Atom transfer radical polymerization ATRP surface initiated

In this review, synthesis of block copolymer brushes will be Hmited to the grafting-from method. Hussemann and coworkers [35] were one of the first groups to report copolymer brushes. They prepared the brushes on siUcate substrates using surface-initiated TEMPO-mediated radical polymerization. However, the copolymer brushes were not diblock copolymer brushes in a strict definition. The first block was PS, while the second block was a 1 1 random copolymer of styrene/MMA. Another early report was that of Maty-jaszewski and coworkers [36] who reported the synthesis of poly(styrene-h-ferf-butyl acrylate) brushes by atom transfer radical polymerization (ATRP). 

SIP-driven polymer brush library fabrication leverages the fact that the polymerization initiation species are permanently bound to the substrate. Since the initiators are tethered, controlled delivery of monomer solution to different areas of the substrate results in a grafted polymer library. In NIST work, initiators bound via chlorosilane SAMs to silicon substrates were suitable for conducting controlled atom transfer radical polymerization (ATRP) [53] and traditional UV free radical polymerization [54, 55]. Suitable monomers are delivered in solution to the surface via microfluidic channels, which enables control over both the monomer solution composition and the time in which the solution is in contact with the initiating groups. After the polymerization is complete, the microchannel is removed from the substrate (or vice versa). This fabrication scheme, termed microchannel confined SIP ([t-SIP), is shown in Fig. 10. In these illustrations, and in the examples discussed below, the microchannels above the substrate are approximately 1 cm wide, 5 cm long, and 300-500 [tm high. 

The need to better control surface-initiated polymerization recently led to the development of controlled radical polymerization techniques. The trick is to keep the concentration of free radicals low in order to decrease the number of side reactions. This is achieved by introducing a dormant species in equilibrium with the active free radical. Important reactions are the living radical polymerization with 2,2,4,4-methylpiperidine N-oxide (TEMPO) [439], reversible addition fragment chain transfer (RAFT) which utilizes so-called iniferters (a word formed from initiator, chain transfer and terminator) [440], and atom transfer radical polymerization (ATRP) [441-443]. The latter forms radicals by added metal complexes as copper halogenides which exhibit reversible reduction-oxidation processes. 

Thermally responsive polymers, such as poly( V-isopropyl acrylamide) (NI-PAm), have also been studied extensively for applications related to those previously discussed [112], De las Heras et al. described the synthesis and patterning of NIPAm brushes on SAMs and their subsequent performance during temperature-dependent adhesion assays of BSA and Streptococcus mutans (Fig. 7). The authors employed p.CP to pattern features of hydrophobic hexadecanethiol and backfilled the surface with an initiator-functionalized alkanethiol. Polymer brushes were grown via surface-initiated atom transfer radical polymerization (ATRP). FITC-BSA was then... 

The patterned organosilane monolayers introducing organolsilane molecule with a polymerization initiating unit are useful as template surfaces for site-specific polymerization. Atom transfer radical polymerization (ATRP) unit was immobilized as a monolayer component. Since ATRP is one of the most successful methods for polymerizing a variety of monomers in a controlled fashion [44, 45], tailor-made surface topography is possible. Several reports have described the formation of polymer thin film by the radical polymerization from the immobilized ATRP initiator [46, 47],... 

The reaction with aryl radicals of this kind has found an interesting application in the direct polymerization of vinylic monomers like styrene, methyl methycrylate (MMA), or hydroxyethyl methacrylate (HEMA) on the diamond. Furthermore, the covalent attachment of an initiator molecule allows for an atom transfer radical polymerization (ATRP) to take place immediately on the diamond surface and results in a covalently bound composite material (Figure 6.41). 

As an illustration of the application of these techniques, the surface of poly(ethylene terephthalate) (PET) films has been modified via the grafting of polyacrylamide (PAM) by surface-initiated atom transfer radical polymerization (ATRP) and UV-initiated grafting in order to obtain a film of PET with a hydrophilic surface [15c],... 

Recently, Liu s group also reported the fabrication of thermoresponsive cross-linked hollow poly(A-isopropylacrylamide) (PNIPAM) nanocapsules with controlled shell thickness via the combination of surface-initiated atom transfer radical polymerization (ATRP) and click cross-linking. Cross-linked PNIPAM nanocapsules were fabricated by the click cross-linking of PNIPAM shell layer with a tri-functional molecule, l,l,l-fm(4-(2-propynyloxy) phenyl)ethane. Due to the thermo-responsiveness of PNIPAM, cross-linked PNIPAM nanocapsules exhibit thermo-induced collapse/swelling transitions that make it possible to classify them as nanogels. 

