This article reviews the successful development of two specially designed linking methodologies in conjunction with a living anionic polymerization system for the synthesis of novel multiblock polymers, composed of three or more blocks, difficult to be synthesized by sequential polymerization. The first methodology with the use of a new heterofunctional linking agent, 2-(4-chloromethylphenyl)ethyldimethylchlorosilane (1), was developed for the synthesis of multiblock polymers containing poly(dimethylsiloxane) (PDMS) blocks. This methodology is based on the selective reaction of the chain-end silanolate anion of living PDMS, with the silyl chloride function of 1, and subsequent linking reaction of the resulting ω-chain-end-benzyl chloride-functionalized polymer with either a living anionic polymer or living anionic block copolymer. With this methodology, various multiblock polymers containing PDMS blocks, up to the pentablock quintopolymer, were successfully synthesized. The second methodology using an α-phenylacrylate (PA) reaction site was developed for the synthesis of multiblock polymers composed of all-vinyl polymer blocks. In this methodology, an α-chain-end-PA-functionalized polymer or block copolymer, via the living anionic polymerization, was first prepared and, then, reacted with appropriate living anionic polymer or block copolymer to link the two polymer chains. As OPEN ACCESSPolymers 2013, 5 1013 a result, ACB (BCA), BAC (CAB), (AB) n , (AC) n , ABA, ACA, BCB, and ABCA multiblock polymers, where A, B, and C were polystyrene, poly(2-vinylpyridine), and poly(methyl methacrylate) segments, could be successfully synthesized. The synthesis of triblock copolymers, BAB, CAC, and CBC, having molecular asymmetry in both side blocks, was also achieved. Furthermore, the use of living anionic polymers, derived from many other monomers, categorized as either of styrene, 2-vinylpyridine, or methyl methacrylate in monomer reactivity, in the linking methodology enabled the number of synthetically possible block polymers to be greatly increased. Once again, all of the block polymers synthesized by these methodologies are new and cannot be synthesized at all by sequential polymerization. They were well-defined in block architecture and precisely controlled in block segment.

This study demonstrates the versatility and wider applicability of the recently developed methodology combining the living anionic polymerization with a specially designed linking reaction using the α-phenylacrylate (or benzyl bromide) function, allowing the synthesis of triblock co-and terpolymers, which are otherwise diffi cut to be obtained by sequential addition of monomers during a sequential polymerization approach. With this methodology using styrene and four para -substituted styrene derivatives with N -cyclohexylimine, 4-N,N -dimethyl-2-oxazoline, 2,6-di( tert -butyl)-4-methylphenyl ester, and nitrile, 12 polymers among the 16 possible triblock terpolymers and 6 triblock copolymers were successfully synthesized. Furthermore, the synthesis of two tetrablock quarterpolymers was achieved by the same linking methodology. The polymers synthesized in this study are all well-controlled in chain length, composition, which are diffi cult to be obtained by the sequential polymerization. In addition, they possess functional groups usable for the further modifi cation and introduction of other functionalities.

Back Cover: Well‐defined triblock co‐ and terpolymers, which are difficult to be obtained by sequential monomer addition to anionic initiator, was precisely synthesized by the methodology combining the living anionic polymerization with a specially‐designed linking reaction using a‐phenylacrylate function. Further details can be found in the article by Yuri Matsuo,* Ryuji Konno, Raita Goseki, Takashi Ishizone, and Akira Hirao* on page 622.