ABSTRACT
However, grafting from initiator-containing self-assembled monolayers (SAMs) is more attractive, since a high density of initiators is immobilized on the surface and the initiation mechanism is more well-defined [4]. Apart from the monolayers prepared by the Langmuir-Blodgett method, much of the work on SAMs has involved thiols on gold surface and silanes on oxidized silicon surface [6]. These SAMs are chemically less robust. Monolayers of thiols on gold can be easily removed when heated in a solvent [7]. Organosilane monolayers exhibit good stability. However, the silicon-oxygen bonds are susceptible to hydrolysis and are labile in hydrofluoric acid [8]. Recently, a number of reports on the direct covalent attachment of organic monolayers to the oriented single crystal silicon surface in the absence of the native oxide layer have appeared [9-13]. Previous studies have shown that an alkyl monolayer can be tethered covalently to the hydrogen-terminated Si(100) and Si(l 11) surfaces via the use of a radical initiator or a metal complex catalyst, as well as via thermal activation, photoirradiation, or electrochemical reaction [14],
On the other hand, progress in polymerization has made it possible to produce polymer brushes on solid surfaces with controllable lengths. Recently, most of the studies have been centered on the synthesis of well-defined polymer brushes by living radical polymerization. The technique combines the virtues of living polymerization with the versatility and convenience of free-radical polymerization [15-18]. Successful examples of the living radical polymerization include nitroxide-mediated radical polymerization [19], atom transfer radical polymerization (ATRP) [20, 21] and reversible addition-fragmentation chain transfer (RAFT) polymerization [22].
