Symmetric triblock copolymer alternative

An ABA-type triblock copolymer can be obtained by ATRP in two alternative ways, namely, by sequential addition or simultaneous addition of blocks, the former leading to asymmetric and the latter to symmetric triblock copolymers. 

Copolymers are macromolecules consisting of different repeat units here only two types (A,B) of monomers will be considered, and neither regular alternating (ABAB.. .) nor random sequences of these repeat units will be considered, but rather we restrict ourselves to the diblock architecture where a block of Na = fN A-monomers is covalently bonded to a Hock of NB = (1 — ON B-monomers (Fig. 39a). Although triblock and multiblock copolymers have also been synthesized [39,40], they are not considered here. The parameter f is called the composition of the diblock copolymer, and in the case f = 1/2 the diblock copolymer is called symmetric . 

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