Re(V)-Mediated Living Radical Polymerization of Styrene: ReO₂I(PPh₃)₂/R−I Initiating Systems

Abstract

Rhenium(V) iododioxobis(triphenylphosphine) [ReO2I(PPh3)2] proved an effective metal catalyst for living radical polymerization of styrene in conjunction with alkyl iodide as an initiator [R−I: CH3CH(Ph)I, (CH3)2C(CO2Et)I, and CH3CH(CO2Et)I] in the presence of Al(Oi-Pr)3. Compared to RuCl2(PPh3)3, the group 7 complex was highly effective for styrene, so as to induce the living polymerization even at 30 °C to yield well-controlled polystyrene, with M̄ n up to ∼4 × 104 and very narrow molecular weight distributions (MWDs) (M̄ w/M̄ n = 1.19). The polystyrene thus obtained possessed one initiator moiety (R) at the α-end and one iodine atom at the ω-end, both from the initiator R−I, which indicates that the polymerization proceeds via activation of the C−I terminal, derived from R−I, by the Re(V) complex. Addition of methanol or water did not inhibit these polymerizations, while a stable nitroxide radical (TEMPO) immediately and completely quenched them. The quenching experiments thereby supported intervention of radical species in the Re(V)-mediated living polymerization.

Synthesis of Amphiphilic Polystyrene-b-Poly(acrylic acid) Diblock Copolymers by Iodide-Mediated Radical Polymerization

“…The peaks at 4.51 to 4.65 ppm were ascribed to the methine proton (b) at the !-end adjacent to the iodine atom. 36 Furthermore, the ratio of I a =I b was 1:1.18, which was close to 1:1, where I a and I b are the integral values of methine proton at the -end derived from CHI 3 and that at the !-end adjacent to the iodine atom, respectively, indicating that the obtained polystyrene indeed had CHI 3 moiety at one end and an iodine atom at the other end.…”

In situ bidentate to tetradentate ligand exchange reaction in cobalt-mediated radical polymerization

“…Numerous transition metals including nickel [23], titanium [24,25], molybdenum [26,27], osmium [28,29] cobalt [30] and rhenium [31] are effective for ATRP [32]. This family is however dominated by ruthenium [33][34][35], iron [36][37][38][39] and copper complexes [10,21,28,[40][41][42][43][44].…”

Controlled Photoradical Polymerization Mediated by 2,2,6,6-Tetramethylpiperidine-1-Oxyl

“…Examples of controlled radical polymerizations include: iniferter polymerization [2]; reversible addition fragmentation chain transfer polymerization (RAFT) [3]; atom transfer radical polymerization (ATRP) using transition metal complexes, such as Cu [4], Ni [5], Co [6], Fe [7], Ru [8], Rh [9], Pd [10], and Re [11]; iodide-transfer polymerization [12][13][14]; and nitroxide-mediated polymerization (NMP) [15,16]. The primary significance of these controlled/living radical polymerizations lies in the fact that the polymerizations can produce precisely designed architectures.…”