Scheme 5.1 CNT-based macroinitiators for surface-initiating atom transfer radical polymerization (ATRP). ...

Fig. 6.39 Modification of a macroporous silicon scaffold with initiator-terminated self-assembled monolayers (a) and then immersed in the atom transfer radical polymerization (ATRP) solution where the surface-initiated copolymerization of sulfopropyl methacrylate (SPM) and monomethoxy oligo-(ethylene glycol) methacrylate (MeOEGMA) was carried out (b). Also depicted are the chemical structures of the copolymer bmsh (n = 0.87, m = 0.13, x = 5) and the surface-confined ATRP initiator (Reproduced from [494] with permission)...

Lately, surface-initiated atom transfer radical polymerization (ATRP) has been used to obtain a surface-grafted membrane (Liu et al. 2010). A porous PTFE membrane was treated by the hydrogen plasma and the C-F groups of the modified surface became effective initiators of ATRP. PEG methacrylate or its copolymer with A-isopropylacrylamide was grafted in such a way and the modified membranes showed temperature-responsive and protein repulsion features (Liu et al. 2010). 

In recent years, focus has moved to the use of living radical polymerization techniques such as atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) for the production of well-defined polymer coatings. Both the grafting from and grafting to approaches have been explored for the attachment of MPC-based polymers onto a variety of substrates. Grafting from requires the incorporation of initiator sites onto the biomaterial surface prior to the polymerization reaction. This usually involves a series of... 

Luo et al. [6] used a polydimethylsiloxane macro-initiator to initiate polymerization of methacrylate monomers with fluorinated side groups to prepare fluorosilicone polymers. To obtain diblock copolymers with a low surface energy, they designed poly(dimethylsiloxane)-block-poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) (PDMS-1 -PHFBMA) diblock copolymers by atom transfer radical polymerization (ATRP) technique. To initiate 2,2,3,3,4,4, 4-heptafluorobutyl methacrylate polymerization, bromine end-capped polydimethylsiloxane (PDMS-Br) was used as the macro-initiator. Scheme 6.5 shows a schematic representation of the PDMS-fc-PHFBMA diblock copolymers. The system was strictly deoxygenated... 

Recently, we report an approach for the preparation of polymer brushes on different kinds of PET surfaces (films, fibers and fabrics). The PET surfaces were first reacted with 1,2-diaminoethane by aminolysis reaction to incorporate functional groups on the surface. Then, in a second step, atom transfer radical polymerization (ATRP) initiators were grafted by reaction with bromoisobutyryl bromide. Surface-initiated ATRP was performed in bulk using styrene monomer and the adequate catalytic system in the presence of sacrificial initiator. Polymer brushes were obtained with a good controlled of polymerization (46). 

To overcome these problems, a surface-initialed living radical polymerization technique is used for preparing polymer brush surfaces, where precisely controlled polymer chains are densely tethered. The technique also can be used to construct block copolymer on the surfaces by sequentially grafting another polymer via the active polymer-end groups of a first-grafted polymer brush. As a typical surface-initiated Uving radical polymerization, atom transfer radical polymerization (ATRP) and reversible addition-fragmentafion chain transfer radical (RAFT) polymerization are... 

Matrab, T., J. Chancolon, M. Mayne-L Hermite, J. N. Rouzaud, G. Deniau, J.-P. Boudou, M. M. Chehimi, and M. Delamar. Atom transfer radical polymerization (ATRP) initiated by aryl diazonium salts A new route for surface modification of multiwalled carbon nanotubes by tethered polymer chains. Colloids Surf. A Physicochem. Asp. 287, 2006 217-221. 

Chemical structure of phenyl azide and atom transfer radical polymerization (ATRP) initiator-carrying random copolymer (AIP) and schematic representation for the immobilization of AIP on polymeric substrate followed by surface-initiated ATRP. (From Ohno, K., et al.. Macromolecules, 43,5569-5574,2010.)... 

Dense polymer structures with well-controlled compositions and dimensions are preferentially grown from a wide range of surfaces by atom transfer radical polymerization (ATRP). Different bromo-terminated molecules ranging from silanes, thiols, or disulfides to aromatic moieties derived from diazonium ions " have been proposed to initiate the polymer growth. 

Zhang, F., Xu, F.J., Kang, E.T., Neoh, K.G. 2006. Modification of Titanium via Surface-Initiated Atom Transfer Radical Polymerization (ATRP). 

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