Controlled Radical Polymerization Initiated by Solvated Electrons

Abstract

Solvated electron (esol−) is highly reducing species and apt to initiate monomers via one‐electron transfer reaction. Herein, utilizing the esol− solution of Na/hexamethylphosphoramide, radical and anionic initiations were observed respectively, which heavily depended on Na concentrations. Interestingly, this initiation system, in states of lower Na concentrations, higher molar conductivities and less paired esol−, gave rise to a controlled radical polymerization (CRP) to yield polymers with predictable molecular weights and narrow molecular weight distributions (the lowest Ð = 1.25). This CRP presented unique behaviors, like solvent effect, electric field effect and unusual copolymerization phenomenon. A semi‐conjugated radical carrying a negative charge is proposed to be responsible for the CRP. This system gives a distinct way to regulate CRP from current CRPs, and offers new insights into the monomer initiation by esol−.This article is protected by copyright. All rights reserved

Electric Field Effect of the Plasma-Initiated Polymerization of Methyl Methacrylate: A Negatively Charged Long-Lived Radical

“…Such an Ep result, however, is close t of PMMA in a RP [21], regardless of the negatively charged nature of the growing ra in the PIP. In addition, this Ep value is similar to that of PMMA detected in the so electron-initiated polymerization [18]. Therefore, the PIP gave a normal Ep value but propagating constant (kp), like the case that occurred in the solvated electron-ini polymerization.…”

“…Moreover, it is worth mentioning that these unique polymerization behaviors also appeared in the polymerization initiated by samarium diiodide (SmI 2 ) [18], a typical one-electron transfer agent [20]. It is noted that the polymer migration in the PIP behaved like it had taken pl the solvated electron-initiated polymerization under the electric field [18]. An almost tical mass ratio curve to that of PIP (Figure 2b) was seen in the latter polymerizati addition to the electric field effect, however, both polymerizations presented other mon features, such as a long-lived radical, solvent effect (Figure S2), and a low prop ing constant (kp = 10 [11][12][13]16,18], which do not comply with the tional radical mechanism.…”

“…Benefiting from the coulombic repulsion between the negatively charged radicals, the polymerization could maintain a higher radical concentration (~10 −3 mol/L) and, hence, presented a higher rate close to that of RP, despite its low k p value [18]. Moreover, it is worth mentioning that these unique polymerization behaviors also appeared in the polymerization initiated by samarium diiodide (SmI 2 ) [18], a typical one-electron transfer agent [20]. It is noted that the polymer migration in the PIP behaved like it had taken pl the solvated electron-initiated polymerization under the electric field [18].…”

“…These analyses reveal that PIP yielded polymers with chemical constitutions similar to the PMMA produced by RP, although the polymerization started from a negatively charged radical and was conducted in a DC electric field. The tacticity of the polymers was calculated according to the split peaks of the αmethyl group at 1.26-0.84 ppm [18], as shown in Figures 8, S5 and Table 2. The PIP in the electric field gave similar tacticity data to those by the RP, when they both inclined to a syndiotactic addition of MMA.…”

“…In the RP of MMA, the preference for a syndiotactic placement can be interpreted by the α-methyl repulsion between growing chains and incoming monomers [19], even if a traditional radical generally leads to an atactic addition due to the planar sp 2 configuration. In the solvated electron-initiated polymerization of MMA, The tacticity of the polymers was calculated according to the split peaks of the αmethyl group at 1.26-0.84 ppm [18], as shown in Figures 8 and S5 and Table 2. The PIP in the electric field gave similar tacticity data to those by the RP, when they both inclined to a syndiotactic addition of MMA.…”