Graft copolymers grafting from

If a vinyl monomer is polymerized in the presence of cellulose by a free radical process, a hydrogen atom may be abstracted from the cellulose by a growing chain radical (chain transfer) or by a radical formed by the polymerization catalyst (initiator). This leaves an unshared electron on the cellulose chain that is capable of initiating grafting. As cellulose is a very poor transfer agent [10], very little copolymer results from the abstraction of hydrogen atoms by a growing chain radical. The... 

D-funclionali/alion 53 1 6,538 9 graft copolymer synthesis 558-63 grafting from 560 3 grafting through 558-60... 

The grafting from methodology was also utilized for the synthesis of poly(4-methylphenoxyphosphazene-g-2-methyl-2-oxazoline) graft copolymers [187]. The synthetic approach involved the thermal polymerization of hexachlorophosphazene, in the presence of aluminum chloride, to give low molecular weight poly(dichlorophosphazene). The chloro groups were subsequently replaced by 4-methylphenoxy groups, followed by partial bromi-... 

ATRP and grafting from methods led to the synthesis of poly(styrene-g-tert-butyl acrylate)-fr-poly(ethylene-co-butylene)-fr-poly(styrene-g-ferf-butyl acrylate) block-graft copolymer [203]. ATRP initiating sites were produced along the PS blocks by chloromethylation as shown in Scheme 112. These sites then served to polymerize the ferf-butyl acrylate. The poly(ferf-butyl acrylate) grafts were hydrolyzed to result in the corresponding poly(acrylic... 

Scheme 3. Synthetic routes leading to various rod-coil block copolymers via grafting onto" (16a, 16b, 20) or grafting from" (18) reactions.

The copolymer obtained from acrylonitrile, butadiene and styrene is termed as an ABS copolymer. It is a terpolymer. Two methods are used for preparing ABS copolymers such as blending and grafting. These two process produce the copolymers which are different in nature. 

Table 9.4 Characteristics of arborescent polystyrene substrates used in the preparation of isoprene graft copolymers (adapted from ref. 16)...

Table 9.9 Characteristics of PCEYE1-graft-(PS1-block-PCE VE2-graft-PS2) copolymers (adapted from ref. 26)...

Starting from a hyperbranched polyester based on 4,4 -bis(hydroxyphenyl)valeric acid, terminal -OH groups were derivatized to yield the hyperbranched macroinitiator. The Hgand precursor was introduced as the first block in the grafting from reaction, followed by 2-methyl-2-oxazoHne polymerization to give the second block and allow for water-soluble polymers. The triphenylphosphine-functionalized am-phiphihc star block copolymer was obtained after transformation of the iodoaryl... 

In a similar way, the grafting-from technique has been applied to the synthesis of poly(chloroethylvinylether) chains by grafted PCL segments, i.e., po-ly(CEVE-g-CL) graft copolymers. Purposely cationically prepared PCEVE were partially modified by the introduction of 5-10% hydroxyl groups [79]. An equimolar reaction of the pendant hydroxyl functions with HAI/BU2 provided diisobutyl aluminum monoalkoxides dispersed along the polyether backbone. 

In this review, synthesis of block copolymer brushes will be Hmited to the grafting-from method. Hussemann and coworkers [35] were one of the first groups to report copolymer brushes. They prepared the brushes on siUcate substrates using surface-initiated TEMPO-mediated radical polymerization. However, the copolymer brushes were not diblock copolymer brushes in a strict definition. The first block was PS, while the second block was a 1 1 random copolymer of styrene/MMA. Another early report was that of Maty-jaszewski and coworkers [36] who reported the synthesis of poly(styrene-h-ferf-butyl acrylate) brushes by atom transfer radical polymerization (ATRP). 

During the last 5 years, there have been several reports of multiblock copolymer brushes by the grafting-from method. The most common substrates are gold and silicon oxide layers but there have been reports of diblock brush formation on clay surfaces [37] and silicon-hydride surfaces [38]. Most of the newer reports have utilized ATRP [34,38-43] but there have been a couple of reports that utilized anionic polymerization [44, 45]. Zhao and co-workers [21,22] have used a combination of ATRP and nitroxide-mediated polymerization to prepare mixed poly(methyl methacrylate) (PMMA)Zpolystyrene (PS) brushes from a difunctional initiator. These Y-shaped brushes could be considered block copolymers that are surface immobilized at the block junction. 

Graft copolymers of nylon, protein, cellulose, starch, copolymers, or vinyl alcohol have been prepared by the reaction of ethylene oxide with these polymers. Graft copolymers are also produced when styrene is polymerized by Lewis acids in the presence of poly-p-methoxystyrene. The Merrifield synthesis of polypeptides is also based on graft copolymers formed from chloromethaylated PS. Thus, the variety of graft copolymers is great. 

Block and graft copolymers differ from the other copolymers in that there are long sequences of each monomer in the copolymer chain. A block copolymer is a linear copolymer with one or more long uninterrupted sequences of each polymeric species,... 

RAFT has also been used to produce graft polymers. The grafting from method is achieved by reacting a halogen-containing polymer such as styrene p-chloromethy I styrene copolymer with sodium dithiohenzoate to obtain a polymeric dithioester, which is an initiator in RAFT polymerization (Sec. 3-15d) [Quinn et al., 2002]. 

Block Copolymers Grafted from SiOx and Au Surfaces. 124... 

In this article, the use of anionic and cationic surface-initiated methods to form homopolymer and block copolymer brushes grafted from flat and nanoparticle surfaces has been reviewed. The future challenge in understand-... 

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