ligand (FeCl2 · 4H2O/PPh3), led to A–B–A amphiphilic triblock copolymers with MMA or n‐BMA as the A block and PEO as the B block. A kinetic study showed that the polymerization was first‐order with respect to the monomer concentration. Moreover, the experimental molecular weights of the block copolymers increased linearly with the monomer conversion, and the molecular weight distribution was acceptably narrow at the end of the reaction. These block copolymers turned out to be water‐soluble through the adjustment of the content of PEO blocks (PEO content >90% by mass). When the PEO content was small [monomer/macroinitiator molar ratio (M/I) = 300], the block copolymers were water‐insoluble and showed only one glass‐transition temperature. With an increase in the concentration of PEO (M/I = 100 or 50) in the copolymer, two glass transitions were detected, indicating phase separation. The macroinitiator and the corresponding triblock copolymers were characterized with Fourier transform infrared, proton nuclear magnetic resonance, size exclusion chromatography analysis, dynamic mechanical analysis, and differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5049–5061, 2005  相似文献   

11.
This paper describes a new method to prepare graft copolymers, such as polyethylene‐g‐polystyrene (PE‐g‐PS), with a relatively well‐controlled reaction mechanism. The chemistry involves a transformation process from the metallocene copolymerization of ethylene and m,p‐methylstyrene (m,p‐MS) to nitroxide‐mediated “living” free radical polymerization (LRFP) of styrene. The metallocene catalysis produces ethylene‐co‐m,p‐methylstyrene (EMS) random copolymers. Next, 1‐hydroxyl‐2,2,6,6‐tetramethylpiperidine (HO‐TEMPO) was synthesized by the reduction of TEMPO with sodium ascorbate. The macroinitiator (EMS‐TEMPO) was synthesized with the bromination reaction of EMS, and the following nucleofilic reaction with this functional nitroxyl compound. The resulting macroinitiator (EMS‐TEMPO) for LRFP was then heated in the presence of styrene to form graft copolymer. DSC, 1H‐NMR, FTIR spectroscopy were employed to investigate the structure of the polymers. The results of Molau test showed that PE‐g‐PS could be a potential good compatilizer. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

12.
Novel and well‐defined dendrimer‐star, block‐comb polymers were successfully achieved by the combination of living ring‐opening polymerization and atom transfer radical polymerization on the basis of a dendrimer polyester. Star‐shaped dendrimer poly(?‐caprolactone)s were synthesized by the bulk polymerization of ?‐caprolactone with a dendrimer initiator and tin 2‐ethylhexanoate as a catalyst. The molecular weights of the dendrimer poly(?‐caprolactone)s increased linearly with an increase in the monomer. The dendrimer poly(?‐caprolactone)s were converted into macroinitiators via esterification with 2‐bromopropionyl bromide. The star‐block copolymer dendrimer poly(?‐caprolactone)‐block‐poly(2‐hydroxyethyl methacrylate) was obtained by the atom transfer radical polymerization of 2‐hydroxyethyl methacrylate. The molecular weights of these copolymers were adjusted by the variation of the monomer conversion. Then, dendrimer‐star, block‐comb copolymers were prepared with poly(L ‐lactide) blocks grafted from poly(2‐hydroxyethyl methacrylate) blocks by the ring‐opening polymerization of L ‐lactide. The unique and well‐defined structure of these copolymers presented thermal properties that were different from those of linear poly(?‐caprolactone). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6575–6586, 2006  相似文献   

