Poly nitroxide mediated polymerization

During the last 5 years, there have been several reports of multiblock copolymer brushes by the grafting-from method. The most common substrates are gold and silicon oxide layers but there have been reports of diblock brush formation on clay surfaces [37] and silicon-hydride surfaces [38]. Most of the newer reports have utilized ATRP [34,38-43] but there have been a couple of reports that utilized anionic polymerization [44, 45]. Zhao and co-workers [21,22] have used a combination of ATRP and nitroxide-mediated polymerization to prepare mixed poly(methyl methacrylate) (PMMA)Zpolystyrene (PS) brushes from a difunctional initiator. These Y-shaped brushes could be considered block copolymers that are surface immobilized at the block junction. 

Controlled/ Living radical polymerization (CRP) of vinyl acetate (VAc) via nitroxide-mediated polymerization (NMP), organocobalt-mediated polymerization, iodine degenerative transfer polymerization (DT), reversible radical addition-fragmentation chain transfer polymerization (RAFT), and atom transfer radical polymerization (ATRP) is summarized and compared with the ATRP of VAc catalyzed by copper halide/2,2 6 ,2 -terpyridine. The new copper catalyst provides the first example of ATRP of VAc with clear mechanism and the facile synthesis of poly(vinyl acetate) and its block copolymers. 

VAc has been successfully polymerized via controlled/ living radical polymerization techniques including nitroxide-mediated polymerization, organometallic-mediated polymerization, iodine-degenerative transfer polymerization, reversible radical addition-fragmentation chain transfer polymerization, and atom transfer radical polymerization. These methods can be used to prepare well-defined various polymer architectures based on PVAc and poly(vinyl alcohol). The copper halide/t is an active ATRP catalyst for VAc, providing a facile synthesis of PVAc and its block copolymers. Further developments of this catalyst will be the improvements of catalytic efficiency and polymerization control. 

Post-polymerization functionalization has also been applied to the synthesis of terpyridine-modified polymers [ 126]. In a recent approach, Schubert and colleagues employed this method to prepare poly(pentafluorostyrene) with terpyridines in the side chains [127]. First, poly(pentafluorostyrene) with a narrow polydispersity index of just 1.08 was synthesized by nitroxide-mediated polymerization. In a second step, this polymer was converted with amine-functionalized terpyridine under microwave heating, selectively substituting the para-fluorines. Addition of iron(II) sulfate to a solution of the terpyridine-functionalized polymer in a mixture of chloroform and methanol leads to gelation at a polymer concentration of 33 g In another work, Schubert and coworkers prepared metal-cross-Iinked polymer networks from linear and tri-arm PEG precursors, both functionalized with terpyridine at their OH-termini [128]. Quantitative functionalization of these precursors was achieved by conversion of the hydroxy-functionalized PEG derivatives with 4-chloro-2,2 6, 2"-terpyridine under basic conditions. However, quantitative cross-linking with iron(II) chloride was not observed in methanol solutions, neither at room temperature nor at elevated temperature, but only a small quantity of cross-linked material precipitated from the solution. This observation was attributed to a strong tendency of the tri-arm PEG to form intramolecular complexes, acting as a chain stopper rather than as a cross-linker. 

They can be synthesized either by block copolymerization of monomers having acceptor pendant units or by synthesis of BCP precursors at first stage, followed by chemical grafting at later stage to incorporate the pendant acceptor units. For example, poly(bisphenyl-4-vinylphenylamine)-fo/ocfc-poly(perylene diimide acrylate) (PvTPA-h-PPerAcr, PI), poly(bis(4-methoxyphenyl)-4 -vinylphenylamine)-b/ocA -poly(perylene diimide acrylate) (PvDMTPA-it-PPerAcr, P2), and poly(N,N-bis(4-methoxyphenyl)-N-phenyl-N -4-vinylphenyl-(l,l -biphenyl)-4,4 -diamine)-b/ock-poly(perylene diimide acrylate) (PvDMTPD-h-PPerAcr, P3) were prepared by nitroxide-mediated polymerization (NMP) using monomer having acceptor pendant rmits [229,282,302]. 

E. Kaul, V. Senkovskyy, R. Tkachov, V. Bocharova, H. Komber, M. Stamm, A. Kiriy, Synthesis of a Bifunctional Initiator for Controlled Kumada Catalyst- Transfer Polycondensation/Nitroxide-Mediated Polymerization and Preparation of Poly(3-Hexylthiophene)-Polystyrene Block Copolymer Therefrom. Macromolecules 2010,43,77-81. 

Well-defined amphiphilic block copolymers can be prepared by various controlled polymerization reactions, such as atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT), and nitroxide mediated polymerization (NMP). The amphiphilic copolymers most frequently used in bio-inspired strategies consist of hydrophilic blocks, such as poly(aciylic acid) (PAA), poly(ethylene oxide) (PEO), or poly(2-methyl oxazoline) (PMOXA), and a hydrophobic block, such as... 

Rager, T., Meyer, W.H. and Wegner, G. (1999) Micelle formation of PAA-PMMA block copolymers in mixtures of water with organic solvents. Macromol. Chem. Phys., 200,1672-1680. LarueUe, G., Pran9ois, J. and Billon, L. (2004) Self-assembly in water of poly(acrylic acid) based diblock copolymers synthesized by nitroxide-mediated polymerization. Macromol. Rapid Commun., 25,1839-1844. 

Similarly to the poly(acrylamide)s and poly(vinyl amide)s, POEGMA can be prepared by free radical polymerization, CRP and anionic polymerization, whereby the latter two methods result in well-defined polymer structures with defined end-groups. Even though CRP of OEGMA can be performed by ATRP and RAFT polymerization (Becer et al, 2008 Lutz and Hoth, 2006a), the methacrylate obstructs OEGMA homopolymeriza-tion by nitroxide mediated polymerization. This can, however, be overcome by copolymerization with a minor amount of styrenic comonomer that enables good control over the polymerization (Charleux et al., 2005 Lessard et al., 2012). 

Schulte, T., Siegenthaler, K.O., Luftmann, H. et al. (2005) Nitroxide-mediated polymerization of N-isopropylacry-lamide Electrospray ionization mass spectrometry, matrix-assisted laser desorption ionization mass spectrometry, and multiple-angle laser light scattering studies on nitroxide-terminated poly-N-isopropylacrylamides. Macromolecules, 38,6833-6840. 

RAFT polymerization or nitroxide-mediated polymerization (NMP) was used instead of ATRP for the synthesis of the block copolymer of polythiophene and polyisoprene or polystyrene, because ATRP generates materials containing traces of metals from the catalyst [146]. A block copolymer of P3HT and poly (perylene bisimide acrylate) was also synthesized by NMP from a polythiophene macroinitiator (Scheme 51) [147, 148]. This block copolymer is a crystalline-crystalline donor-acceptor block copolymer and shows microphase separation, implying efficient photovoltaic applications. A similar polythiophene macroinitiator for NMP was used for the synthesis of fullerene-grafted rod-coil block copolymers [149]. 

Scheme 51 Synthesis of block copolymer of P3HT and poly(perylene bisimide acrylate) by nitroxide-mediated polymerization from polythiophene macroinitiator...

Qiao XG, Fansalot M, Bourgeat-Lami E, Charleux B (2013) Nitroxide-mediated polymerization-induced self-assembly of poly(poly(ethylene oxide) methyl ether methacrylate-co-styrene)-h-poly(n-butyl methacrylate-co-styrene) amphiphilic block copolymers. Macromolecules 46 4285 295... 

---