Assembly of oppositely charged microgels at the air/water interface.

We present an assembly of cationic and anionic microgels at the air/water interface. Monodispersed, micrometer-sized, and oppositely charged microgels were synthesized by aqueous free-radical precipitation polymerization by using N-isopropylmethacrylamide, comonomers, and cross-linkers. The oppositely charged microgels were prepared by using different types of water-soluble initiators. These microgels were mixed in a solution to assemble them at the air/water interface. In particular, linear and branched chainlike structures of the microgels were spontaneously formed at the air/water interface. Effects of salt concentration, microgel concentration, and number ratio of cationic and anionic microgels on the structures of microgel assembly were investigated by optical microscopy and scanning electron microscopy.