Xanthate‐Mediated Controlled/Living Free‐Radical Polymerization under ⁶⁰Co γ‐Ray Irradiation: Structure Effect of O‐Group

Abstract

Summary: The free‐radical polymerizations of vinyl monomers have been studied under 60Co γ‐ray irradiation in the presence of S‐benzyl O‐ethyl dithiocarbonate (X1), S‐benzyl O‐phenyl dithiocarbonate (X2), S‐benzyl O‐2‐naphthyl dithiocarbonate (X3), S‐benzyl O‐(4‐methoxyphenyl) dithiocarbonate (X4), and methyl 4‐{[(benzylthio)carbonothioyl]oxy}benzoate (X5), respectively. The results indicate that the polymerizations of methyl acrylate (MA) reveal good living characteristics in the presence of X2, X3, X4, and X5 with O‐aryl groups, which play an important role in polymerization behavior; large aryl groups lead to slow polymerization. In contrast, the polymerizations with X1 couldn't be controlled and the obtained polymers had a broad‐molecular‐weight distribution or were even cross‐linked. In addition, it was observed that the polymerization of styrene with X2 was a controlled process though it was very slow, and the uncontrolled polymerization of methyl methacrylate (MMA) occurred under γ‐ray irradiation. To the best of our knowledge, this is the first report of xanthates being used as control agents in controlled/living free radical polymerization under γ‐ray irradiation.The structures of the xanthates used here.magnified imageThe structures of the xanthates used here.

Living Radical Polymerization by the RAFT Process—A First Update

“…[71] The paper emphasizes the importance of selecting an irradiation wavelength, the RAFT agent, and the photoinitiator (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, to avoid side reactions such as photodissociation of the RAFT agent. [71] Gamma-initiated RAFT polymerizations of MA in the presence of various dithioesters (including 20, 21, 42, 43b), [87] xanthates [146] and dithiocarbamates, [147] of MMA in the presence of 32, [91] and of NIPAM and AA in the presence of 55 or 61 in aqueous media [110] have been reported.…”

Experimental Requirements for an Efficient Control of Free‐Radical Polymerizations via the Reversible Addition‐Fragmentation Chain Transfer (RAFT) Process

“…MeOVAc [313] EtO-AEMA a,b) [314,315] Sty [19,69,[316][317][318][319] a,b) [320] b) [9,314,315,321] AA [248,322,323] MA [19,324] EA [19,317,325] BA [319,323,325] a,b) [314,315] b) [19,320] tBA [67] Am [322] VAc [19,67,313,[326][327][328][329] b) [330] VPr [327] VPi [328] VND [328] VAGlu [328,331] NVF [332] iPrOVAc [313,333] …”

“…Sty [317] EA [317] PhO-MMA [324] Sty [9,69,324] AA [248] MA [324] a) [335] AAz a) [335] (p-F)PhOVAc [313] (p-HO 2 C)PhOVAc [313] (p-MeO 2 C)PhO-MA [324] VAc [313] (p-MeO)PhO-MA [324] VAc [313] …”

“…d) R 0 can be poly(ethylene glycol) (PEG), [212,276] cellulose, [222] a polyester dendrimer, [221] a polypeptide, [260] or a silica nanoparticle. [217] [9,117,119,324,361] HEMA a) [348] NMAS [76] Sty [9,48,49,67,69,82,84, 107,110,119,133,186, 193,195,197,198,206, 213,216,298,311,324, 336,337,349-352, 361-365, 374,378, 382] a) [225 -227,348] b) [70,71,389] c) [300] MeSty a) [226] StyOCOMe [240] StyMe a) [226] StyOMe a) [226] StyCl a) [226] StyCH 2 Cl [216] StyCH 2 N(Me) 3 Cl [238] 4VP [364] AA [248,323, 366 -370] MA [67,73,119,192,324,336,337,[361][362][363]374,375,383] a) [256,335,379] c) [300] BA <...>…”

“…[72,292] Finally, RAFT polymerizations can be initiated by alternative methods like UV or g-radiation. [79,324,366] UV radiation is able to induce the homolytic cleavage of the weak S-C bond of the CTA. [80,185,224,362] Thus, it can be used to initiate RAFT polymerizations without the need of an added photoinitiator.…”