Polystyrene ATRP

The majority of polymers formed by living radical polymerization (NMP, ATRP, RAFT) will possess labile functionality at chain ends. Recent studies have examined the thermal stability of polystyrene produced by NMP with TEMPO (Scheme 8.3),2021 ATRP and RAFT (Scheme 8.4).22 In each case, the end groups... 

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. 

Block copolymers were synthesized by a combination of fipase-catalyzed polymerization and atom transfer radical polymerization (ATRE). " " At first, the polymerization of 10-hydroxydecanoic acid was carried out by using lipase CA as catalyst. The terminal hydroxy group was modified by the reaction with a-bromopropionyl bromide, followed by ATRP of styrene using CuCE2,2 -bipyridine as catalyst system to give the polyester-polystyrene block copolymer. Trichloromethyl-terminated poly(e-CL), which was synthesized by lipase CA-catalyzed polymerization with 2,2,2-trichloroethanol initiator, was used as initiator for ATRP of styrene. 

Polystyrene/polyethylene oxide dendrimers were prepared by ATRP using tri- and tetra (bromomethyl) benzene as the initiators [207]. Each bromine end-group of the resulting stars was transformed first to two - OH groups and subsequently to potassium alcholate, as shown in Scheme 114. These - OK sites served to initiate the anionic polymerization of EO. The synthesized dendritic copolymers were found to display monomodal and narrow molecular weight distribution. 

ARGET ATRP has been successfully applied for polymerization of methyl methacrylate, ft-butyl acrylate and styrene in the presence of Sn(EH)2 (10 mol% vs. alkyl halide initiator or 0.07 mol% vs. monomer) [164,165]. For all monomers, polymerizations were well controlled using between 10 and 50 ppm of copper complexes with highly active TPMA and Me6TREN ligands. ARGET ATRP has also been utilized in the synthesis of block copolymers (poly(n-butyl acrylate)— -polystyrene and polystyrene-Z -poly(n-butyl acrylate) [164,165] and grafting... 

He also prepared a poly(styrene-g-styrene) polymer by this technique [114], The lack of crosslinking in these systems is indeed proof of the control achieved with this technique. An eight-arm star polystyrene has also been prepared starting from a calixarene derivative under ATRP conditions [115]. On the other hand, Sawamoto and his coworkers used multifunctional chloroacetate initiator sites and mediation with Ru2+ complexes for the living free-radical polymerization of star poly(methylmethacrylate) [116,117]. More recent work by Hedrick et al. [84] has demonstrated major progress in the use of dendritic initiators [98] in combination with ATRP and other methodologies to produce a variety of structure controlled, starlike poly(methylmethacrylate). 

The properties of the hybrid diblock structures can be altered drastically by simply taking advantage of the high terminal functionality of the dendritic block. For example unusual diblock structures useful for the modification of surfaces have been prepared by ATRP of polystyrene (PS) initiated from the benzylic halide focal point of Frechet-type dendrons with terminal isophthalate ester groups [9b], Well-defined copolymers with narrow molecular weight distributions were obtained and excellent agreement was observed between calculated... 

P. Zhou, G. Q. Chen, C. Z. Li, F. S. Du, Z. C. Li, F. M. Li, Synthesis of hammerlike macromolecules of C60 with well-defined polystyrene chains via atom transfer radical polymerization (ATRP) using a C60-monoadduct initiator, Chemical Communications, pp. 797-798, 2000. 

Briefly, norbornene-derivatized silica was first reacted with Mo(N-2,6-i-Pr2-C6H3)(CHCMe2Ph)(OCMe(CF3)2)2, followed by (4 -(norbom-2-en-5-ylmethylen-oxy)terpyridine). Loading with Cu (I) afforded the desired ATRP support [18, 22-24], Typical metal loadings were in the range of 15 mmolg. Polystyrene (PS) obtained with these supports under ATRP-conditions showed comparably low poly-dispersities (PDI = 1.55-1.77). The ATRP system consisted of a metal center with one terpyridyl and presumably three acetonitrile ligands, which were at least in part substituted by monomer. Consequently, in contrast to standard systems [25], the equilibrium in this type of reaction did not require conformational... 

Dynamic formation of graft polymers was synthesized by means of the radical crossover reaction of alkoxyamines by using the complementarity between nitroxide radical and styryl radical (Fig. 8.13) [40]. Copolymer 48 having alkoxyamine units on its side chain was synthesized via atom transfer radical polymerization (ATRP) of TEMPO-based alkoxyamine monomer 47 and MMA at 50°C (Scheme 8.9). The TEMPO-based alkoxyamine-terminated polystyrene 49 was prepared through the conventional nitroxide-mediated free radical polymerization (NMP) procedure [5,41], The mixture of copolymers 48 and 49 was heated in anisole... 

The grafting-through method has also been studied for ATRP. Vinyl chloroacetate is used as the initiator in ATRP of a monomer such as styrene to produce a macromonomer. Vinyl chloroacetate does not significantly copolymerize with styrene, and the result is a polystyrene vinyl macromonomer, which is then polymerized to a brush polymer [Davis and Matyjaszewski, 2002],... 

Sha et al. applied the commercially available dual initiator ATRP-4 for the chemoenzymatic synthesis of block copolymers. In a first series of publications, the group reported the successful synthesis of a block copolymer comprising PCL and polystyrene (PS) blocks [31, 32]. This concept was then further applied for the chemoenzymatic synthesis of amphiphilic block copolymers by macroinitiation of glycidyl methacrylate (GMA) from the ATRP functional PCL [33]. This procedure yielded well-defined block copolymers, which formed micelles in aqueous solution. Sha et al. were also the first to apply the dual enzyme/ATRP initiator concept to an enzymatic polycondensation of 10-hydroxydecanoic acid [34]. This concept was then extended to the ATRP of GMA and the formation of vesicles from the corresponding block copolymer [35]. 

McCullough and coworkers had synthesized block copolymers of poly(3-hexylthiophene) and polystyrene or PMA by ATRP of the vinyl monomer from a polythiophene macroinitiator, which was prepared in several steps... 

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... 

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