Synthesis of Well-Defined (AB)nMultiblock Copolymers Composed of Polystyrene and Poly(methyl methacrylate) Segments Using Specially Designed Living AB Diblock Copolymer Anion

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.