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Journal ArticleDOI

Synthesis and Characterization of Block Copolymers of P(MMA‐b‐n‐BA‐b‐MMA) via Ambient Temperature ATRP of MMA

13 Apr 2005-Journal of Macromolecular Science, Part A (Taylor & Francis Group)-Vol. 42, Iss: 4, pp 471-484

Abstract: A binol ester initiator was used as a bifunctional ATRP initiator in combination with PMDETA/copper bromide catalyst system in DMF to synthesize n‐butyl acrylate macroinitiator at 50°C. The resulting macroinitiator was used for a detailed investigation of the ATRP of methyl methacrylate (MMA) with CuCl/N,N,N′,N′,N″‐pentamethyldiethy‐lenetriamine (PMDETA) catalyst system in anisole at 30°C. Thus, the MMA polymerization is shown to proceed with first order kinetics, with predicted molecular weight and narrow polydispersity indices. Gel permeation chromatography (GPC) and NMR were used for the characterization of the polymers synthesized.
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22 Feb 2011-
Abstract: Catalyst components for the(co)polymerization of ethylene comprising Ti, Mg, halogen, ORI groups, where RI is a C1-C12 hydrocarbon group optionally containing heteroatoms, having ORI/Ti molar ratio in the range 0.1-1.5, a Mg/Ti molar ratio of less than 8, an amount of titanium, with respect to the total weight of said solid catalyst component, higher than 4% by weight characterized by a specific SS-NMR pattern are particularly useful for preparing narrow MWD crystalline ethylene polymers.

201 citations

Journal ArticleDOI
Dhruba J. Haloi1, Souvik Ata1, Nikhil K. Singha1, Dieter Jehnichen2  +2 moreInstitutions (3)
TL;DR: Small-angle X-ray scattering (SAXS) analysis of AB and ABA block copolymers showed scattering behavior inside the measuring limits indicating nanophase separation, however, SAXS pattern of AB diblockCopolymers indicated general phase separation only, whereas for ABA triblock copolymer an ordered or mixed morphology could be deduced, which is assumed to be the reason for the better mechanical properties achieved with ABABlocks.
Abstract: Acrylic block copolymers have several advantages over conventional styrenic block copolymers, because of the presence of a saturated backbone and polar pendant groups. This investigation reports the preparation and characterization of di- and triblock copolymers (AB and ABA types) of 2-ethylhexyl acrylate (EHA) and methyl methacrylate (MMA) via atom transfer radical polymerization (ATRP). A series of block copolymers, PEHA-block-PMMA(AB diblock) and PMMA-block-PEHA-block-PMMA(ABA triblock) were prepared via ATRP at 90 °C using CuBr as catalyst in combination with N,N,N′,N″,N″-pentamethyl diethylenetriamine (PMDETA) as ligand and acetone as additive. The chemical structure of the macroinitiators and molar composition of block copolymers were characterized by 1H NMR analysis, and molecular weights of the polymers were analyzed by GPC analysis. DSC analysis showed two glass transition temperatures (Tg), indicating formation of two domains, which was corroborated by AFM analysis. Small-angle X-ray scattering ...

34 citations

Journal ArticleDOI
Abstract: Well defined graft copolymers are prepared by "grafting from" atom transfer radical polymerization (ATRP) at room temperature (30 °C). The experiments were aimed at grafting methacrylates and styrene at latent initiating sites of polystyrene. For this purpose, the benzylic hydrogen in polystyrene was subjected to allylic bromination with N-bromosuccinimide and azobisisobutrylnitirle to generate tertiary bromide ATRP initiating sites (Br-C-PS). The use of Br-C-PS with lesser mol % of bromide initiating groups results in better control and successful graft copolymerization. This was used to synthesize a series of new graft copolymers such as PS-g-PBnMA, PS-g-PBMA, PS-g-GMA, and PS-g-(PMMA-b-PtBA) catalyzed by CuBr/ PMDETA system, in bulk, at room temperature. The polymers are characterized by GPC, NMR, FTIR, TEM, and TGA. Graft copolymerization followed by block polymerization enabled the synthesis of highly branched polymer brush, in which the grafting density can be adjusted by appropriate choice of bromide concentration in the polystyrene.

30 citations

Journal ArticleDOI
Abstract: Tetrahydrofurfuryl methacrylate (THFMA), a heterocyclic monomer was polymerized by ambient temperature Atom Transfer Radical Polymerization (AT ATRP) using CuX/PMDETA/EBiB system. THFMA was found to undergo very rapid polymerization, in bulk. For a target DP > 200, bulk polymerization results in cross-linking as evidenced by (CH2)n,wag peaks (IR spectroscopy). Atom Transfer Radical copolymerization (ATRcP) of THFMA with MMA was performed and the reactivity ratios were calculated from the copolymer composition, as determined by 1H NMR, using Fineman–Ross and Kelen–Tudos methods. The reactivity ratios determined for ATRP were found to be significantly different from the literature values for conventional free radical polymerization (CFRP). This may be due to the coordination of copper catalytic system with the oxygen atom of the tetrahydrofurfuryl group that could lead to the variation in reactivity ratios. 1H NMR evidence for catalyst–monomer interaction is also provided.

