Living radical polymerization definition

This review covers mainly the scientific literature that has appeared in relevant journals until early 2001 concerning the metal-catalyzed (or atom-transfer) living radical polymerization. The word living employed here simply refers to polymerizations that provide control over the molecular weights, the molecular weight distributions, and the chain end reactivity as do other living polymerizations. Its definition and use criteria, along with the word controlled , are still under discussion and have recently been discussed elsewhere.39 Thus, the discussion on the difference between these words is not to be treated here. 

However, there is no definite correlation between the polymerization rate and the redox potential, partly because a higher concentration of the radical species may lead to a higher probability of bimolecu-lar termination and a higher concentration of persistent radical species.54-261 Another possibility of side reaction is due to the reduction of the radical into an anion with metal complexes with extremely low redox potential. An appropriate range for the redox potential of the metal catalysts was suggested between —0.3 and +0.6 V (versus NHE) for living radical polymerization.54... 

The third method is based on a polymer-linking reaction where the liner polymers are obtained by the living radical polymerization with divinyl compounds. This can afford star polymers with a relatively large number of arms, up to several hundred per molecule, while the number of arms by definition involves a statistical distribution in a single sample. 

Other multifunctional initiators include star polymers prepared from initiators via living radical or other living polymerizations. In particular, all of the star polymers via metal-catalyzed living polymerization, by definition, carry a halogen initiating site at the end of each arm, and thus they are potentially all initiators. Thus, star-block copolymers with three polyisobutylene-Mock-PMMA arms and four poly-(THF) -A/oc/F polystyrene or poly(THF)-Woc/c-polysty-rene-Wock-PMMA were synthesized via combination of living cationic and copper-catalyzed living radical polymerizations.381,388 Anionically synthesized star polymers of e-caprolactone and ethylene oxide have... 

Polymerization of vinyl ethers (VE) has been the subject of a considerable amount of theoretical studies. These monomers can be polymerized through radical initiation but the reaction is very slow and leads only to oligomers. Cationic polymerization initiated by a wide variety of Lewis acids is much more efficient and definitely preferred for homopolymer synthesis. Detailed theoretical aspects, and particularly recent developments concerning the controlled/living cationic polymerization of these monomers, have been discussed as well in previous exhaustive review [1,13,98,99] as in the present book (Chapters 4 and 5), and they will no longer be considered here. 

All CRP methods rely on a dynamic equihbration between tiny amounts of propagating radicals and various types of dormant species. The essence of the process is a rapid reversible deactivation of growing radicals. Radicals always terminate and therefore CRP is never living in the pure sense of the living polymerization definition. Indeed, lUPAC recommends to avoid using term Uving for the radical polymerization and suggests to use the term controlled reversible deactivation radical polymerization . 

With [D ] [P ] there is little difference in magnitude between vt and ft hut, as described below, the introduction of ft eliminates the moment closure problem created by the LCB mechanism. These moment definitions collapse the infinite set of equations for polymeric species into a manageable subset, and many of the moments have precise physical meanings. The zeroth live moment, [/cq], is the concentration of polymer radicals in the system (denoted by [Ptot] in Section 3.2.1), and the first live moment, [/ri],is the concentration of monomer units contained in all growing radicals. Similarly, [fo] is the concentration of all polymer chains in the system, and [f i ] is the concentration of monomer units bound in all polymer chains. These values are used to calculate MW averages, where Wn, is the molecular weight of the monomeric repeat unit ... 

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