Star polymers, atom transfer radical

Star polymers are a class of polymers with interesting rheological and physical properties. The tetra-functionalized adamantane cores (adamantyls) have been employed as initiators in the atom transfer radical polymerization (ATRP) method applied to styrene and various acrylate monomers (see Fig. 21). 

Figure 21. Atom transfer radical polymerization (ATRP) synthetic route to tetrafunctional initiators of a star polymer with adamantyl (adamantane core). Taken from Ref. [91] with permission.

The synthesis of A2B miktoarm star polymers has been discussed and exemplified using PIB as a component. The synthesis involves a quasi living cationic polymerization of isobutylene from a monofunctional cationic initiator. This initiator also contains a blocked hydroxyl group. Eventually, the blocked hydroxyl group of the initiator is deblocked, and functionalized with a branching agent. This activated reagent is then used for an atom transfer radical polymerization process of /erf-butyl acrylate (18). 

L.K. Breland and R.F. Storey, Polyisobutylene-based miktoarm star polymers via a combination of carbocationic and atom transfer radical polymerizations, Polymer, 49(5) 1154-1163, March 2008. 

Pansier [2] used the bromomethyl analogue, (II), of the Step 2 product in the atom transfer radical polymerization of methyl methacrylate. Lewandowski [3] prepared the tribromomethyl analogue, (111), by reacting with trimethylolpro-pane and then used this reagent to prepare methyl methacrylate star polymers. A reaction profile is provided in Table 3. 

H) Atom transfer radical polymerization Numerous reports have been published regarding the synthesis of star polymers using multifunctional initiators capable of initiating the atom transfer radical polymerization (ATRP) of certain monomers, mainly styrene, methacrylates, and acrylates. The living character of the growing chain ends provides the possibility for the synthesis of star-block copolymers. 

Costa, R. O. R. Vasconcelos, W. L. Tamaki, R. Laine, R. M., Organic/Inor-ganic Nanocomposite Star Polymers via Atom Transfer Radical Pol)uneriza-tion of Methyl Methacrylate Using Octafunctional Silsesquioxane Cores. Macromolecules 2001, 34, 5398-5407. 

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... 

Benedicte Lepoittevin has been an Assistant Professor in Pol)nner Chemistry at the University of Paris-sud (France) since 2002. Prior to this she spent one year at the University of Bordeaux as postdoctoral fellow where she studied the synthesis of star and dendritic polymers using atom transfer radical polynierization. In 2000 she defended a Ph.D thesis at the University of Paris VI on the synthesis cyclic polymers by controlled radical and anionic polymerizations under the supervision of Prof. Patrick Hemery. Her scientific interests include PET surface modification, controlled radical polymerization and polymer synthesis using carbohydrates and essential oils derivatives in order to obtain polymer materials with antibacterial properties. 

Guo, Y.-M., Pan, C.-Y., and Wang, J. (2001). Block and star block copolymers by mechanism transformation. VI. Synthesis and characterization of A4B4 miktoarm star copolymers consisting of polystyrene and polytetrahydrofuran prepared by cationic ring-opening polymerization and atom transfer radical polymerization. J. Polym. Sci., Part A Polym. Chem., 59(13) 2134-2142. 

Durmaz, H., Kaiatas, F., Tunca, U., and Hizal, G. (2(X)6b) Preparation of ABC miktoarm star terpolymer containing polyfethylene glycol), polystyrene, and poly(tert-butylacrylate) arms by combining Diels-Alder reaction, atom transfer radical, and stable free radical polymerization routes. Journal of Polymer Science Part A-Polymer Chemistry, 44,499. 

Abraham, S., Ha, C.-S., and Kim, I. (2006) Self-assembly of star-shaped polystyrene-WocA -polypeptide copolymers synthesized by the combination of atom transfer radical polymerization and ring-opening living polymerization of a-amino acid-N-carboxyanhydrides. Journal of Polymer Science Part A Polymer Chemistry,... 

Reversible deactivated radical polymerization processes, which have been referred to as living/controlled radical polymerizations, allow for producing polymeric materials with controlled molecular masses, low dispersities, and complex maaomolecular architectures, such as block and comb-like copolymers as well as star-shaped (co)polymers. In addition to nitroxide-mediated polymerization (NMP) ° and atom-transfer radical polymerization (ATRP), ° reversible addition fragmentation chain-transfer (RAFT) polymerization is an attractive new method. " ... 

Han D, Tong X, Zhao Y (2012) Synthesis and characterization of six-arm star polystyrene-block-poly(3-hexylthiophene) copolymer by combination of atom transfer radical polymerization and click reaction. J Polym Sci A Polym Chem 50 4198-4205... 

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