Controlled/living radical methods

In order to reduce the contribution of termination processes (Scheme 2.19), controlled/living radical methods establish a fast equilibrium between dormant and active chain ends. Essentially, this equilibrium decreases the relative proportion of propagating radicals and allows them to reversibly deactivate rather than permanently terminate. The radical chain end concentration for CRPs (10 -10" M) is also much less than for ionic polymerizations (10 -10 M). 

In 1995, a new class of controlled/ living radical polymerization methods was reported by the groups of Matyjaszewski [34] and Sawamoto [35], This new process, named atom transfer radical polymerization (ATRP) [34], has had a tremendous... 

A number of controlled/living radical polymerization methods have been developed. These include ... 

While possessing many of the key advantages of controlled/ living polymerization methods, nitroxide-mediated free-radical polymerizations do exhibit several limitations. The range of monomers that have been polymerized using nitroxide-mediated techniques include styrenics. acrylamides and (meth)acrylates but these have predominantly been reported in bulk polymerizations (i.e. without solvent) and are conducted at elevated temperature for long time periods. In addition, synthesis of the unimolecular initiator can prove troublesome (dependent upon the type required) and often requires extensive purification in order to attain sufficient purity levels to allow molecular weight control. 

The synthesis of well-defined macromolecules with structural control can only be achieved by the controlled/living polymerization methods. In addition to the well established anionic [137] and recently developed radical processes [138], living cationic polymerization [139] of appropriate monomers has also been reported. 

The fifty chapters submitted for publication in the ACS Symposium series could not fit into one volume and therefore we decided to split them into two volumes. In order to balance the size of each volume we did not divide the chapters into volumes related to mechanisms and materials but rather to those related to atom transfer radical polymerization (ATRP) and to other controlled/living radical polymerization methods reversible-addition fragmentation transfer (RAFT) and other degenerative transfer techniques, as well as stable free radical pol5mierizations (SFRP) including nitroxide mediated polymerization (NMP) and organometallic mediated radical polymerization (OMRP). 

The first chapter in this volume provides an overview of the current status of controlled/living radical pol5mierization (CRP) systems. The following three chapters discuss important issues relevant to all radical polymerization methods. The mechanistic and kinetic topics of ATRP are... 

VAc has been successfully polymerized via controlled/ living radical polymerization techniques including nitroxide-mediated polymerization, organometallic-mediated polymerization, iodine-degenerative transfer polymerization, reversible radical addition-fragmentation chain transfer polymerization, and atom transfer radical polymerization. These methods can be used to prepare well-defined various polymer architectures based on PVAc and poly(vinyl alcohol). The copper halide/t is an active ATRP catalyst for VAc, providing a facile synthesis of PVAc and its block copolymers. Further developments of this catalyst will be the improvements of catalytic efficiency and polymerization control. 

Controlled living radical polymerization methods were developed to produce polymers with predetermined molecular weights, low polydispersity index, specific... 

Main Controlled/Living Radical Polymerization Methods. 128... 

This article progresses to discuss the newly emerging field of controlled/living radical copolymerization, and the novel materials that can be made using these highly versatile synthetic methods. Finally we cover in brief ionic chain copolymerization and cross-linking copolymerization. 

Figure 11.5 General scheme of SNR-mediated controlled/living radical polymerization methods, [cf. Eq. (11.10) and Fig. 11.4.]...

Segmented terpolymers of poly(alkyl methacrylate)-g-poly(D-lactide)/poly(dimethylsiloxane) (PLA/PDMS) were prepared by combination of a grafting through technique (macromonomer method) and controlled/living radical polymerization such as atom transfer radical polymerization (ATRP) or reversible addition-fragmentation chain transfer polymerization. In a single-step approach, the low molecular weight methacrylate monomer (methyl methacrylate... 

As a unique method of controlled/living radical polymerization, ATRP has had a tremendous impact on the synthesis of macromolecules with well-defined compositions, architectures, and functionalities, including star- and comb-like polymers as well as branched, hyperbranched, dendritic, network, cyclic type structures and so forth. 

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