13.
The synthesis of block copolymers consisting of a polyethylene segment and either a poly(meth)acrylate or polystyrene segment was accomplished through the combination of postmetallocene-mediated ethylene polymerization and subsequent atom transfer radical polymerization. A vinyl-terminated polyethylene (number-average molecular weight = 1800, weight-average molecular weight/number-average molecular weight =1.70) was synthesized by the polymerization of ethylene with a phenoxyimine zirconium complex as a catalyst activated with methylalumoxane (MAO). This polyethylene was efficiently converted into an atom transfer radical polymerization macroinitiator by the addition of α-bromoisobutyric acid to the vinyl chain end, and the polyethylene macroinitiator was used for the atom transfer radical polymerization of n-butyl acrylate, methyl methacrylate, or styrene; this resulted in defined polyethylene-b-poly(n-butyl acrylate), polyethylene-b-poly(methyl methacrylate), and polyethylene-b-polystyrene block copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 496–504, 2004  相似文献   

14.
This study reports an application of trichloroethanol (TCE) as a bifunctional initiator for the synthesis of block copolymers (BCPs) by organocatalyzed ring‐opening polymerization (OROP) and atom transfer radical polymerization (ATRP). TCE was employed to synthesize a low dispersity poly (valerolactone) macroinitiator, which was subsequently used for the ATRP of tert‐butyl methacrylate. While it is known that TCE can serve as an initiator in ATRP, the ability to induce polymerization under OROP is reported for the first time. The formation of well‐defined BCPs was confirmed by gel permeation chromatography and 1H NMR. Computational studies were performed to obtain a molecular‐level understanding of the ring‐opening polymerization mechanism involving TCE as initiator. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 563–569  相似文献   

15.
ABCBA‐type pentablock copolymers of methyl methacrylate (MMA), styrene (S), and isobutylene (IB) were prepared by a three‐step synthesis, which included atom transfer radical polymerization (ATRP) and cationic polymerization: (1) poly(methyl methacrylate) (PMMA) with terminal chlorine atoms was prepared by ATRP initiated with an aromatic difunctional initiator bearing two trichloromethyl groups under CuCl/2,2′‐bipyridine catalysis; (2) PMMA with the same catalyst was used for ATRP of styrene, which produced a poly(S‐b‐MMA‐b‐S) triblock copolymer; and (3) IB was polymerized cationically in the presence of the aforementioned triblock copolymer and BCl3, and this produced a poly(IB‐b‐S‐b‐MMA‐b‐S‐b‐IB) pentablock copolymer. The reaction temperature, varied from ?78 to ?25 °C, significantly affected the IB content in the product; the highest was obtained at ?25 °C. The formation of a pentablock copolymer with a narrow molecular weight distribution provided direct evidence of the presence of active chlorine at the ends of the poly(S‐b‐MMA‐b‐S) triblock copolymer, capable of the initiation of the cationic polymerization of IB in the presence of BCl3. A differential scanning calorimetry trace of the pentablock copolymer (20.1 mol % IB) showed the glass‐transition temperatures of three segregated domains, that is, polyisobutylene (?87.4 °C), polystyrene (95.6 °C), and PMMA (103.7 °C) blocks. One glass‐transition temperature (104.5 °C) was observed for the aforementioned triblock copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6098–6108, 2004  相似文献   

16.
A new method to prepare the polypropylene (PP) macroinitiator for controlled radical polymerization was described. Bromination of terminally-unsaturated PP was carried out by using N-bromosuccinimide and 2,2′-azobis(isobutyronitrile) to give a brominated PP (PP-Br), that has allylic bromide moieties at or near the chain ends. Thus, the obtained PP-Br was successfully used as a macroinitiator for radical polymerization of styrene, methyl methacrylate, and n-butyl acrylate using a copper catalyst system. From 1H NMR analysis, it was confirmed that the chain extension polymerization was certainly initiated from allylic bromide moieties with high efficiency, leading to the PP-based block copolymers linking the polar segment. From differential scanning calorimetry, it was observed that peak melting temperature of block copolymers was higher than that of PP-Br and the obtained PP-PS block copolymers with different compositions of each segment demonstrated the unique morphological features due to the microphase separation between both segments. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 812–823, 2009  相似文献   

