Grafting through approach

This method permits preparation of hybrid materials using macromonomers that can be inorganic, natural products, or other polymers, either prepared by CRP or any other polymerization technique. The grafting density and number of grafted chains depend on the ratio of the concentrations of monomer and macromonomer 

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The grafting through approach involves copolymerization of macromonomers. NMP, ATRP and RAFT have each been used in this context. The polymerizations are subject to the same constraints as conventional radical polymerizations that involve macromonomers (Section 7.6.5). However, living radical copolymerization offers greater product uniformity and the possibility of blocks, gradients and other architectures. 

Conventional fiee radical polymerization of macromonomers remains the most widelyused grafting through approach due to its facile implementation and the great tolerance of the radical process toward many chemically artive and functional groups. The successftil preparation of molecular bmshes via... 

The grafting through approach is typically associated with the copolymerization of macromonomers (polymers with... 

The other example of brush copolymers is based on the grafting through approach where macromonomers with vinyl terminal are synthesized rst and polymerization is carried out through the terminal double bonds to produce densely grafted macromolecules. The grafting through approach in combination with ATRP has also been applied in the copolymerization of PMMA macromonomers with n-butyl acrylate (Roos et al., 1999,2000). 

Figure 6.1 Graft-through approach to micellar nanoparticles via ROMP (M = Ru or Mo catalyst) and chemical structures of the most popular catalysts employed for ROMP.

The third route follows the grafting-through approach in which various protein reactive groups are incorporated within a growing polymer chain by using monomers that can react either directly or after polymerization via the introduced reactive moieties with peptides or proteins [69], Noteworthy, this third approach does not necessarily result only in conjugation of one protein/peptide to a polymer chain, but also in conjugation of several protein/peptide to a polymer chain. 

Grafting occurs through one of three pathways. (1) A preformed polymer is attached to another polymer s side chain in a grafting to approach, (2) a macromonomer bearing a polymeric side chain is polymerized in a grafting through approach, or (3) a polymeric backbone has side chains functionalized with a catalyst or other polymerization initiator from which polymerization occurs in a grafting from approach. 

Figure 22 A brush polymer formed via the grafting through approach. Reproduced with permission from Le, D. Montembault, V. Soutif, J. etal. Macromolecules20 0, 43, 5611. ...

In order to utilize the grafting-through approach, the substrate first needs to be modified with a polymerizable monomer unit, thus becoming a hybrid macromonomer. The macromonomer is then copolymerized with low molecular weight monomers to form a polymer chain with sewed substrate moieties. This method is illustrated in Scheme 7. 

Scheme 7 Grafting-through approach for introduction of polymer brushes to the surface of nanoparticles using ATRP...

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