Bumjoon J. Kim

A Strategy to Decorate the Surface of NPs and Control their Locations within Block Copolymer Templates

Polymer nanocomposites consisting of polymers and inorganic nanoparticles (NPs) have attracted many attentions due to their promising potentialsof diverse applications such as solar cell, sensors, catalysts, ferroelectric devices, etc. To impart sufficient stability of NPs and integrate NPs into polymer matrix, it is a prerequisite that the surface of the NPs is properly treated with various ligands having desired properties. Up to date, a number of strategies to synthesize the appropriate gold nanoparticles (Au NPs) have been reported. The most popular method that has been for a long time to prepare Au NPsis to use citrate reduction of HAuCl4 in water, which was introduced by Turkevitch (Turkevich et al., 1951). And this method was developed by Frens to obtain controlled size of Au NPs from 10 to 100 nm, via varying the concentration ratio between HAuCl4 and sodium citrate (Frens, 1973). In organic solvent, the so called “two-phase method” developed by Brust et al. has a considerable impact in this field until today due to the facile synthesis of stable Au NPsthat are protected by alkanethiols with controlled size and monodispersity (Brust et al., 1994). Later, they also introduced the “one-phase method” in methanol (Brust et al., 1995) and Yee et al. have expanded this method to various metal NPs such as gold, palladium and iridium in tetrahydrofuran (Yee et al., 1999). Furthermore, Hostetler et al. demonstrated that the functionality of monolayer protected NPs can be further enhanced via ligand exchange method (Hostetler et al., 1999). Recently, the inorganic NPs which is surface modified with polymeric ligands instead of the small surfactant molecules, such as alkanethiols or citrate, have attracted great interest as they can provide not only the improved stability but also various functionalities, unique structure and characteristics, and compatibility with other matrices. As a versatile approach for the surface modification of NPs, it has been shown that various polymers can be grafted onto the NP surface via “grafting-from”, “grafting-to”, “ligand exchange” or “templating” methods. In the “grafting-from” method, polymers are usually grown from the NP surfacesvia living-free radical polymerization, which are modified with the initiators. In contrast, when the end-functionalized polymers are synthesized, such as thiol-terminated