Nitroxide mediated living free radical

Hawker CJ, Barclay GG, Orellana A et al. (1996) Initiating systems for nitroxide-mediated living free radical polymerizations synthesis and evaluation. Macromolecules 29 5245-5254... 

Lohmeijer BGG, Schubert US (2004) Expanding the supramolecular polymer LEGO system nitroxide mediated living free radical polymerization for metallo-supramolecular block copolymers with a polystyrene block. J Polym Sci Part A Polym Chem 42 4016-4027... 

Apart from ATRP, the concept of dual initiation was also applied to other (controlled) polymerization techniques. Nitroxide-mediated living free radical polymerization (LFRP) is one example reported by van As et al. and has the advantage that no further metal catalyst is required [43], Employing initiator NMP-1, a PCL macroinitiator was obtained and subsequent polymerization of styrene produced a block copolymer (Scheme 4). With this system, it was for the first time possible to successfully conduct a one-pot chemoenzymatic cascade polymerization from a mixture containing NMP-1, CL, and styrene. Since the activation temperature of NMP is around 100 °C, no radical polymerization will occur at the reaction temperature of the enzymatic ROP. The two reactions could thus be thermally separated by first carrying out the enzymatic polymerization at low temperature and then raising the temperature to around 100 °C to initiate the NMP. Moreover, it was shown that this approach is compatible with the stereoselective polymerization of 4-MeCL for the synthesis of chiral block copolymers. 

Scheme 1.33 Preparation of PS by nitroxide-mediated living free-radical polymerization and its utilization for the functionalization of shortened SWCNTs.

Homopolymer PS and block copolymer poly(tert-butyl acrylate)-b-styrene, prepared by nitroxide-mediated living free-radical polymerization, were utilized for the functionalization of shortened SWCNTs through a radical coupling reaction (Scheme 1.33) [194]. 

Bergbreiter, D. E., Waichuk, B. Meisenheimer Rearrangement of Aiiyi N-Oxides as a Route to Initiators for Nitroxide-Mediated "Living" Free Radical Polymerizations. Macromolecules 1998, 31, 6380-6382. 

III. Nitroxide-Mediated Living Free Radical Polymerizations 3663... 

It is obvious from the above discussion that under the correct conditions and with the appropriate mediating nitroxide free radical, living polymerization conditions can be achieved. On the basis of this realization, numerous groups have demonstrated that the degree of structural control normally associated with more traditional living processes, such as anionic procedures, can be equally applied to nitroxide-mediated living free radical polymerizations. 

Table 2. Structure of Monomer Employed in the Synthesis of Block Copolymers by Nitroxide Mediated Living Free Radical Procedures...

The potential for surface-initiated polymerizations using nitroxide-mediated living free radical procedures is perhaps best illustrated by the direct synthesis of dispersed nanocomposities by Sogah and Giannelis.212 In this approach the synthetic versatility of the alkoxyamine group is again exploited to... 

A similar approach was followed with the eROP of 4-MeCL, followed by nitroxide mediated living free radical polymersation (NMP) of styrene using a bifunctional catalyst (Scheme 11.18) [62]. Styrene, the monomer for the NMP, was added already at the beginning since it proved to be a good solvent for the eROP of lactones. At low temperatures, no radical polymerization occurs thus the two polymerization mechanisms are thermally separated. When the eROP reached a conversion of 50%, a lipase inhibitor, paraoxon, was added to the reaction mixture to prevent further incorporation of the undesired enantiomer. Increasing the temperature to 95 °C started the nitroxide mediated LFRP, to afford block copolymers. After precipitation, the chiral block copolymers obtained showed two Tg s at-51 °C and 106 °C. The specific rotation [a]D25 of the block copolymer was -2.6°. 

Figure 12.9 Block copolymers by one-pot enzymatic ROP and nitroxide-mediated living free-radical cascade polymerization [24].

Georges, M.K., Hamer, G.K., Listigovers, N.A., 1998. Block copolymer synthesis by a nitroxide-mediated living free radical polymerization process. Macromolecules 31 (25), 9087-9089. 

Veregin, R.P.N., Odell, P.G., Michalak, L.M., and Georges, M.K., 1996, Molecular Weight Distributions in Nitroxide-Mediated Living Free Radical Polymerization Kinetics of the Slow Equilibria between Growing and Dormant Chains, Macromolecides, 29 3346... 

Figure 11.8 Random copolymerization of styrene with either (1) methyl methacrylate or (2) butyl acrylate by nitroxide-mediated living free-radical procedures. (Drawn following the synthesis method of ffawker et...

Malmstrom, E., Miller, R. D., and Elawker, C. J. (1997). Development of a new class of rate-accelerating additives for nitroxide-mediated living free radical pol5merization. Tetrahedron, 55(45) 15225-15236. 

Harth, E., et al. (2001). Chain end function in nitroxide-mediated living free radical pol5mierizations. Macromolecules, 54(12) 3856-3862. 

Gotz H, Harth E, Schiller SM, Frank CW, Knoll W, Hawker CJ (2002) Synthesis of lipo-glycopolymer amphiphiles by nitroxide-mediated living free-radical polymerization. J Polym Sci A Polym Chem 40(20) 3379-3391... 

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