We have developed a new iterative methodology using α-chain-end-functionalized living AB diblock copolymer anion as a key building block in order to synthesize a series of well-defined (AB) n multiblock copolymers composed of polystyrene (PS) and poly(methyl methacrylate) (PMMA). The methodology involves the following three reaction steps in the entire iterative synthetic sequence: (1) a sequential living anionic block copolymerization to prepare α-chain-end-functionalized living AB diblock copolymer anion with the 3-tert-butyldimethylsilyloxypropyl (SiOP) group, (2) an introduction of α-phenyl acrylate function (PA) via the SiOP group by deprotection followed by Mitsunobu esterification, and (3) a linking reaction of α-chain-end-PA-functionalized AB diblock copolymer with α-chain-end-SiOP-functionalized living AB diblock copolymer anion. The same iterative synthetic sequence involving the three reaction steps was repeated several times to successively synthesize a series of (AB) n multiblock copolymers (n = 2, 3, 4, and 5) with precisely controlled molecular weights and compositions and very narrow molecular weight distributions (M w/M n ≤ 1.06). Furthermore, different two series of (AB) n multiblock copolymers (n = 2 and 3) composed of PS and either poly(tert-butyl methacrylate) or poly(2-vinylpyridine) blocks were successfully synthesized by the same methodology using the corresponding α-chain-end-SiOP-functionalized living AB block copolymer anions.

This paper reviews the precise synthesis of architectural polymers by methodologies utilizing either chain-end-or in-chain-functionalized AB diblock copolymers as efficient key building blocks. Architectural polymers herein synthesized are miktoarm star-branched polymers, exact graft copolymers, high-density comblike polymers, and alternative and sequential multiblock copolymers. Chain-end-and in-chain-functionalized AB diblock copolymers and, in some cases, core-functionalized ABC star-branched polymers utilized as building blocks are prepared by living anionic polymerization in conjunction with specially functionalized agents and linked in manners suitably designed for each architectural polymer to successfully synthesize such structurally complex polymers. The resulting polymers are all well-defined in structure and precisely controlled in chain length.

Triblock co-and terpolymers with orders of blocks synthetically difficult to be obtained by means of sequential living anionic polymerization were successfully synthesized by developing a new methodology combining living anionic block copolymers with a specially designed linking reaction. The synthesized polymers involve ACB and BAC triblock terpolymers and ABA 0 , ACA 0 , and BCB 0 triblock copolymers, where A, B, and C are polystyrene, poly(2-vinylpyridine), and poly(methyl methacrylate) segments, respectively. The A 0 , A as well as B, B 0 are identical in polymer structure but different in molecular weight. All of them are new type triblock ter-and copolymers with well-defined structures, i.e., predictable molecular weights, compositions, and narrow molecular weight distributions. Transmission electron microscopic studies were performed on bulk morphologies of ACB and BAC triblock terpolymers to exemplarily investigate the influence of changing block sequence and thus changing interfaces. Although both terpolymers showed the tendency to form a lamellaÀlamella morphology, ACB revealed unusually strongly curved lamellae and BAC even undulated lamellae. ' INTRODUCTIONBlock polymers with a high degree of molecular and compositional homogeneity have attracted increasing interest as model polymers to elucidate interesting properties and behavior in combination with morphologies and molecular assemblies. 1À9 Such welldefined block polymers are usually synthesized by means of living anionic polymerization where two or more monomers are sequentially added to appropriate anionic initiators. 10 In fact, well-defined AB diblock copolymers, ABC triblock terpolymers, and (AB) n multiblock copolymers have been successfully synthesized.In order to achieve further design and synthesis of well-defined block polymers by using living anionic polymerization, it is

Five A‐B‐A′, A‐C‐A′, B‐A‐B′, C‐A‐C′, and C‐B‐C′ triblock terpolymers with block orders difficult to synthesize by sequential polymerization have been successfully synthesized by a new methodology combining living anionic polymers with a specially designed linking reaction using α‐phenylacrylate as the reaction site. Here, A(A′), B(B′), and C(C′) represent groups of polymers (having chain‐end anions with different nucleophilicities), which are only polymerizable from A(A′) to B(B′) to C(C′) via sequential polymerization. The corresponding polymers are polystyrene (A) and poly(α‐methylstyrene) (A′), poly(2‐vinylpyridine) (B) and poly(4‐vinylpyridine) (B′) and polymers from methacrylate type monomers like poly(methyl methacrylate) (C), poly(tert‐butyl methacrylate) (C′), poly(2‐hydroxyethyl methacrylate) (C′), poly(2,3‐dihydroxypropyl methacrylate) (C′), and poly(ferrocenylmethyl methacrylate) (C′). Furthermore, three synthetically difficult B‐A‐B, C‐A‐C, and C‐B‐C triblock copolymers with molecular asymmetry in both side blocks have also been synthesized by the developed methodology. All of the polymers thus synthesized are quite new triblock terpolymers and copolymers with well‐defined structures, i.e., precisely controlled molecular weights, compositions and narrow molecular weight distributions (Mw/Mn ≤ 1.05).