Poly nitroxide mediated radical

Fig. 27 Continuous flow microreactor system for nitroxide-mediated radical polymerization (NMP) of poly(styrene) or poly(n-butyl acrylate). R microtube reactor...

There are fewer reports on the preparation of block copolymers via the combination of anionic polymerization with nitroxide-mediated syntheses [132,133]. As shown in Scheme 3.30, the reaction product of sodium with 4-hydroxyl-TEMPO initiated the anionic polymerization of ethylene oxide at 60 °C in THF solution. After treatment with methanol, TEMPO-terminated PEO was obtained, and then used in the nitroxide-mediated radical polymerization of St at 120 °C resulting in block copolymers of type CLB-17 [133]. Another method is the transformation of anionic polymerization into nitroxide-mediated radical polymerization. A poly(butadienyl)lithium solution in... 

Santerre, J. P., K. Woodhouse, G. Laroche, and R. S. Labow 2005. Understanding the biodegradation of polyurethanes From classical implants to tissue engineering materials. Biomaterials. 26 7457-70. Sawhney, A. S., C. P. Pathak, and J. A. Hubbell 1993. Bioerodible hydrogels based on photopolymerized poly(ethyleneglycol)-co-poly(alpha-hydroxyacid) diacrylate macromers.Macromo/ec /es. 26 581-87. Sciannamea, V., R. Jerome, and C. Detrembleur 2008. In-situ nitroxide-mediated radical polymerization (NMP) processes Their understanding and optimization. Chemical Reviews. 108 1104-26. 

Another prime advantage of living free radical procedures is the compatibility of both nitroxide-mediated and ATRP procedures with functionalized monomers. An excellent example of this is the preparation of poly(2-hydroxyethyl methacrylate) with controlled molecular weight and low polydispersity by the ATRP of HEMA (Scheme 13) [40]. In contrast to normal monomers the... 

Recently, living radical polymerizations have been well developed, and various methods such as (1) iniferter mediated radical polymerization [31], (2) transition metal-mediated radical polymerization or atom transfer radical polymerization (ATRP) [32-34] (3) nitroxide-mediated free-radical poly-... 

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]. 

Since the nitroxide and the carbon-centered radical diffuse away from each other, termination by combination or disproportionation of two carbon-centered radicals cannot be excluded. This will lead to the formation of dead polymer chains and an excess of free nitroxide. The build-up of free nitroxide is referred to as the Persistent Radical Effect [207] and slows down the polymerization, since it will favor trapping (radical-radical coupling) over propagation. Besides termination, other side reactions play an important role in nitroxide-mediated CRP. One of the important side reactions is the decomposition of dormant chains [208], yielding polymer chains with an unsaturated end-group and a hydroxyamine, TH (Scheme 3, reaction 6). Another side reaction is thermal self-initiation [209], which is observed in styrene polymerizations at high temperatures. Here two styrene monomers can form a dimer, which, after reaction with another styrene monomer, results in the formation of two radicals (Scheme 3, reaction 7). This additional radical flux can compensate for the loss of radicals due to irreversible termination and allows the poly-... 

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. 

Stalmach et al. proceeded to the synthesis of a diblock copolymer, comprised of an oligo-PV rod and a poly(n-butyl acrylate) flexible segment, using the macroinitiator procedure. Nitroxide-mediated controlled radical polymerization (NMCRP) using the macroinitiator 11 was performed in order to control the length of the coil blocks. 

However, all synthetic approaches involving ATRP rely on a metal catalyst. Full metal-free and thus greener approaches to block copolymers were realized by the combination of Upase ROP with nitroxide-mediated living free radical polymerization [44]. With this system it was also possible to successfully perform a one-pot chemoenzymatic cascade polymerization from a mixture containing a dual initiator, CL and styrene (Fig. 12). Moreover, it was shown that this approach is compatible with the stereoselective polymerization of 4-methylcaprolactone for the synthesis of chiral block copolymers. A metal-free synthesis of block copolymers using a radical chain transfer agent as a dual initiator in enzymatic ROP to yield poly(CL-f -styrene) was also reported recently [119]. 

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... 

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