Considering crucial problems that limit use of platinum-based fuel cells, i.e. cost and availability, poisoning by fuel impurities and low selectivity, we propose electrocatalysis by enzymes as a valuable alternative to noble metals. Hydrogenase electrodes in neutral media achieve hydrogen equilibrium potential (providing 100% energy conversion), and display high activity in H(2) electrooxidation, which is similar to that of Pt-based electrodes in sulphuric acid. In contrast with platinum, enzyme electrodes are highly selective for their substrates, and are not poisoned by fuel impurities. Hydrogenase electrodes are capable of consuming hydrogen directly from microbial media, which ensures their use as fuel electrodes in treatment of organic wastes.

In a recent article, we have showed that the nitroxide mediated polymerization of methyl methacrylate was possible up to 80% conversion for reasonable masses M n ¼ 60,000 g mol À1 when 2,2-diphenyl-3-phenylimino-2,3-dihydroindol-1yloxyl nitroxide (DPAIO) was used as control agent. We have claimed that the success of this experiment relied on the absence of H-transfer reaction both in the alkoxyamine and between alkyl and nitroxyl radical. In this article, the decomposition of 4-nitrophenyl 2-(2,2,6,6-tetramethylpiperidine-1-yloxy)-2-methylpropionate (1a) and 4-nitrophenyl 2-(2,2-diphenyl-3-phenylimino-2,3-dihydroindol-1-yloxy)-2methylpropanoate (2a) has been studied by 1 H NMR in the presence and in the absence (persistent radical effect condition) of scavenger (thiophenol PhSH). At temperature lower than the one used for polymerization, fast and quantitative H-transfer reaction was observed for 1a whereas no H-transfer reaction was observed for 2a. The scavenging technique proved for the first time that the H-transfer was an intermolecular process for 1a. However, the slow side-reaction of NAOC bond homolysis, which did not impede the control of the polymerization but may exert a detrimental effect on the livingness, was observed and quantified for 2a. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: [6828][6829][6830][6831][6832][6833][6834][6835][6836][6837][6838][6839][6840][6841][6842] 2008

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