Dendrimers macroinitiators

Dendrimers as macroinitiators for anionic ring-opening polymerization. Polmyeriza-tion of e-caprolactonc. [I. Gitsov, P. T. Ivanova, J. M. J. Frechet, Macromol. Rapid Commun. 1994,15(5), 387-393] [ 391],... 

Polystyrene B-114401 and poly(acrylate) B-115402 are connected to a dendrimer at its focal core. These are prepared with dendrimer-type macroinitiators with a benzyl bromide at the focal point, from which are initiated the copper-catalyzed living radical polymerizations of styrene and acrylates, respectively. For B-114, various functional groups (R) were introduced into the periphery. 

Scheme 30. 0-th generation carbosilane dendrimer used as a macroinitiator for the ATRP of MMA [256]... 

Yuan et al. [165] reported the synthesis of well-defined dendrimer-star, block-comb polymers by the combination of living ring-opening polymerization and atom transfer radical polymerization on the basis of a dendrimer polyester. Star-shaped dendrimer PCLs were synthesized by the bulk polymerization of e-caprolactone with a dendrimer initiator. The dendrimer PCLs tiien were converted into macroinitiators via esterification with 2-bromopropionyl bromide. And the star-block copolymer dendrimer poly(s-caprolactone)-block-poly(2-hydroxyethyl... 

Various types of block copolymers such as ABA triblock [93,94,105,108], ABC triblock [109-111], PNIPAM-dendrimer [112], and PNIPAM-[star-shaped (or hyperbranched) polymer] [65], and PNIPAM-polyrotaxane-PNIPAM [66] have also been designed/synthesized. For example, Armes et al. have synthesized biocompatible, thermoresponsive ABC and ABA triblock copolymers such as PPO-PMPC-PNIPAM via ATRP using a PPO-based macroinitiator. McCormick et al. have reported the RAFT synthesis of thermally responsive ABC triblock copolymers incorporating M-acryl-oxysuccinimide for facile in situ formation of micelles with cross-linked shells. 

Similar structures can also be prepared using ATRP chemistry and in this case the initiating group is simply a chloromethyl or bromomethyl species at a focal point [204], Linear poly (acrylate) and poly (acrylic acid) blocks [205,206] are then connected to the dendrimer at its core. They were prepared by the copper-catalyzed living radical polymerizations of acrylates with dendrimer-type macroinitiators having a benzyl bromide at the focal point. After hydrolysis, amphiphilic block copolymers with a linear PAA hydrophilic block and a dendritic poly (benzyl ether) as hydrophobic block were obtained [205,206]. 

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