Reversible addition-fragmentation chain transfer star synthesis

Reversible addition-fragmentation chain transfer (RAFT) polymerization has proven to be a powerful tool for the synthesis of polymers with predetermined molecular weight and low polydispersity [11, 12], In recent years, synthesis of polymers with complex molecular architecture, e.g. block and star copolymers, via the RAFT process have been reported [13],... 

STENZEL-ROSENBAUM M., DAVIS T.P., CHEN V., FANE A.G., Star-polymer synthesis via radical reversible addition-fragmentation chain-transfer polymerization. J. Polym Sci, Part A Polym Chem. (2001), 39 (9), 1353-65. 

The first step for the core-first stars is the synthesis of multifunctional initiators. Since it is difficult to prepare initiators that tolerate the conditions of ionic polymerization, mostly the initiators are designed for controlled radical polymerization. Calixarenes [39, 58-61], sugars (glucose, saccharose, or cyclodextrins) [62-68], and silsesquioxane NPs [28, 69] have been employed as cores for various star polymers. For the growth of the arms, mostly controlled radical polymerizations were used. There are only very rare cases of stars made from nitroxide-mediated radical polymerization (NMRP) [70] or reversible addition-fragmentation chain transfer (RAFT) techniques [71,72], In the RAFT technique one has to differentiate between approaches where the chain transfer agent is attached by its R- or Z-function. ATRP is the most frequently used technique to build various star polymers [27, 28],... 

Stenzel, M.H. Davis, T.P. Star polymer synthesis using trithiocarbonate functional P-cyclodextrin cores (reversible addition-fragmentation chain-transfer polymerization). J. Polym. Sci. A 2002,40 (24), 4498-4512. 

Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization using xanthanes and dithiocarbamates is described [266]. Narrow polydispersities and good control of molecular weight for polymers of M < 30 000 are achieved for these polymers. The living nature of RAFT polymerization allows the synthesis of block copolymers, star polymers and gradient copolymers [266]. 

Reversible addition-fragmentation chain transfer polymerization (RAFT) polymerization of methyl acrylate was combined with cationic polymerization of THF to synthesize comb copolymers. Asymmetric star block copolymers based on polystyrene (PS), PTHF, and PMMA were synthesized by a combination of CROP and redox polymerization methods. Miktoarm star polymers containing poly(THF) and polystyrene arms were also obtained by combining CROP and ATRP methods. Another approach for the synthesis of block copolymers... 

Heteroarm or miktoarm star copolymers have attracted considerable attention in recent years due to the imique properties of these polymers, for example, they exhibit dramatic difference in morphology and solution properties. In comparison with the linear block and star-block copolymers, the s)mthesis of heteroarm or miktoarm star copolymers has been one of the more challenging projects available. A typical example is that the synthesis of the heteroarm H-shaped terpolymers, [(PLLA)(PS)]-PEO-[(PS)(PLLA)], in which PEO acts as a main chain and PS and PLLA as side arms (Fig. 4.11). The copolymers have been successfully prepared via combination of reversible addition-fragmentation transfer (RAFT) polymerization and ring-opening polymerization (ROP) by Han and Pan [166]. Another interesting example is that Pan et al. [167] successfully... 

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