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Methylmethacrylate (MMA) was polymerized at 25 °C with excimer laser (λ = 308 nm) in the presence of different Co(II) chain transfer agents, bis(boron difluorodimethylglyoximate) cobaltate(II) [Co(dmg-2H)2 (BF2)2] (henceforth called catalyst (1)) and bis(boron difluorodialphafurilglyoximate) cobaltate(II) [Co(afdo-2H)2 (BF2)2] (henceforth called catalyst (2)) used separately, with 2,2′-Azobis-(2-methylpropionitrile) [AIBN] as an initiator. The polymer (PMMA) formed in this study was characterized using GPC, 1H NMR, 13C NMR, and DEPT 135. The value of chain transfer constant (Cs) was higher for catalyst (1) than catalyst (2) by a factor of 5. The higher character of “living free radical polymerization”, as evident from the low values of polydispersity index (PDI), was observed mainly for catalyst (2). Both steric and electronic factors supported by IR and UV–vis spectra for the two catalysts indicate that catalyst (2) is a weaker nucleophile as compared to catalyst (1) forming a weaker Co–C bond between this catalyst and growing polymer chain indicating more living polymerization for the catalyst (2). |
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