Successive Synthesis of Miktoarm Star Polymers Having up to Seven Arms by a New Iterative Methodology Based on Living Anionic Polymerization Using a Trifunctional Lithium Reagent

A new stepwise iterative methodology based on living anionic polymerization using a trifunctional lithium reagent substituted with trimethylsilyl (TMS), tert-butyldimethylsilyl (TBDMS), and tetrahydropyranyl (THP) ethers of protected hydroxyl functionalities has been developed in order to obtain synthetically challenging many-armed μ-star polymers. In each reaction sequence of the new methodology, these three ether functions were selectively deprotected in turn under carefully selected conditions as designed, followed by conversion to three α-phenyl acrylate (PA) reaction sites step by step at different reaction stages. They were used for the introduction of two different arm segments and the reintroduction of the above same three ethers. This reaction sequence was repeated three times to successively synthesize 3-arm ABC, 4-arm ABCD, 5-arm ABCDE, 6-arm ABCDEF, and 7-arm ABCDEFG μ-star polymers with well-defined structures. Herein, the A, B, C, D, E, F, and G arms were poly(cyclohexyl methacrylate), polystyrene, poly(4-methoxystyrene), poly(4-methylstyrene), poly(methyl methacrylate), poly(ethyl methacrylate), and poly(2-methoxyethyl methacrylate) segments, respectively. The trifunctional lithium reagent was also demonstrated to satisfactorily function as a convenient and useful core agent access to the general synthesis of 4-arm ABCD and 6-arm A2B2C2 μ-star polymers.