The general utility of a 1,1-diphenylethylene (DPE) derivative substituted with trimethylsilyl-and tert-butyldimethylsilylprotected hydroxyl functionalities, as a new dual-functionalized core agent in conjunction with a living anionic polymerization system, has been demonstrated by the successful synthesis of various well-defined 3arm ABC and 4-arm ABCD μ-star polymers. Two different protected hydroxyl functionalities were progressively deprotected to generate hydroxyl groups, followed by conversion to α-phenyl acrylate (PA) functions at separate stages, and the PA functions were reacted with appropriate living anionic polymers to result in the above μ-stars. In order to further synthesize μ-star polymers with five or more arms, a new iterative methodology using a functional DPE anion derived from the above DPE derivative has been developed. The reaction system of this methodology is designed in such a way that the PA function used as the reaction site is regenerated after the introduction of an arm segment in each reaction sequence, and this sequence, consisting of "arm introduction and regeneration of the PA reaction site", is repeatable. With this methodology, a series of new well-defined μ-star polymers up to a 5arm ABCDE type, composed of all different methacrylate-based polymer segments, were successfully synthesized for the first time.

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 3arm 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(4methylstyrene), 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 A 2 B 2 C 2 μ-star polymers.

A new type of multi-graft polymers has been successfully synthesized by living anionic polymerization using a difunctional core agent.