Precise Synthesis of New Exactly Defined Graft Copolymers Made up of Poly(alkyl methacrylate)s by Iterative Methodology Using Living Anionic Polymerization

Abstract

An iterative methodology using living anionic polymerization with a 1,1-diphenylethylene disubstituted with trimethylsilyl (TMS) and tert-butyldimethylsilyl (TBS) ethers has been developed in order to synthesize new exactly defined graft copolymers made up of poly(alkyl methacrylate)s. During each reaction sequence, the TMS and TBS ethers were transformed into α-phenyl acrylate (PA) functions one by one at the different reaction stages. The first PA function derived from the TMS ether was utilized to introduce the graft chain, while the main chain with the TMS and TBS ethers was introduced via the second PA function derived from the TBS ether. Thus, the same chain-end functionalities (both TMS and TBS ethers) were reintroduced after construction of the graft unit. In practice, the reaction sequence involving “the introduction of the graft chain” and “the introduction of the main chain with the two silyl ethers” was iterated three times, leading to the synthesis of poly(benzyl methacrylate) (PBnMA)-exact graft-poly(methyl methacrylate) (PMMA) with three PMMA graft chains. Similarly, the synthesis of PBnMA-exact graft-poly(2-vinylpyridine) (P2VP) with two P2VP graft chains was successfully carried out. With the use of the α,ω-chain-end-difunctionalized PBnMA as the starting material, two graft units could be constructed at the same time by iterating the reaction sequence once. The graft copolymers with up to six graft chains were obtained by only three repeated reaction sequences. Thus, the reaction steps could be significantly reduced. The graft copolymers synthesized in this study were perfectly controlled in structure from a viewpoint of the following three parameters defining the structure of the graft copolymer: (1) molecular weight of the main chain, (2) molecular weights of the graft chains, and (3) number and placement of the graft chains. Furthermore, these three parameters can also be intentionally changed as required.