22 citations

Journal ArticleDOI
Kai Pan1, Long Jiang1, Juan Zhang1, Yi Dan1Institutions (1)
Abstract: A series of copper-based reverse atom transfer radical polymerizations (ATRP) were carried out for methyl methacrylate (MMA) at same conditions (in xylene, at 80°C) using N,N,N′,N′-teramethylethylendiamine (TMEDA), N,N,N′,N′,N′-pentamethyldiethylentriamine (PMDETA), 2-2′-bipyridine, and 4,4′-Di(5-nonyl)-2,2′-bipyridine as ligand, respectively. 2,2′-azobis(isobutyronitrile) (AIBN) was used as initiator. In CuBr2/bpy system, the polymerization is uncontrolled, because of the poor solubility of CuBr2/bpy complex in organic phase. But in other three systems, the polymerizations represent controlled. Especially in CuBr2/dNbpy system, the number-average molecular weight increases linearly with monomer conversion from 4280 up to 14,700. During the whole polymerization, the polydispersities are quite low (in the range 1.07–1.10). The different results obtained from the four systems are due to the differences of ligands. From the point of molecular structure of ligands, it is very important to analyze deeply the two relations between (1) ligand and complex and (2) complex and polymerization. The different results obtained were discussed based on the steric effect and valence bond theory. The results can help us deep to understand the mechanism of ATRP. The presence of the bromine atoms as end groups of the poly(methyl methacrylate) (PMMA) obtained was determined by 1H-NMR spectroscopy. PMMA obtained could be used as macroinitiator to process chain-extension reaction or block copolymerization reaction via a conventional ATRP process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

12 citations

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Journal ArticleDOI
Abstract: Atom transfer radical polymerization (ATRP) is one of the most successful methods to polymerize styrenes, (meth)acrylates and a variety of other monomers in a controlled fashion, yielding polymers with molecular weights predetermined by the ratio of the concentrations of consumed monomer to introduced initiator and with low polydispersities. Because of its radical nature, ATRP is tolerant to many functionalities in monomers leading to polymers with functionalities along the chains. Moreover, the initiator used determines the end groups of the polymers. By using a functional initiator, functionalities such as vinyl, hydroxyl, epoxide, cyano and other groups have been incorporated at one chain end, while the other chain end remains an alkyl halide. The polymer can be dehalogenated in a one-pot process or the halogen end groups can be transformed to other functionalities using nucleophilic substitution reactions or electrophilic addition reactions. Moreover, utilizing the ability of the halogen chain end to be reactivated, radical addition reactions can be used to incorporate allyl end groups, insert one less reactive monomer unit at the chain end, or to end-cap the polymer chain. With ATRP, functionality and architecture can be combined resulting in multifunctional polymers of different compositions and shapes such as block copolymers, multiarmed stars or hyperbranched polymers.

1,148 citations

Journal ArticleDOI
Marc Husseman1, Eva Malmström1, Molly McNamara1, Mathew Mate1  +7 moreInstitutions (1)
04 Feb 1999-Macromolecules
Abstract: The preparation of a wide variety of unique polymer brush structures can be accomplished by “living” free radical polymerization of vinyl monomers from surface-tethered alkoxyamines or from tethered α-halo esters in the presence of (PPh3)2NiBr2. The use of a “living” free radical process permits the molecular weight and polydispersity of the covalently attached polymer chains to be accurately controlled while also allowing the formation of block copolymers by the sequential growth of monomers from the surface. These block and random copolymer brushes have been used to control surface properties.

856 citations

Journal ArticleDOI
01 Aug 1998-Advanced Materials
Abstract: The development of new polymeric materials is based on the availability of methods, principally living polymerizations, that allow well-defined polymers to be prepared. Living polymerizations are chain-growth polymerizations that proceed in the absence of irreversible chain transfer and chain termination. Provided that initiation is complete and exchange between species of various reactivities is fast, one can adjust the final average molecular weight of the polymer by varying the initial monomer-to-initiator ratio (DPn = D[M]/[I]0) while maintaining a narrow molecular weight distribution (1.0 < Mw/Mn < 1.5). [8,9] Also, one has control over the chemistry and structure of the initiator and active end group, so polymers can be end-functionalized and block copolymerized with other monomers. Thus, using only a few monomers and a living polymerization, one can create many new materials with vastly differing properties simply by varying the topology of the polymer (i.e., comb, star, dendritic, etc.), the composition of the polymer (i.e., random, periodic, graft, etc.), or the functional groups at various sites on the polymer (i.e., end, center, side, etc.) (Fig. 1). Examples of such materials prepared by atom transfer radical polymerization (ATRP) are shown later in this review. Much of the academic and industrial research on materials development has focused on coordination, cationic, anionic, and ring-opening polymerizations due to the availability of controlled/living polymerizations of these types. Free-radical polymerizations accounted for approximately half of the total production of polymers in the United States in 1995. Despite its tremendous utility, a significant drawback to free-radical polymerization is the lack of macromolecular structure control due to near diffusion-controlled radical coupling and disproportionation. Therefore, the development of controlled/living radical polymerization methods has been a long-standing goal in polymer chemistry. The last five years have seen the realization of this goal and the rapid growth in the development and understanding of new controlled radical polymerizations. In this discussion, we give a brief overview of recent developments in controlled radical polymerizations and describe in more depth the progress that has been made in the development of ATRP.

