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The chloromagnesium exchange of 4-chlorostyrene provides an easy access to a new versatile polymerizable 2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO)-based nitroxide. Indeed, first, its alkoxyamine based on the α-methyl benzyl radical fragment efficiently mediates the polymerization of styrene (respectively n-butyl acrylate) to yield branched polystyrene [respectively poly(n-butyl acrylate)] with alkoxyamine function as branch point and well-defined branches. Second, the self-condensing of this polymerizable nitroxide by manganese coupling affords a mixture of oligomeric linear polyalkoxyamines. Polymerization of styrene mediated with these polyalkoxyamines gives multiblock polystyrenes with alkoxyamine group as linker between polystyrene blocks and exhibits the following features: the synthesis of the polystyrene blocks is controlled as their average molecular weight Mn(block) increases linearly with conversion and their average dispersity Mw/Mn(block) decreases with it. At a given temperature, the molecular weight and the dispersity of the polyalkoxyamines weakly impact Mn(block) and Mw/Mn(block). In contrast, the molecular weight of the multiblock polystyrene increases linearly with conversion until reaching a constant value. The number of block is independent of the molecular weight of the polyalkoxyamines. These unusual results can be explained by the fact that during polymerization, mediating TIPNO-based polymeric nitroxides with different lengths are generated and are exchanged. Finally the dispersity of the multiblock polystyrene is quite broad and lies between 1.7 and 2.8. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 |
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