Atom Transfer Polymerization ATRP

ATRP gives excellent control of polymer chain architecture. For industrial use, however, two problems need to be overcome residual halides and metals in the product would be a problem for electronic device uses. The rate of polymerization may be too slow. This is because the chain end concentrations must be low so that typical radical chain termination is kept to a minimum. Chain termination is a second order reaction and will be minimized by low concentrations of chain end radicals. The low rate of polymerization may increase the cost of the process since the optimum time for a polymerization run is about 6 h. 

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Variations on this process include atom transfer polymerization (ATRP), "" which includes metal catalyzed atom transfer, to give the propagating radical as illustrated in Scheme 3 for Cu(I) catalyzed polymerization of styrene using 1-arylethyl chlorides. 

The ruthenium catalyst RuCl2(= CHPh)(PCy3)2 is able to promote both alkene metathesis polymerization (ROMP) and atom transfer polymerization (ATRP) [80,81]. The bifunctional catalyst A was designed to promote both ROMP of cyclooctadiene (COD) and ATRP of methyl methacrylate (MMA). Thus, catalyst A was employed to perform both polymerizations in one pot leading to diblock polybutadiene/polymethylmethacrylate copolymer (58-82% yield, PDI = 1.5). After polymerization the reaction vessel was exposed to hydrogen (150 psi, 65 °C, 8h), under conditions for Ru(H2)(H)Cl(PCy3)2 to be produced, and the hydrogenation of diblock copolymer could attain 95% [82] (Scheme 36). 

Brushes with diblock side chains have been prepared by the same concept as illustrated in Figure 13. In this case either a polystyrene block or a poly-(n-butylacrylate) block was grafted first by atom transfer polymerization, ATRP, on a poly(2-bro-mopropanoyl ethyl methacrylate), pBPEM, on which in a second step the other monomer was polymerized as the second block.189 Table 4 summarizes the molecular structure of the corresponding polymers, i.e., (i) the macroinitiator or mere backbone molecule (pPBEM) from which (ii) a brush with pnBuA homopolymer side chains (pBPEM-g—pnBuA), (iii) a... 

The discovery of the controlled radical polymerization (CRP) offered additional possibilities in the chemistry of TPEs [52-54]. CRP was used in both graft and block copolymer preparation and extensively reviewed by Matyjaszewski [55] and Mayes et al. [56]. It allows the easy preparation of novel environmentally friendly materials, such as polar TPEs it can be carried out in the bulk or in water and requires only a modest deoxygenation of the reaction mixture. Atom transfer polymerization (ATRP) is one of the most important aspects of CRP it was developed by Matyjaszewski and rests on an equilibrium between active and dormant species [57]. Moineau et al. [58] applied ARTP to the preparation of poly(methyl methacrylate-6-n-butyl acrylate-6-methyl methacrylate). 

Although copper reagents, hahdes and triflates, are widely used in atom-transfer polymerization reactions (ATRP) [63], these processes do not fall under the category of Lewis acid-mediated reactions. Sherrington and co-workers have shown that a vinyl monomer coordinated to a chiral copper Lewis acid (122) undergoes stereoselective polymerization (Sch. 29) [64]. A chiral block-copolymer 124 was prepared under radical conditions. 

Fontaine and coworkers have recently reported the synthesis of a supported aza-lactone via atom radical transfer polymerization (ATRP) [9]. This method involved the preparation of a Wang resin-supported initiator, followed by subsequent ATR polymerization between 2-vinyl-4,4-dimethyl-5-oxazolone (VAZ) and styrene to generate several macroporous, aza-lactone functionalized resins with different architectures. These were shown to scavenge benzyl amines in a highly efficient fashion (Scheme 8.5). 

Describe and illustrate atom transfer polymerizations controlled by copper/bipyridine complex and by carbon tetrachloride, dichloro(triphenyl-phosphine)-mthenium(ll), and methylaluminum bis(2,6-di-ferf-butyl-phenoxide). Explain what ARGENT)ATRP and SET-LRP) mean. Illustrate the proposed Percec mechanism and the Matyjaszewski mechanisms. 

We have seen previously that polymerization initiated by free-radicals suffers from some disadvantages. Mainly, the chain-length cannot be controlled and branching occurs. Some of these disadvantages are overcome in newer methods of radical polymerization. An important new development in this regard is the atom transfer radical polymerization (ATRP) [29-30]. In this process all the chains are initiated essentially at the same time (at the point of catalyst injection) and all the chains grow at the same rate until the monomer is consumed. The important principles of the atom transfer polymerization process are illustrated by the following sequence of reac-... 

Enantioselective Radical Polymerization. The 2,2 -azo(bis)isobutyronitrile/copper(n) triflate/chiral diamine ligand system was used as an asymmetric reverse atom transfer polymerization initiating system for the enantiomer-selective cyclopolymerization of (25,4S 2/ ,4/5-2,4-pentanediyl dimethacrylate. Results indicate that the asymmetric reverse ATRP initiating system was effective for the enantioselective radical cyclopolymerization, leading to optically active polymers. Three different chiral diamines were used as ligand including (—)-sparteine. 

BMIm][PF6] l-Butyl-3-methylimidazolium hexafluorophosphate ATRP Atom transfer polymerization... 

The facile and reversible reaction of propagating species with transition metal halide complexes to form a polymeric halo-compound is one of the key steps in atom transfer radical polymerization (ATRP, see Section 9.4). 

The first reports of ATRP (Atom Transfer Radical Polymerization), which clearly displayed the characteristics of living polymerization, appeared in 1995 from the Laboratories of Sawamoto,2 Matyjaszewski266 and Percec.267 The literature on ATRP is now so vast that a comprehensive review cannot be... 

Polystyrene-Woc -polysulfone-/ /oc -polystyrene and poly(butyl acrylate)-Woc -polysulfone-/ /oc -poly(butyl acrylate) triblock copolymers were prepared using a macroinitiator.214 The hydroxyl-terminated polysulfone was allowed to react with 2-bromopropionyl bromide, an atomic transfer radical polymerization (ATRP) initiator, in the presence of pyridine. The modified macroinitiator could initiate die styrene polymerization under controlled conditions. 

Brzezinska KR, Deming TJ (2004) Synthesis of AB diblock copolymers by atom-transfer radical polymerization (ATRP) and living polymerization of alpha-amino acid-N-carboxyan-hydrides. Macromol Biosci 4 566—569... 

In 2003, the van Hest group produced elastin-based side-chain polymers [123]. This research was motivated by the demonstration of the occurrence of an inverse temperature transition in a single repeat of VPGVG [124]. A methacrylate-functionalized VPGVG was synthesized and used as a monomer to perform atom transfer radical polymerization (ATRP) to produce homopolymers (Fig. 16b) or... 

Star polymers are a class of polymers with interesting rheological and physical properties. The tetra-functionalized adamantane cores (adamantyls) have been employed as initiators in the atom transfer radical polymerization (ATRP) method applied to styrene and various acrylate monomers (see Fig. 21). 

Figure 21. Atom transfer radical polymerization (ATRP) synthetic route to tetrafunctional initiators of a star polymer with adamantyl (adamantane core). Taken from Ref. [91] with permission.

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