Copolymer dendrigraft

Schappacher, M., Putaux, J.L., Lefebvre, C., and Deffieux, A. (2005b) Molecular containers based on amphiphiUc PS-h-PMVE dendrigraft copolymers Topology, organization, and aqueous solution jaoperties. Journal of the... 

DENDRIGRAFT (ARBORESCENT)-POLY(STYRENE)-GRAFT-POLY(ISOPRENE) COPOLYMERS... 

Characterization data for dendrigraft-po y(styr ene)-graft-po y(tert-buty methacrylate) copolymers synthesized with either short (Mw 5000, PtBMA5) or long (Mw 30000, PtBMA30) branches are provided in Table 9.7. The low apparent polydispersities (MJMn = 1.13-1.20) obtained for the graft polymers are indicative of a narrow molecular size distribution. 

Frechet and coworkers recently described how living free radical polymerization can be used to make dendrigrafts. Either 2,2,6,6-tetramethylpiperidine oxide (TEMPO) modified polymerization or atom transfer radical polymerization (ATRP) can be used [96] (see Scheme 10). The method requires two alternating steps. In each polymerization step a copolymer is formed that contains some benzyl chloride functionality introduced by copolymerization with a small amount of p-(4-chloromethylbenzyloxymethyl) styrene. This unit is transformed into a TEMPO derivative. The TEMPO derivative initiates the polymerization of the next generation monomer or comonomer mixture. Alternatively, the chloromethyl groups on the polymer initiate an ATRP polymerization in the presence of CulCl or CuICl-4,4T dipyridyl complex. This was shown to be the case for styrene and n-butylmethacrylate. SEC shows clearly the increase in molecu-... 

The graft copolymers with poly (H-1) arms have multiple carbon—halogen bonds that can initiate copper-catalyzed radical polymerization to give highly branched dendrigraft polymers.432 The products with styrene or nBMA had relatively narrow MWDs because each chain was prepared by living polymerization. 

An approach similar to the previous divergent grafting-from method also served to synthesize dendrigraft poly(L-lysine) by ring-opening polymerization [111], styrene homopolymers and styrene-methacrylate copolymers by a combination of stable free-radical polymerization and atom transfer radical polymerization (ATRP) [112], and copolymers of 2-hydroxyethyl methacrylate with styrene or ferf-butyl methacrylate by ATRP [113]. 

Considering the versatility of dendrigraft polymer syntheses, it is relatively easy to introduce features in the molecules of interest for specific applications. Since the chain segments of dendrigraft polymers are covalently bonded, copolymers with amphiphilic character behave like unimolecular micelles that provide an interesting basis for comparison with regular micelles. The self-assembly of... 

Synthesis of dendrigrafts of citric acid on acrylonitrile/acrylic acid copolymer solid films via repetitive DCC-induced esterification reaction were reported by Kish et al. Since after each coupling cycle the unreacted sites cannot be distinguished from the carboxylic ends of the units that had just been attached, it is likely that a range of dendrons of different generations (rather than monodispersed dendrons of a certain generation) populate the surface of the film. 

Figure 6.4 Schematic representation of (a) core-shell morphology and (b) temperature-responsive supramolecular self-assembly of arborescent PS-gro/i-P2VP5 copolymers in toluene. (Reprinted with permission from S.I. Yun, G.E. Gadd, V. Lo et al, Temperature-responsive supramolecular assembly of dendrigraft micelles with a solvophilic core -solvophobic shell structure, Macromolecules, 41, 7166-7172. 2008 American Chemical Society.) (Colour version of this figure is available on the book companion web site.)...

---