Inifer, iniferter techniques

The inifer technique is specific for cationic and radical polymerizations. The most frequently used inifers in the first case are 1-chloro-l-methyl-ethylbenzene (a) 1,4-bis( 1-chloro-l-methylethyl)benzene (6) and l,3,5-tris(l-chloro-l-methyl)benzene (c) 

With 2-methylpropene as M, both linear and star macromers have been prepared [92-94]. Many kinds of inifers may, of course, be used. For example Kress and Heitz prepared macromers from poly(oxytetramethylene) chains with acrylate or methacrylate end groups, by THF polymerization initiated by superacids with anhydrides as co-initiators - transfer agents [95]. 

The Inifer technique enables us to fulfil some requirements of polymer architecture even in some radical processes. An amplified form may be applied, the Iniferter variant, where the radical initiator simultaneously acts as a transfer and terminating agent. Otsu et al. used sulphides and disulphides (tetraethylthiuram disulphide, PhSSPh, Ph2S, PhCH2SSCH2Ph) [96] and carbamates (benzyl-A,A-diethyldithiocarbamate, p-xylylene-A,7V-diethyl-dithiocarbamate) [97] in the photopolymerization of methyl methacrylate and styrene, and phenylazotriphenylmethane in the polymerization of methyl methacrylate [98]. Living radical polymerizations yield polymers with defined end groups or the required block copolymers. 

Allen and C. R. Patrick, Kinetics and Mechanisms of Polymerization Reactions, Horwood, Chichester, 1974, pp. 144, 145. 

Bamford, W. G. Barb, A, D. Jenkins and P. F. Onyon, The Kinetics of Vinyl Polymerization by Radical Mechanisms, Butterworths, London, 1958. 

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Probably the first publication that dealt with LRP already appeared in the late 1960s (3). In the 1970s and 1980s it was realized that the main drawback in FRP, ie, the broad polydispersities, and the inability to form block copolymers could be overcome by the introduction of reversible deactivation of the active radical. Otsu reported on several attempts to introduce this reversibility (4,5). The inifer-ter technique was developed, which comprises a UV-labile or thermally labile link that can be reversibly cleaved, and used for monomer insertion (6,7). Otsu showed that the technique allowed the synthesis of block copolymers, albeit with a PDI around 2. Currently it turns out that the iniferter technique may still have advantages over the more recent developments, eg when the synthesis of multiblock copolymers is aimed for (8). 

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