Nitroxide-mediated radical grafting

There are a number of other reactions that can be used cycloaddition of an azide group allowed binding of polystyrene [43], while a radical coupling was exploited to graft polymers prepared by a nitroxide-mediated radical polymerization [121]. Other end groups could be used it was shown above how amide bonds were utilized to attach water-soluble polymers amino or hydroxyl moieties are other conventional groups. 

Nitroxide-mediated Radical Polymerization (NMRP) Approach to Polymer-grafted CNTs... 

With the development of controlled radical polymerization techniques like nitroxide-mediated radical polymerization (NMRP), atom transfer radical polymerization (ATRP), and reversible addition fragmentation chain transfer (RAFT) polymerization (see Section 3.2), the field of linear glycopolymers has significantly flourished, especially as control of molar mass and monomer sequence has become available, even for functionalized monomers. This enables incorporation of new and more complex glycomonomers as well as allows controlled dispersity, end group functionality, and monomer sequences in block, star-shaped, and graft copolymers, and eventually... 

Matsuno R, Otsuka H, Takahara A (2006) Polystyrene-grafted titanium oxide nanoparticles prepared through surface-initiated nitroxide-mediated radical polymerization and their application to polymer hybrid thin films. Soft Matter 2(5) 415... 

Jo TS, Yang M, BrowneU LV, Bae C. Synthesis of quaternary ammonium ion-grafted polyolefins via activation of inert C—H bonds and nitroxide mediated radical polymerization. J Polym Sd A Polym Chem. 2009 47 4519-4531. 

Dynamic formation of graft polymers was synthesized by means of the radical crossover reaction of alkoxyamines by using the complementarity between nitroxide radical and styryl radical (Fig. 8.13) [40]. Copolymer 48 having alkoxyamine units on its side chain was synthesized via atom transfer radical polymerization (ATRP) of TEMPO-based alkoxyamine monomer 47 and MMA at 50°C (Scheme 8.9). The TEMPO-based alkoxyamine-terminated polystyrene 49 was prepared through the conventional nitroxide-mediated free radical polymerization (NMP) procedure [5,41], The mixture of copolymers 48 and 49 was heated in anisole... 

For styrene-based random copolymers, functional groups can be introduced into the polymer chains via copolymerization with functional styrene derivatives, because the electronic effects of the substituents are small in the metal-catalyzed polymerizations in comparison to the ionic counterparts. Random copolymer R-6 is of this category, synthesized from styrene and />acetoxystyrene.372 It can be transformed into styrene// -vinylphenol copolymers by hydrolysis.380 The benzyl acetate and the benzyl ether groups randomly distributed in R-7 and R-8 were transformed into benzyl bromide, which can initiate the controlled radical polymerizations of styrene in the presence of copper catalysts to give graft copolymers.209 Epoxy groups can be introduced, as in R-9, by the copper-catalyzed copolymerizations without loss of epoxy functions, while the nitroxide-mediated systems suffer from side reactions due to the high-temperature reaction.317... 

The metal-catalyzed copolymerization from carbon-halogen bonds in the main chain can be employed widely for graft polymer synthesis. A combination of nitroxide-mediated and copper-catalyzed living radical polymerizations, for example, gives graft copolymers G-6, where the main chain is prepared by the former.432 The chlorobenzyl unit in the copolymer is not active during the polymerization but, upon copper catalysis, it can initiate living radical polymerizations of styrene and methacrylates. 

Li J, Chen XR, Chang YC. Preparation of end-grafted polymer brushes by nitroxide-mediated free radical polymerization of vaporized vinyl monomers. Langmuir 2005 21 (21) 9562-7. 

Initiators for the controlled living radical polymerization could also be introduced to silica particles. Nitroxide-mediated polymerization (NMP) conducted with styrene in miniemulsion led to the generation of core-shell particles, with styrene grafted to the central silica particle [131]. PBA could be polymerized from 20 nm silica beads by attaching an ATRP agent to the silica surface and subsequent miniemulsion polymerization [132]. Confining the polymerization to miniemulsion droplets could avoid gel formation, which was observed in the bulk reaction. Due to the limited monomer diffusion, only 25-35% of conversion could be obtained in bulk. 

X-ray diffractograms of filler before grafting (I) and filler after grafting using conventional free radical polymerization (II) and nitroxide-mediated living polymerization (III). (Reproduced from Mittal, V., /. Colloid Interface Sci., 314,141, 2007.)... 

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