Synthesis of novel block polymers with unusual block sequences by methodology combining living anionic polymerization and designed linking chemistry

This article reviews the various developments of a new methodology combining the living anionic polymerization and a designed linking chemistry for the synthesis of block polymers using two, two of three, three, or four monomers with different reactivities. With this methodology, a number of well-defined triblock copolymers, triblock terpolymers, tetrablock quaterpolymers, and multiblock copolymers with alternating two segments have been successfully synthesized. The obtained polymers were all novel well-defined block polymers with unusual block sequences. More importantly, they are definitely inaccessible by the sequential polymerization using monomers with different reactivities. The monomers used in the synthesis were mainly styrene, 2-vinylpyridine, and methyl (or tert-butyl) methacrylate classified into three categories by their reactivities. In addition, 1,2-butylene oxide was used as the fourth monomer to synthesize the tetrablock quaterpolymers. There are also a number of other monomers classified into each of these categories, which can be readily replaced from the main monomers. By developing the methodology using these monomers, it becomes possible to synthesize a far more number of block polymers beyond our imagination. In practice, several synthetic feasibilities are described in each chapter. The key for this synthetic success is to suitably choose an alpha-phenylacrylate function used as the reaction site, capable of quantitatively linking with each of the living anionic polymers having a wide range of reactivity, which makes it possible to connect two different polymer segments difficult to access by the sequential polymerization. One more important issue is to employ the iterative linking process, which enables the successive synthesis of alternating multiblock copolymers of up to the decablock type and possibly with more blocks. Generality, versatility, and advantages of the proposed methodology have been demonstrated throughout the synthesis of the block polymers.