Precise synthesis of poly(methacrylate)-based miktoarm star polymers by a new stepwise iterative methodology using a formyl-functionalized 1,1-diphenylethylene derivative

A new stepwise iterative methodology using living anionic polymers with a 1,1-diphenylethylene (DPE) derivative substituted with a protected formyl functionality bearing a 1,3-dioxolane (DOL) function, 2, was developed in order to synthesize well-defined μ-star polymers composed of poly(methacrylate)-based arms. In this methodology, the following four reaction steps are involved in the reaction sequence and repeated in each process: (1) the reaction of formyl group with the functionalized DPE anion prepared from 2 and sec-BuLi to generate a hydroxyl group and reintroduce the DOL function at the same time, (2) conversion of the generated hydroxyl group to an α-phenylacrylate reaction site, (3) introduction of the arm segment via the reaction site, and (4) regeneration of the formyl group by deprotection of the DOL function. With the methodology, well-defined 3-arm ABC, 4-arm ABCD, and 5-arm ABCDE μ-star polymers with nearly monodisperse distributions (Mw/Mn ≤ 1.05) were successfully synthesized by repeating the above reaction sequence in each process. Typically, A, B, C, D, and E segments are poly(methyl methacrylate), poly(benzyl methacrylate), poly(allyl methacrylate), poly(6-(4-(4′-cyanophenyl)phenoxy)hexyl methacrylate), and poly(2-tert-butyldimethylsilyloxyethyl methacrylate), respectively.