Copolymers, graft radical polymerization methods

The advent of controlled radical polymerization methods, such as ATRP, RAFT, and NMP, has allowed for a wide variety of new block and graft polymers to be prepared due to the chemical variety of monomers which can be polymerized by these methods (Matyjaszewski and Tsarevsky, 2009 Matyjaszewski and Braunecker, 2007). Block copolymers can be polymerized by sequential monomer addition, but more often the first block is synthesized, isolated, and... 

Copolymers of VDC can also be prepared by methods other than conventional free-radical polymerization. Copolymers have been formed by irradiation and with various organometaHic and coordination complex catalysts (28,44,50—53). Graft copolymers have also been described (54—58). 

Chung and coworkers have reported on the use of stable borinale or boroxyl radicals (e.g. 114) to mediate radical polymerization." Methacrylates (MMA) and acrylates (trifluoroelhyl acrylate) have been polymerized at ambient temperature to yield polymers with relatively narrow molecular weight distributions.231233 The method has been used to prepare block copolymers and polyolefin graft copolymers.2 4 37... 

In this review, synthesis of block copolymer brushes will be Hmited to the grafting-from method. Hussemann and coworkers [35] were one of the first groups to report copolymer brushes. They prepared the brushes on siUcate substrates using surface-initiated TEMPO-mediated radical polymerization. However, the copolymer brushes were not diblock copolymer brushes in a strict definition. The first block was PS, while the second block was a 1 1 random copolymer of styrene/MMA. Another early report was that of Maty-jaszewski and coworkers [36] who reported the synthesis of poly(styrene-h-ferf-butyl acrylate) brushes by atom transfer radical polymerization (ATRP). 

On the other hand, the PMMA-g-EPR graft copolymers using the FRP method with AIBN showed a different morphology and thermal property from those after using the ATRP method, leading to the fact that the ATRP method is preferable compared to FRP method for the purpose of preparing well-defined macromolecular structures. Poly(EPR) can also be prepared by the free radical polymerization with AIBN [107]. 

Several graft copolymers were prepared based on the anionic polymerization method to overcome some of the major problems encountered in radical-initiated grafting. This method is used to prepare a living synthetic polymer with mono- or dicarbanions to react with modified cellulosic substrates under homogeneous conditions. For example, polyacrylonitrile carbanion was prepared to react with cellulose acetate to generate a cellulose acetate-polyacrylonitrile graft polymer [142]. 

Summary Graft copolymers with poly(organosiloxane) backbone and thermoplastic side chains have been synthesized via the "grafting fi om" method based on azo- and triazene modified poly(organosiloxane)s. Initiation of free radical polymerization is possible from the polymeric azo and triazene initiators after thermal decomposition of the labile frmctions in solution. The graft products have been characterized by NMR, GPC, and DSC. Stable, free standing films can be cast from the graft copolymers. 

Since the 1960 s many researchers have been concerned with the development of feasible and industrially useful methods for the synthesis of cellulose graft copolymers3, 4. Recent investigations have shown that the most efficient approach to this problem involves free radical polymerization initiated by redox systems5. An impressive example is the industrial production of mtilon (cellulose-polyacrylonitrile graft copolymer) and other fibers, particularly those with ion-exchange and acid-resistant properties6"8. ... 

Controlled free-radical polymerization (CFRP) has been used successfully to produce block, graft, and other controlled architecture copolymers within the last decade for a variety of free radically polymerizable monomers. The main techniques include reversible addition fragmentation and transfer (RAFT) polymerization, stable free-radical polymerization (SFRP) mediated by nitroxide/alkoxyamine based radicals, atom transfer radical polymerization (ATRP), diphenyl ethylene (DPE) mediated polymerization, and novel precipitation/emulsion polymerization based methods like free-radical retrograde precipitation polymerization (FRRPP). ... 

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