The compaction of TiO2 suspension as a negatively charged model suspension by using dual ionic thermosensitive polymers was investigated. First, a cationic thermosensitive polymer, poly (N-isopropylacrylamide-co-N,N-dimethylaminopropylacrylamide) was added to the TiO2 suspension followed by an anionic thermosensitive polymer, poly (N-isopropyl-acrylamide-co-acrylic acid). By adding the latter, a polymer complex with the cationic thermosensitive polymer adsorbed on the particle is formed, and charge neutralization occurs to decrease the transition temperature of the polymer adsorbed on the TiO2 particles. As a result, the compaction of the TiO2 suspended particles due to the hydrophobic interaction of the adsorbed polymers occurs at a relatively low temperature by applying an adequate mechanical force with a plunger. In order to initiate the compaction, it was necessary to cover the surface of the TiO2 particles sufficiently by the cationic thermosensitive polymer molecules, and the optimum dosage of the anionic thermosensitive polymer was observed. The transition temperature of the polymer complex adsorbed on the TiO2 particles was dependent on the ratio of the dosages of the cationic and anionic thermosensitive polymers. (C) 2008 Elsevier B.V. All rights reserved.