A series of polyisobutenylsuccinimide derivatives, in which polyisobutenylene block with a definite chain length was linked with four different ethylenediamine end groups (diaminoethane, diethylenetriamine, triethylenetetraamine, and tetraethylenepentaamine), were synthesized and used to disperse TiO₂ nanoparticles in nonpolar solvent. The influences of the sizes of hydrophilic/hydrophobic groups on the dispersibility of TiO₂ nanoparticles were investigated, and it was found that: when the molecular weight of polyisobutenylene block was fixed at 2000, Zeta potentials of TiO₂ particles increased while their particle sizes decreased with the increasing of the length of ethylenediamine chain in the dispersants, implying that the interactions between the dispersant and TiO₂ nanoparticles became stronger. It was also disclosed that when the polyamine end group came to be tetraethylenepentaamine, polyisobutenylsuccinimide with a 2000 molecualr weight of polyisobutenylene block showed the best dispersing ability while compared to those with 1000 and 3000 molecular weights of polyisobutenylene segments. Thus, the most appropriate HLB (hydrophile-lipophile balance) value of the dispersant was estimated as around 2.5. The obtained TiO₂ nanoparticles treated with such a dispersant demonstrated good electrophoretic displays.

Key words: polyisobutenylsuccinimide, TiO₂ nanoparticles, dispersibility, HLB value, electrophoretic display