Living radical copolymerization

One of the major advantages of radical polymerization over most other forms of polymerization, (anionic, cationic, coordination) is that statistical copolymers can be prepared from a very wide range of monomer types that can contain various unprotected functionalities. Radical copolymerization and the factors that influence copolymer structure have been discussed in Chapter 7. Copolymerization of macromonomers by NMP, ATRP and RAFT is discussed in Section 9.10.1. 

An issue in living radical copolymerization is that the conditions for dormant chain activation can vary substantially according to the particular propagating radical. The problem may be mitigated by two factors. 

Although, there are reports on differences in reactivity ratios observed for conventional radical copolymeri/.ation vs living radical copolymerization or RAKT ), most research suggests that reactivity ratios are identical and any discrepancies in composition should be attributed to other factors. 

In comparing observed reactivity ratios between various polymerization systems, it is important to take into account the possible effect of molecular weight on copolymer composition. In conventional radical copolymerization, the specificity shown in the initiation and termination steps can have a significant effect on the composition of low molecular weight copolymers (usually 10 units). These effects are discussed in Section 7,4.5. In a living polymerization molecular weights are low at low conversion and increase with conversion. In these 

One might also anticipate that the influence of bootstrap effects (Section 

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Matyjaszewski and coworkers 190,191 have explored living radical copolymerization (ATRP and RAFT) in the presence of Lewis acids. 

The grafting through approach involves copolymerization of macromonomers. NMP, ATRP and RAFT have each been used in this context. The polymerizations are subject to the same constraints as conventional radical polymerizations that involve macromonomers (Section 7.6.5). However, living radical copolymerization offers greater product uniformity and the possibility of blocks, gradients and other architectures. 

Controlled/Living Radical Copolymerization versus Conventional Radical Copolymerization... 

Klumperman and coworkers [259] observed that while it is lately quite common to treat living radical copolymerization as being completely analogous to its radical counterpart, small deviatiOTis in the copolymerization behavior do occur. They interpret the deviations on the basis of the reactions being specific to controlled/living radical polymerization, such as activation—deactivation equilibrium in ATRP. They observed that reactivity ratios obtained from atom transfer radical copolymerization data, interpreted according to the conventional terminal model deviate from the true reactivity ratios of the propagating radicals. 

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. 

P(S- - -BMA) and PS-6-P(S-g - -BMA) block graft copolymers were prepared using TEMPO living and atom transfer radical polymerization techniques (45). The backbone of the P(S-g-f-BMA) copolymer was synthesized by TEMPO living radical copolymerization of styrene and p-chloromethylstyrene. Subsequently, the chloromethyl groups in the presence of CuBr and bipyridine were used as initiation sites of ATRP of t-BMA. In the case of PS-6-P(S-g- -BMA) copolymer, the synthesis was performed in a similar way. 

KOU 09] Koumura K., Satoh K., Kamig.aito M., Mn2(CO)io-induced controlled/living radical copolymerization of vinyl acetate and methyl aciylate Spontaneous formation of block copolymers consisting of gradient and homopolymer segments , Journal of Polymer Science Part A Polymer Chemistry, vol. 47, pp. 1343-1353, 2009. 

Bannister, I., Bilhngham, N.C., Armes, S.P., Rannatd, S.P., Findlay, P. Development of branching in living radical copolymerization of vinyl and divinyl monomers. Macromolecules 39(22), 7483-7492 (2006)... 

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