852 citations

Journal ArticleDOI
10 Dec 1998-Macromolecules
Abstract: Recent progress in the field of densely grafted, or “brush” (co)polymers has prompted a need to develop efficient methods to synthesize a wider variety of materials with the same basic architectural design. These brushlike macromolecules have been prepared previously using the macromonomer method.1-6 Macromonomers, usually prepared by anionic polymerization, were homopolymerized using conventional radical methods to maximize the number of branches possible from a linear backbone based on vinyl monomers. Upon fractionation of these materials using size exclusion chromatography, samples of narrow polydispersities were obtained which could then be cast on surfaces to form highly ordered thin films. To avoid the rigorous methods necessary for ionic polymerizations and sample fractionation, and to extend the variety of compositional content of these types of materials, atom transfer radical polymerization (ATRP) has been used to prepare similar macromolecular architectures. The approach described here involves grafting from a macroinitiator and can offer greater versatility in terms of both the length and the composition of the backbone and/or the side chains than previous methods which employed the synthesis of high molecular weight macromonomers and their subsequent polymerization by uncontrolled radical techniques; to obtain welldefined polymeric brushes required their fractionation, generally by SEC. To our knowledge, there are no known examples of using a macroinitaitor with a grafting site at each repeat unit to make well-defined polymeric brushes. Combinations of nitroxide-mediated, conventional free radical polymerization and ATRP to prepare graft copolymers from macroinitiators have been used previously.7,8 ATRP has also been combined with conventional radical polymerization to prepare amphiphilic graft copolymers9 and thermoplastic elastomers,10 as well. In each of these cases, however, the materials are loosely grafted, having been prepared from a macroinitiator which is a copolymer containing both initiation/ branch sites and spacing repeat units. Controlled radical polymerization and ATRP in particular afford access to materials of controlled molecular weight, predicted by the ratio of consumed monomer to initiation sites.11,12 This method also yields polymer segments of narrow molecular weight distributions13 in addition to being applicable to a host of vinyl monomers such as styrene, (meth)acrylates, acrylonitrile, etc.14 Thus, there are many possibilities which make its application to the area of brush (co)polymers appealing. Included here are preliminary synthetic data and AFM images which show that it is possible to prepare densely grafted copolymers using ATRP. Two approaches were used to prepare the macroinitiators, Scheme 1. The first involved conventional free radical homopolymerization of 2-(2-bromopropionyloxy)ethyl acrylate (BPEA)15 using AIBN in the presence of carbon tetrabromide to attenuate the molecular weight (Mn ) 27 300, Mw/Mn ) 2.3). By use of AIBN as an intiator to prepare the ATRP macroinitiator, a polymer with a broad molecular weight distribution was obtained. Such a macroinitiator would consequently result in the formation of brush polymers with broad molecular weight distributions, no matter how well controlled the polymerization of the side chains. Thus, the preparation of a well-defined macroinitiator was undertaken. In the second approach, trimethylsilylprotected 2-hydroxyethyl methacrylate (HEMA-TMS)16 was polymerized via ATRP and subsequently esterified with 2-bromoisobutyryl bromide (BriBuBr) in the presence of a catalytic amount of tetrabutylammonium fluoride (TBAF) to yield a different macroinitiator, poly(2-(2-bromoisobutyryloxy)ethyl methacrylate) (pBIEM)16 with controlled molecular weight and low polydispersity (Mn ) 55 500, Mw/Mn ) 1.3), Table 1. It should be noted that the macroinitiator prepared using ATRP was composed of a stiffer methacrylate structure and with a 2-bromoisobutyryl initiation site while the free radically prepared pBPEA contained an acrylate backbone and 2-bromopropionyl initiation sites. However, both types of initiating species have been shown to initiate styrene polymerization well.14 Both polymers were then used as macroinitiators for ATRP of styrene (S) and butyl acrylate (BA). Side chains with a degree of polymerization of about 40 from a macroinitiator of pBIEM with a Mn of approximately 50 000 (which contained about 200 initiation sites per Scheme 1 9413 Macromolecules 1998, 31, 9413-9415

509 citations

Journal ArticleDOI
Krzysztof Matyjaszewski1Institutions (1)
Abstract: Fundamentals of controlled/“living” radical polymerization are given together with a discussion of selected initiating/catalytic systems which provide structural, compositional, and functionality control during radical polymerization. Four systems which enable the synthesis of polymers with low polydispersities (Mw/Mn 10 000), and high degrees of functionality are: nitroxide-mediated polymerization of styrene and styrene copolymers; organometallic compounds used for polymerization of acrylates; atom transfer radical polymerization of various monomers; and the degenerative transfer process. Also important in this field are new structural features and potential applications of controlled radical polymerization.

400 citations