Functional colloids with controlled structure and composition have great potential application in many fields such as diagnose target therapy controlled release catalysis and separation. Their investigation involves materials science medicine science information science energy and environmental science.

A series of results about hierarchical complex composite colloids have been synthesized in State Key Laboratory of Polymer Physics and Chemistry ICCAS. Hollow composite colloids with synchronously tunable shell and cavity size were prepared using core-shell gel colloids as template (Angew. Chem. Int. Ed. 2003 42 1943 - 1945; Adv. Funct. Mater. 2003 13 949 - 954). In order to avoid fracturing the shell during removal of the core template porous hollow polymer colloids were used as templates to synthesize a series of novel colloids with tunable microstructure such as double-shelled hollow colloids and bionic colloids with nanosized protruded pillars (Angew. Chem. Int. Ed. 2005 44 6727 - 6730; Adv. Funct. Mater. 2005 15 1523 - 1528).

Recently this research group has developed a new method to synthesize Janus colloids. The corresponding results have been published in the Journal Angewandte Chemie（Angew. Chem. Int. Ed. 2008 47 3973-3975). Janus colloids refer to such colloids having two parts with different composition and properties integrated. It is challenging to develop efficient synthesis methods. In particular the rotation for the colloids at the Pickering emulsion liquid-liquid interface makes the synthesis more difficult even impossible. The researchers have proposed a new method and realized the biphasic synchronous graft polymerization of both hydrophilic and hydrophobic polymers onto both sizes of the silica colloids at the interface whilst the rotation is further restricted (Fig. 1). As a result composite Janus colloids are achieved (Fig. 2). Some functional nanoparticles are preferentially either adsorbed or in situ reduced at the specific area of these colloids. The Janus performance is verified meanwhile other composite functional Janus colloids are derived.

This work was supported by the National Science Foundation of China and the Chinese Academy of Sciences.

Angew. Chem. Int. Ed （2008 47 3973-3975).

Fig. 1.  Schematic synthesis of Janus colloids.

Fig. 2.  SEM and TEM images of Janus colloids with Au nanoparticles preferentially labeled within the hydrophilic region.