Anionic polymerization and termination

Narrowly distributed Pl-ft-PS-i-PI triblock copolymer chains with both of their ends capped with bromobutyl groups were prepared by sequential addition of living anionic polymerization and terminated by excess of 1,4-dibromobutane (PS block Mw = 3.5 x 103 g/mol PI blocks Mw = 3.1 x 103 g/mol Mw/Mn = 1.12 The degree of end-functionalization was 92% characterized by HNMR). Figure 6 shows the SEC profile of such prepared triblock copolymer chains. The small but a detectable amount ( 5%) of Pl-i-PS-i-PI dimers, PI-Z>-PS-Z>-PI-c-PI-Z>-PS-Z>-PI, is presumably formed via the Wurtz-type coupling reaction. 

Star polymers are the simplest of the branched polymers they represent polymers wherein several linear chains are linked to a single multivalent molecular core 3-arm, 4-arm, and even 12-arm star polymers have been synthesized [43]. Typically, the most efficient process to prepare such polymers is to use a living polymerization, such as anionic polymerization, and terminate the process by a nucleophilic substitution reaction onto a multifunctional core. With the advent of CRPs and the CuAAC reaction, Gao and Matyjaszewski utilized, for the first time, a combination of ATRP and click reaction to prepare star-branched polymers [44] as described earlier, ATRP can be readily used to prepare azide-terminated polystyrene by transforming the terminal bromide, which is typically installed at one chain end during ATRP, to an azide. The PS-azide was then reacted with different core molecules bearing multiple propargyl groups an example is the... 

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