Brushes photoinitiated synthesis

Abstract We review various methods for the photochemical grafting of organic polymers to various substrates including, organic films, membranes, planar gold, silicon wafers, glass, silica gel, silica nanoparticles, and polydimethylsiloxane micro-channels. An emphasis is placed on photoinitiated synthesis of polymer brushes from planar gold and silicon. 

Recently, Dyer used the same strategy to perform a photoinitiated synthesis of a mixed brush by using an AIBN-type initiator boimd to gold [57]. Specifically, they used initiator (24) to modify gold substrates with a binary brush composed of PS and PMMA. As Fig. 11 describes, mixed brushes will respond to the polarity of the solvent. For example, immersion into a non-selective solvent like THF brings both components to the air/hquid interface since PS and PMMA are both soluble in THF. However, immersion into a polar solvent, such as isobutanol, will selectively bring PMMA to the air/hquid interface, while the nonpolar PS collapses into the interior of the film. In contrast, immersion into cyclohexane brings PS to the air/hquid interface and PMMA is driven to the interior. The cycle is completely reversible after immersion into a nonselective solvent like THF. 

Fig. 10 Synthesis of a mixed brush may be accomplished by two strategies (a) A free radical initiator with low efficiency is used. This guarantees that some of the initiator is left after deposition of the first brnsh. Immersion into a second monomer yields a mixed brush where the two polymers are intercalated between each other, (b) A mixed monolayer could be used whereby A and B may be initiated independently (e.g. one is a photoinitiator and the other is a thermal initiator)...

The synthesis of PS core particles by emulsion polymerization and polyelectrolyte brushes by photopolymerization was first reported by Ballauff and co-workers in 1999. Figure 1 displays this route schematically First, nearly monodisperse PS cores are made by conventional emulsion polymerization. Then a thin layer of a suitable photoinitiator is polymerized onto the surface of these cores. The photoinitiator, 2-[p-(2-hydroxy-2-methylpropiophenone)]-ethylene glycol methacrylate... 

Yang, M. Mao, J. Nie, W. Dong, Z. Wang, D. Zhao, Z. Ji, X., Facile Synthesis and Responsive Behavior of PDMS-fc-PEG Dihlock Copolymer Brushes via Photoinitiated Thiol-ene Click Reaction. J. Polym. Sci., Part A Polym. Chem. 2012,50,2075-2083. 

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