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

Abstract

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.

Rod–coil type miktoarm star copolymers consisting of polyfluorene and polylactide: precise synthesis and structure–morphology relationship

“…6,[9][10][11][12] Meanwhile, Hirao and coworkers established an iterative route based on the living anionic polymerization to a wide array of miktoarm star copolymers containing two or more different polymer arms. [13][14][15][16][17][18] In addition, the combination of living radical polymerizations and living ring-opening polymerizations have been successfully utilized to create miktoarm star copolymers consisting of various kinds of polymer arms. [19][20][21][22] However, a challenge still exists in the precise synthesis of miktoarm star polymers containing rod-like blocks mainly due to the difficulty in the preparation of the well-defined rod-like polymer segment.…”

Successive Synthesis of Multiarmed and Multicomponent Star‐Branched Polymers by New Iterative Methodology Based on Linking Reaction between Block Copolymer In‐Chain Anion and α‐Phenylacrylate‐Functionalized Polymer

“…Next, the TBDMS ether was deprotected by treatment with Bu 4 NF and phenol, followed by the Mitsunobu esterification reaction with PAA to convert to the PA reaction site. The use of phenol is to prevent decomposition of the star polymer . The resulting core‐PA‐functionalized ABC μ‐star polymer was reacted with the difunctional DPE anion prepared from 1 and sec‐ BuLi at –78 °C for 4 h. Thus, the same TMS and TBDMS ethers were reintroduced as those introduced in the starting PBnMA.…”

“…All chemicals (>98% purities) were purchased from Sigma‐Aldrich Japan or Tokyo Kasei Co. Ltd. and used as received unless otherwise stated. Tetrahydrofuran (THF), heptane, tert ‐butylbenzene, isoprene, styrene, DPE, α‐methylstyrene (αMS), 4‐methylstyrene (MS), 4‐methoxystyrene (MOS), 4‐octylstyrene (OctS), 2‐vinylpyridine (2VP), methyl methacrylate (MMA), benzyl methacrylate (BnMA), and tert ‐butyl methacrylate ( t BMA) were purified according to the procedures reported elsewhere . 3‐ tert ‐butyldimethylsilyloxymethylstyrene (SiOMS), 1‐(3‐ tert ‐butyldimethylsilyloxymethylphenyl)‐1‐(3‐trimethylsilyloxymethylphenyl)ethylene ( 1 ), 1,4‐bis(1‐phenylethenyl)benzene ( 2 ), 1‐(3‐ tert ‐butyldimethylsilyloxymethylphenyl)‐1‐phenylethylene ( 3 ), α‐phenylacrylic acid (PAA), chain‐end‐bromomethyl‐functionalized poly(ferrocenyldimethylsilane) (PFS), and 4‐ tert ‐butyldimethylsilyloxystyrene (SiOS) were synthesized according to the literatures previously reported.…”

“…In order to solve this problem, we have recently developed a “second‐generation” iterative methodology using an α‐phenylacrylate (PA) function as the new reaction site capable of reacting with the less reactive living anionic poly(2‐vinylpyridine) (P2VP) and poly(alkyl methacrylate) (PRMA) . Scheme shows the synthetic outline of a series of μ‐star polymers by the second‐generation iterative methodology.…”

Synthesis of multifunctional ABC stars with a reduction-labile arm by consecutive ROP, RAFT and ATRP processes

“…In route (e), both polymerization and coupling reaction are involved, and precursors to produce the trifunctional agent can be also applied in some cases. highly linking reaction between functional polymers (Scheme 1(c)), in which the popular route lies in iterative methodology involving coupling reaction between living anionic polymer and reactive moiety such as diphenylethylene (DPE), and follows by a second linking reaction between in-situ formed polymeric anion and functional agent to regenerate the reactive functionality into the block junction or functional core via functional group transformation (FGT) [17][18][19][20]. The increased arm number of star polymer in each iterative reaction is equal to the functionality of reactive moiety, and during this process the core is dynamically changeable and gradually formed.…”