Iniferter approach

Surface modification can be achieved by the surface derivatization of functional-group-bearing low-molecular-weight substances, the grafting of polymer to and from the surface and amphiphilic polymer coating. The main theme of this article is focused on initiator-transfer-terminator (iniferter)-based grafting-from-surface and derivatization-on-surface approaches aiming at precision surface architectures, which are primary determinants of the biocompatibility of medical devices. 

In a contribution published in 2005 the group of Sellergren compared the performance of composite MIPs imprinted with propazine and prepared from the same porous silica support using the pore-filling technique (with and without final removal of the silica) as well as the layer grafting approach with an immobilised iniferter [148], The MIP composite prepared by layer grafting was found to exhibit the best performance when employed as stationary phase in HPLC, although extensive optimisation of the imprinted layer thickness was required. 

Byme et al. [124] have shown the possibility of creating imprinted polymer ordered micropattems, of a variety of shapes and dimensions, on polymer and silicon substrates using iniferters and photopolymerization. They applied this approach to the recognition of D-glucose using copolymer networks containing poly(ethylene glycol) and functional monomers such as acrylic acid, 2-hydro-xyethyl methacrylate, and acrylamide. 

The free radical polymerization of styrene initialized by iniferter is influenced by chemical binding of iniferter on the surface of the silica." This reaction is used for grafting the polymer onto the surface of the silica. A similar approach is used when carbon whisker is incorporated during the graft-polymerization of methyl methacrylate. Depending on how the whisker is prepared, surface conversion can be increased up to twelve times compared to a polymerization with no whisker present. The addition of graphite to the poly esterification reaction doubles the molecular weight of the polymer. ... 

MIPs can be synthesized in the pores and on the surface of pre-made porous particles. Porous silica particles have been applied for this purpose. To ensure that the imprinted polymer is attached firmly to the particle, the particles are often chemically modified by coupling of polymerizable groups or initiator molecules to the particle surface prior to the MIP polymerization [100-102]. The use of immobilized initiators is often referred to as the iniferter (initiator-transfer agent-terminator) approach [103]. The method has been applied to the imprinting of a range of templates [104—107]. 

Since termination and chain transfer are still present in iniferter-assisted photopoiymerizations, these systems are sometimes described as controlled, rather than living, free-radical polymerizations. Regardless, this approach enables control of bulk free-radical photopol5unerizations that is not otherwise... 

Preformed silica particles have been used as supports to which imprinted layers have been grafted. In earlier approaches, polymerizable nnits were attached to the silica support followed by grafting to polymerization using template, functional monomer, cross-linker and soluble initiator. " It is now more common to attach initiator or iniferter units to the silica snpport, allowing for a grafting from approach. The template molecule may also... 

As stated previously, the iniferter method is not suitable for aU monomers. Therefore, the application of a single mode polymerization technique for the synthesis of block copolymers is severely limited, and suffers from the requirement for care in the order of monomer addition. In order to extend the range of monomers for the synthesis of block copolymers, a mechanistic transformation approach was proposed, by which the polymerization... 

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