17.
An asymmetric difunctional initiator 2‐phenyl‐2‐[(2,2,6,6 tetramethylpiperidino)oxy] ethyl 2‐bromo propanoate ( 1 ) was used for the synthesis of ABC‐type methyl methacrylate (MMA)‐tert‐butylacrylate (tBA)‐styrene (St) triblock copolymers via a combination of atom transfer radical polymerization (ATRP) and stable free‐radical polymerization (SFRP). The ATRP‐ATRP‐SFRP or SFRP‐ATRP‐ATRP route led to ABC‐type triblock copolymers with controlled molecular weight and moderate polydispersity (Mw/Mn < 1.35). The block copolymers were characterized by gel permeation chromatography and 1H NMR. The retaining chain‐end functionality and the applying halide exchange afforded high blocking efficiency as well as maintained control over entire routes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2025–2032, 2002  相似文献   

18.
Atom transfer radical polymerization (ATRP) and ring‐opening polymerization (ROP) were combined to synthesize poly(?‐caprolactone‐co‐octadecyl methacrylate‐co‐dimethylaminoethyl methacrylate) copolymers possessing a triblock or random block structure. Various synthetic pathways (sequential or simultaneous approaches) were investigated for the synthesis of both copolymers. For the preparation of these copolymers, an initiator with dual functionality for ATRP/anionic ring‐opening polymerization, 2‐hydroxyethyl 2‐bromoisobutyrate, was used. Copolymers were prepared with good structural control and low polydispersities (weight‐average molecular weight/number‐average molecular weight < 1.2), but one limitation was identified: the dimethylaminoethyl methacrylate (DMAEMA) block had to be synthesized after the ?‐caprolactone block. ROP could not proceed in the presence of DMAEMA because the complexation of the amine groups in poly(dimethylaminoethyl methacrylate) deactivated tin(II) hexanoate, which was used as a catalyst for ROP. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1498–1510, 2005  相似文献   

19.
A stable nitroxyl radical functionalized with two initiating groups for atom transfer radical polymerization (ATRP), 4-(2,2-bis-(methyl 2-bromo isobutyrate)-propionyloxy)-2,2,6,6-tetramethyl-1-piperidinyloxy (Br2-TEMPO), was synthesized by reacting 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy with 2,2-bis-(methyl 2-bromo isobutyrate) propanoic acid. Stable free radical polymerization of styrene was then carried out using a conventional thermal initiator, dibenzoyl peroxide, along with Br2-TEMPO. The obtained polystyrene had two active bromine atoms for ATRP at the ω-end of the chain and was further used as the macroinitiator for ATRP of methyl acrylate and ethyl acrylate to prepare AB2-type miktoarm star-shaped copolymers. The molecular weights of the resulting miktoarm star-shaped copolymers at different monomer conversions shifted to higher molecular weights without any trace of the macroinitiator, and increased with monomer conversion.  相似文献   

20.
Poly(dimethylsiloxane)‐containing diblock and triblock copolymers were prepared by the combination of anionic ring‐opening polymerization (AROP) of hexamethylcyclotrisiloxane (D3) and nitroxide‐mediated radical polymerization (NMRP) of methyl acrylate (MA), isoprene (IP), and styrene (St). The first step was the preparation of a TIPNO‐based alkoxyamine carrying a 4‐bromophenyl group. The alkoxyamine was then treated with Li powder in ether, and AROP of D3 was carried out using the resulting lithiophenyl alkoxyamine at room temperature, giving functional poly(D3) with Mw/Mn of 1.09–1.16. NMRPs of MA, St, and IP from the poly(D3) at 120 °C gave poly(D3b‐MA), poly(D3b‐St), and poly(D3b‐IP) diblock copolymers, and subsequent NMRPs of St from poly(D3b‐MA) and poly(D3b‐IP) at 120 °C gave poly(D3b‐MA‐b‐St) and poly(D3b‐IP‐b‐St) triblock copolymers. The poly(dimethylsiloxane)‐containing diblock and triblock copolymers were analyzed by 1H NMR and size exclusion chromatography. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6153–6165, 2005  相似文献   

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